Search

Breeding success (fledglings pair−1 y−1) of the Red-listed African Black Oystercatcher (Haematopus moquini) is highly variable, both spatially and temporally. Despite a diversity of natural factors causing this variability, there is evidence that two anthropogenic factors, i.e. disturbance and an introduced mussel (Mytilus galloprovincialis), are having an impact on the local breeding success of this species. Using a data set comprising 87 site-years of nest-monitoring data across most of the species’ breeding range, we analysed the extent and causes of variability in breeding success. Breeding success differed across three population categories defined by varying levels of human disturbance: island populations, protected mainland populations, and unprotected mainland populations. Differences in breeding success between island populations and protected mainland populations were likely due to differing exposure to predators; however, differences between protected and unprotected mainland populations were unlikely caused by this as both experience equivalent predation levels (although from different predators). Protection only improved the breeding success of oystercatchers in very high-quality habitats (with a high biomass of alien mussels), and where populations were ‘released’ from high levels of human disturbance. In unprotected mainland areas, human activity impacted on the breeding success of local populations primarily through predation of small chicks by uncontrolled dogs, and by rising tides drowning chicks that were hiding from human disturbance. The findings of this study note the potential conservation dilemma resulting from an invasive species improving the conservation status of a Red-listed species, and encourage the implementation of restricted sites in high-quality habitats with high breeding pair densities.Keywords: breeding ecology, fledging success, hatching success, human impacts, predation

Data have been collected on the breeding success of several characteristic coastal breeding birds in the Wadden Sea each year since 2005. Ten birds species considered representative of specific habitats and food groups are being monitored. The monitoring scheme on breeding success in coastal breeding birds is run as an ‘early warning system’ to follow the reproductive capacity of the bird populations in the Wadden Sea and understand the processes underlying fluctuations in populations. It is a valuable addition to the monitoring of population numbers and is carried out under a trilateral agreement with Germany and Denmark (TMAP). The results from 2015–2016 and an analysis of data series from the period 2005–2016 (sometimes longer) show that several species on average reared too few young to sustain stable population size in many of these years, especially the Eurasian Oystercatcher, Pied Avocet, Common Tern and Arctic Tern, and in recent years also the Black-headed Gull, whose breeding success has significantly declined since 1995. Other species showing a significant decline in breeding success are the Spoonbill and Common Tern. The only species to show any significant improvement in breeding success since 2005 is the Lesser Black-backed Gull Sinds 2005 worden in de Waddenzee jaarlijks gegevens verzameld over het broedsucces van een aantal karakteristieke kustbroedvogels. Hiervoor worden tien vogelsoorten gevolgd die representatief worden geacht voor specifieke habitats en voedselgroepen. Het reproductiemeetnet kustbroedvogels wordt uitgevoerd als een ‘early warning systeem’ om het reproducerend vermogen van de vogelpopulaties in de Waddenzee te volgen en de achterliggende processen van populatieveranderingen te doorgronden. Het fungeert als een belangrijke aanvulling op de monitoring van aantallen en aantalsveranderingen en wordt uitgevoerd in het kader van trilaterale afspraken met Duitsland en Denemarken (TMAP). Uit de resultaten van 2015-2016 en analyse van gegevensreeksen uit de periode 2005-2016 (soms langer) blijkt dat een aantal soorten in veel jaren en gemiddeld genomen weinig jongen grootbrengen. Dit geldt vooral voor Scholekster, Kluut, Visdief en Noordse Stern, en in de afgelopen jaren ook voor Kokmeeuw, waarvan het broedsucces sinds 1995 significant is afgenomen. Andere soorten met een significant afnemend broedsucces zijn Lepelaar en Visdief. Alleen bij Kleine Mantelmeeuw was sinds 2005 sprake van een significante verbetering van het broedsucces.

Degradation of nesting habitat for coastal birds has led to the use of nontraditional nesting habitat. The American Oystercatcher (Haematopus palliatus) is listed as a “Species of High Concern” by the U.S. Shorebird Conservation Plan and is declining in the southern portion of its U.S. breeding range, where ∼50% of breeding oystercatchers nest on shell substrate instead of beachfront habitat. We measured daily survival rates during incubation and chick rearing in shell rake habitats over five breeding seasons in the Cape Romain region of South Carolina, USA. Of 354 nesting attempts monitored, 16.1% hatched at least one egg. During incubation, daily survival rate was 0.938, corresponding to 22.8% success to hatching (nest success). For broods, daily survival was 0.991, or 74.0% success from hatching to fledging. Productivity in the Cape Romain region is primarily being lost during the incubation phase, when nests are exposed to overwash and predation. Mobile chicks may, however, be able to avoid f...

Scale-appropriate, foundational datasets are necessary for ecological analyses of the rocky intertidal ecosystem. We used terrestrial laser scanning (TLS) to characterize and quantify the rocky intertidal zone topography at a western U.S. coastal site (Rabbit Rock, Oregon) to support ecological research relating to potential climate-induced changes in distribution and abundance of intertidal invertebrates and a large-bodied shorebird, the Black Oystercatcher (Haematopus bachmani). Alternate available data (e.g., aerial photography, airborne LIDAR) proved inadequate or infeasible for development of a topographic surface model inclusive of intertidal area from Mean Lower Low Water to Mean Higher High Water tidal elevation. Our TLS-derived topographic surface model competently supported development of an invertebrate distribution model relative to tidal elevation and topography. Using the developed model, we estimated current and future aerial extent of the intertidal zone and potential foraging habitat for Black Oystercatcher in our study area. Intertidal zone area decreased from 7,194 m2 to 6,409 m2 and 3,070 m2 with 1 and 2 m sea-level rise, respectively. Surprisingly, due to the configuration of site substrate, potential foraging habitat for Black Oystercatcher increased from 5,658 to 5,903 m2 with 1 m sea-level rise, but declined to 3,068 m2 with 2 m sea-level rise. Our results demonstrate the utility of TLS for ecological research in the rocky intertidal zone. They further illustrate that climate change effects on ecological conditions may vary considerably depending on local configurations.

The extensive literature on the African Black Oystercatcher is a testament to what is now a conservation success story. Here we provide the first genetic insight into the population dynamics of this recovering shorebird and an assessment of genetic variation within the species using microsatellite markers. Although behavioural studies suggest strong natal philopatry, we found a single genetic cluster across all of the locations sampled and a significant signal of isolation by distance suggesting some geographical structuring. The microsatellite markers used in this study are useful at a population level, and the limited genetic variation detected is likely to be due to a low historical population size.

The American oystercatcher (Haematopus palliatus palliatus) is currently listed as a species of high concern by the United States Shorebird Conservation Plan. Because nutritional status directly impacts overall health and reproduction of individuals and populations, adequate management of a wildlife population requires intimate knowledge of a species' diet and nutrient requirements. Fat-soluble vitamin concentrations in blood plasma obtained from American oystercatchers and proximate, vitamin, and mineral composition of various oystercatcher prey species were determined as baseline data to assess nutritional status and nutrient supply. Bird and prey species samples were collected from the Cape Romain region, South Carolina, USA, and the Altamaha River delta islands, Georgia, USA, where breeding populations appear relatively stable in recent years. Vitamin A levels in blood samples were higher than ranges reported as normal for domestic avian species, and vitamin D concentrations were lower than anticipated based on values observed in poultry. Vitamin E levels were within ranges previously reported for avian groups with broadly similar feeding niches such as herons, gulls, and terns (eg, aquatic/estuarine/marine). Prey species (oysters, mussels, clams, blood arks [Anadara ovalis], whelks [ Busycon carica ], false angel wings [ Petricola pholadiformis ]) were similar in water content to vertebrate prey, moderate to high in protein, and moderate to low in crude fat. Ash and macronutrient concentrations in prey species were high compared with requirements of carnivores or avian species. Prey items analyzed appear to meet nutritional requirements for oystercatchers, as estimated by extrapolation from domestic carnivores and poultry species; excesses, imbalances, and toxicities-particularly of minerals and fat-soluble vitamins-may warrant further investigation.

An organism's heart rate is commonly used as an indicator of physiological stress due to environmental stimuli. We used heart rate to monitor the physiological response of American Oystercatchers (Haematopus palliatus) to human activity in their nesting environment. We placed artificial eggs with embedded microphones in 42 oystercatcher nests to record the heart rate of incubating oystercatchers continuously for up to 27 days. We used continuous video and audio recordings collected simultaneously at the nests to relate physiological response of birds (heart rate) to various types of human activity. We observed military and civilian aircraft, off-road vehicles, and pedestrians around nests. With the exception of high-speed, low-altitude military overflights, we found little evidence that oystercatcher heart rates were influenced by most types of human activity. The low-altitude flights were the only human activity to significantly increase average heart rates of incubating oystercatchers (12% abov...

Sex-specific feeding segregation related to sexual bill dimorphism has been described in several oystercatcher species, including the African black oystercatcher. For the latter, studies concerned only a small number of breeding pairs and were done prior the invasion of the South African rocky shores by the Mediterranean mussel, which is believed to have benefited oystercatchers by increasing overall biomass. Here, we investigated geographic variability in the segregation of diet, biometrics and body condition between sexes in the African species, in relation to changes in foraging habitats along the South African coastline, using stable isotope analyses. Males and females and their potential prey (mussels, limpets, polychaetes and ascidians) were sampled on the southern African west, south-west and south-east coasts for stable isotope analyses and biometrics and body conditions of birds were measured. Bill dimorphism occurred throughout the study area and south-west males had lower body conditions than other males and females in general. Sexes displayed little differences in their δ 13 C ratios and in the relative consumption of the different prey throughout the study area, except on the south-east coast where males were slightly depleted in 13 C relative to females and the most abundant prey elsewhere (the Mediterranean mussel) is rare. Females were slightly but significantly enriched in 15 N by 0.3‰ compared to their breeding partners and this did not link clearly to differences in diet. We argue that the combined effect of biogeographic variations in rocky shores diversity and biomass, heterogeneous invasion by the Mediterranean mussel on the South African coastline and bill dimorphism may have altered the sex-specific feeding behaviour of oystercatchers differently between coastal regions and possibly had an additional cost for male oystercatchers faced with lower prey biomass and diversity on the south-west coast.

Rocky shores and beaches are important over-wintering areas for non-estuarine waders but have rarely been studied. We examined cliff top habitat use by 6 species of wader over 75 km of coast to assess their potential value as alternative feeding sites to rocky and sandy shores. Both the regional and local survey showed that waders occurred on golf courses and recreational grasslands in higher frequencies than expected but arable and pasture use was lower than expected. We also compared local wader densities on rocky and sandy shores, pastures, golf courses, caravan parks and recreational grasslands over two winters. Sanderling predominantly fed on the beach whereas Oystercatcher, Dunlin, Turnstone and Redshank numbers significantly increased on golf courses and recreational grasslands over the winter period, with pasture being rarely used. General linear models were used to relate environmental factors to the presence and absence of each species on the cliff top habitats. Redshank was the only species that showed a higher probability of occurrence on cliff top habitats at high tide whereas the probability of Turnstone, Oystercatcher and Redshank occurring increased as temperatures declined. Using core sampling, we determined that invertebrate richness and abundance was significantly higher on the recreational grasslands and golf courses than on the pasture or the beach. Our data demonstrated that cliff top habitats are important alternative feeding areas for over-wintering waders in areas where the intertidal is bounded by cliffs. Current management creates short sward, open field habitats with a diverse and abundant invertebrate food supply exploited by waders. Any alterations to the land use of these areas should be carefully considered by planning authorities in light of the fact that they support species that are of conservation concern.

The Manila clam Ruditapes philippinarum is one of the most commercially valuable bivalve species worldwide and its range is expanding, facilitated by aquaculture and fishing activities. In existing and new systems, the species may become commercially and ecologically important, supporting both local fishing activities and populations of shorebird predators of conservation importance. This study assessed potential fishing effects and population dynamics of R. philippinarum in Poole Harbour, a marine protected area on the south coast of the UK, where the species is important for oystercatcher Haematopus ostralegus as well as local fishers. Sampling was undertaken across three sites of different fishing intensities before and after the 2015 fishing season, which extends into the key overwintering period for shorebird populations. Significant differences in density, size and condition index are evident between sites, with the heavily dredged site supporting clams of poorer condition. Across the dredge season, clam densities in the heavily fished area were significantly reduced, with a harvesting efficiency of legally harvestable clams of up to 95% in this area. Despite occurring at significantly higher densities and growing faster under heavy fishing pressure, lower biomass and condition index of R. philippinarum in this area, coupled with the dramatic reduction in densities across the fishing season, may be of concern to managers who must consider the wider ecological interactions of harvesting with the interest of nature conservation and site integrity.

Anthropogenic disturbance can degrade the quality of stopover sites for migratory shorebirds. We investigated the potential effects of pedestrian traffic and shellfishing on foraging shorebirds at a key stopover site at Monomoy National Wildlife Refuge (Monomoy Refuge), Massachusetts, USA. We experimentally approached 11 species of shorebirds to quantify flight-initiation distances (FID) and found that species and age affected FID. Smaller Calidris sandpipers generally allowed pedestrians to approach within 25 m before flushing, whereas larger shorebirds (black-bellied plover [Pluvialis squatarola] and American oystercatcher [Haematopus palliatus]) had FID over 50 m. We also found that juveniles of all species had shorter FID than adults. Based on adult FID, we developed species-specific buffer distances for 11 species that ranged from 61 m for least sandpiper (Calidris minutilla) to 186 m for black-bellied plover. We also investigated the potential impacts of commercial and recreational shellfish harvesters, who rake for soft-shell clams (Mya arenaria) on mudflats where shorebirds actively foraged. Microhabitats with recent shellfishing activity had a positive influence on the density of 2 species (ruddy turnstone [Arenaria interpres], and American oystercatcher), whereas the presence of shellfishers did not appear to affect the density of other species of shorebird we monitored. We regularly detected black-bellied plovers and ruddy turnstones actively foraging in microhabitats where shellfishers had recently exposed sediment. Given the levels of shellfishing and pedestrian traffic at Monomoy Refuge, we found no evidence to suggest that current human activity has a strong negative impact on migratory shorebirds using Monomoy Refuge. However, if the amount of pedestrian traffic and shellfishing were to increase substantially, a buffer zone system might have to be implemented during peak migration periods to minimize impacts, with buffers >185 m from key foraging sites to reduce disturbance to the most sensitive species. © 2013 The Wildlife Society

We documented the diet of the Black Oystercatcher (Haematopus bachmani) on Haida Gwaii, British Columbia, Canada, (2004–2010) with prey remains from 99 territories in Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site. The ranking of its four main prey types did not vary annually. Numerically, the prey comprised 50–75% limpets, 14–34% mussels, 8–18% chitons, 1–2% Northern Abalone (Haliotis kamtschatkana), and

Non-indigenous Pacific oysters ( Crassostrea gigas ) have been invading the central Wadden Sea since 1998, predominantly settling on intertidal blue mussel ( Mytilus edulis ) beds which are increasingly transformed into Crassostrea -reefs. Pacific oysters are strong ecosystem engineers and the habitat change is considered to be a threat for waterbirds losing important feeding sites in the intertidal of the Wadden Sea. This study has increased our understanding of the use of foraging habitats by birds according to changing food resources. During the spring and autumn migration period in 2007, we recorded bird densities at two reef types varying in Pacific oyster density and at the adjacent sand flat as a reference site. We also recorded feeding behaviour, choice of prey and assessed peck and intake rate of three target species: Eurasian oystercatcher Haematopus ostralegus , Eurasian curlew Numenius arquata and European herring gull Larus argentatus . To evaluate the use of the Crassostrea -reef in the central Wadden Sea, we compared bird densities of the target species at different intertidal feeding habitats in various regions and compared the biomass intake of Eurasian oystercatcher feeding on different prey species. We show that Eurasian oystercatcher and Eurasian curlew have adapted to the new situation and learned to exploit the food supply offered by Crassostrea -reefs. While foraging mainly on Pacific oysters, Eurasian oystercatchers attained sustainable intake rates even though food resource at dense reef during autumn was very poor due to a lack in harvestable oysters. Consolidation of reefs limits the accessibility of prey for Eurasian oystercatchers whereas a successful recruitment of Pacific oysters enhances the suitability of the habitat. Eurasian curlew was promoted by the engineering effects of the Pacific oyster while feeding extensively on shore crabs at the reefs. In contrast, European herring gulls appear hampered in foraging during low tide and hereby negatively affected by the habitat change from Mytilus -beds to Crassostrea -reefs.

Nest failure has often been identified as a factor affecting American Oystercatcher (Haematopus palliatus) survivorship. To examine causes of nest failure, small digital cameras were deployed between 6 April and 15 July 2005 on American Oystercatcher nests on Fisherman Island National Wildlife Refuge located in Northampton County, Virginia. Twenty-five attempts, representing 22 different pairs, were recorded resulting in 7,570 hr of video footage. Nest survivorship was 44% (n = 11). High tide events associated with coastal storms were the largest source of nest loss (24%, n = 6), followed by predation on eggs (16%, n = 4). Nest abandonment, unknown factors, and infertile eggs accounted for the remaining 16% (n = 4) of nests. The main predator was Fish Crows (Corvus ossifragus). While American Oystercatchers were incubating, 211 instances were recorded where individuals of 22 species entered the field of view of video cameras. The most common species entering included Boat-tailed Grackle (Oidscal...

Climate variability and the rapid warming of seas undoubtedly have huge ramifications for biological processes such as reproduction. As such, gametogenesis and spawning were investigated at two sites over 200 km apart on the south coast of Ireland in an ecosystem engineer, the common cockle, Cerastoderma edule. Both sites are classed as Special Areas of Conservation (SACs), but are of different water quality. Cerastoderma edule plays a significant biological role by recycling nutrients and affecting sediment structure, with impacts upon assemblage biomass and functional diversity. It plays a key role in food webs, being a common foodstuff for a number of marine birds including the oystercatcher. Both before and during the study (early 2010–mid 2011), Ireland experienced its two coldest winters for 50 years. As the research demonstrated only slight variation in the spawning period between sites, despite site differences in water and environmental quality, temperature and variable climatic conditions were the dominant factor controlling gametogenesis. The most significant finding was that the spawning period in the cockle extended over a greater number of months compared with previous studies and that gametogenesis commenced over winter rather than in spring. Extremely cold winters may impact on the cockle by accelerating and extending the onset and development of gametogenesis. Whether this impact is positive or negative would depend on the associated events occurring on which the cockle depends, that is, presence of primary producers and spring blooms, which would facilitate conversion of this extended gametogenesis into successful recruitment.

Data collected in ten years (2003–2012) on Triangle Island, British Columbia, Canada were used to test the hypothesis that the annual breeding effort of black oystercatchers ( Haematopus bachmani ) declines with increasing spring sea-surface temperature. In all ten years, between nine and 15 oystercatcher pairs laid eggs in May and June, and as predicted, the number of active nests was negatively correlated with the mean sea-surface temperature in April. However, contrary to prediction, neither mean clutch size nor mean egg size declined with temperature. Clutches composed of just a single egg, probably indicative of recruitment by inexperienced females, appeared only in the five years with sea-surface temperatures below 9 °C. A reduction in the breeding propensity of individual females, rather than increased rates of mortality or emigration, better explained why fewer oystercatcher pairs bred in warm-water years. We infer that the breeding propensity of oystercatchers is indirectly affected by sea-surface temperature, mediated by effects of temperature on the behavior and physiology of the birds' invertebrate prey. Our results suggest a novel mechanism by which ocean warming might affect predator–prey interactions in intertidal ecosystems.

In this study we examined the effect of different livestock grazing treatments on breeding bird densities in a salt marsh habitat. To avoid an experiment on the large scale needed to directly measure grazing effects on bird densities, we followed a two-step approach. First, we measured vegetation micro-patterns (mosaic of lower vegetation and taller patches at 4x4 m) around Common Redshank Tringa totanus and Eurasian Oystercatcher Haematopus ostralegus nests and at random sites paired with these nests sites to judge suitability of micro-patterns for nest building. Secondly, we measured micro-patterns at 120 permanent plots in five different experimental grazing treatments to determine how grazing affects micro-patterns. We compared low stocking density of both cattle and of horses, high stocking density of cattle and of horses, and intermittent grazing with a high stocking density of cattle (i.e. yearly intervals of grazing and no grazing). Redshank and Oystercatcher nests occurred in sites with taller vegetation and more pronounced micro-patterns than found at random sites. Paddocks grazed with low densities of livestock or with a high density intermittent grazing treatment had micro-patterns preferred by the birds. We conclude that Redshanks and Oystercatchers may benefit in terms of potential nest sites from grazing at low livestock densities or at intermittent stocking densities through effects of grazing on micro-patterns in the vegetation.

The spatial distribution of foraging animals at a given time simultaneously depends on (1) exogenous environmental variables such as resource availability and abiotic habitat characteristics, and (2) the endogenous variable social aggregation made up of the opposing mechanisms of conspecific attraction and repulsion. We developed an exogenous environment-social aggregation model to analyse the spatial distributions of six abundant shorebird species in the Dutch Wadden Sea at resolutions of 150 x 150, 200 x 200 and 250 x 250 m. We used these resolutions to check the robustness of the estimates to the modifiable areal unit problem. We estimated the model parameters by spatial autoregression. This approach enables, among others, estimation of the direct and indirect effects of an exogenous environmental variable on animal density. The former is given by the regression coefficient and the latter, which is due to the amplification of the direct effect by social aggregation, by the spatial multiplier. At all resolution levels and for all species, the explanatory power of social aggregation, measured by Nagelkerke R-2, was larger than the combined contribution of the exogenous environmental variables food availability, silt content and mudflat elevation. Social aggregation was stronger for dunlin, Calidris alpina, red knot, Calidris canutus, and curlew, Numenius arquata, than for oystercatcher, Haematopus ostralegus, grey plover, Pluvialis squatarola, and bar-tailed godwit, Limosa lapponica. The total impacts (that is, direct effect plus all indirect impacts) of the exogenous environmental predictors tended to exceed substantially the direct effects (which tend to be the only ones examined in studies on foraging distributions). (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The relationship between foraging shorebirds, macrobenthos and sedimentary parameters has been widely studied across Western Europe. Megatidal areas have large zones uncovered when the water retreats. Consequently, in such cases, the tide also influences foraging activities. This paper examines the use of an intertidal space by waders to define how macrobenthic resource concentrates foraging activity of birds in a large megatidal sandflat. This approach combines accurate spatial distribution of waders (Oystercatcher, Eurasian curlew, Bar-tailed Godwit and Redknot) according to their activity with ecological/biological parameters. A differential exploitation of the flat is clearly shown, with macrobenthic biomass appearing as one of the main explanatory factor for the four species considered on the western part of the bay and altitude (shore elevation) in the eastern part. The novelty of this study relates to the large area, also presumed to be a functional unit, while considering at the same time the singularities of the different parts of the flat. This multi-scale approach identifies important factors influencing the differential distribution patterns observed. The different selected parameters present an important variability in their contribution, underlining the complexity of explaining the distribution of foraging birds. Consequently, the study of such complex phenomena needs to consider additional variables to improve the relevance of explanatory models.

Birds’ responses to human disturbance are interesting due to their similarities to anti-predator behaviour, and understanding this behaviour has practical applications for conservation management by informing measures such as buffer zones to protect priority species. To understand better the costs of disturbance and whether it will impact on population size, studies should quantify time-related responses as well as the more commonly reported flight initiation distance (FID). Using waders wintering on an estuarine area, we experimentally disturbed foraging birds on the Wash Embayment, UK, by walking towards them and recording their responses (FID, alert time, time spent in flight, time taken to resume feeding, and total feeding time lost). We present data for 10 species of conservation concern: Curlew Numenius arquata, Oystercatcher Haematopus ostralegus, Bar-tailed Godwit Limosa lapponica, Grey Plover Pluvialis squatarola, Redshank Tringa totanus, Knot Calidris canutus, Turnstone Arenaria interpres, Ringed Plover Charadrius hiaticula, Sanderling Calidris alba and Dunlin Calidris alpina. Larger species responded more strongly, response magnitude was greater under milder environmental conditions, and responses varied over both small and large spatial scales. The energetic costs of individual responses, however, were low relative to daily requirements and disturbance events were unlikely to be frequent enough to seriously limit foraging time. We suggest, therefore, that wintering wader populations on the Wash are not currently significantly negatively impacted by human disturbance during the intertidal foraging period. This is also likely to be the case at other estuarine sites with comparable access levels, visitor patterns, invertebrate food availability and environmental conditions.

Many ground-nesting shorebirds experience a high level of anthropogenic disturbance, often to the detriment of their breeding success. This study investigated the responses of the Near-Threatened African Black OystercatcherHaematopus moquini (ABO) and the Least Concern Kelp Gull Larus dominicanus vetula (KG) to anthropogenic disturbance during the pre-breeding and breeding season at three locations differing in levels of anthropogenic disturbance and colony size. Birds were directly approached from over 100 m away and markers were dropped at each behavioural reaction to the approach. Measuring back allowed a quantitative measure of the effects of disturbance. Stand response distances in breeding ABO were location sensitive, which related to disturbance level, showing that they stood up earlier in a highly disturbed location. Neither ambient conditions (wind speed and ambient temperature) nor nesting condition (egg age and clutch size) played a significant role in responses. Interestingly, breeding KG behaviour was affected by location, to a lesser extent by clutch size, but not by ambient conditions. Both ABO and KG significantly altered their behavioural responses to disturbance from pre-breeding to breeding. These results emphasise the need to have a buffer zone surrounding breeding areas excluding human presence to allow for the successful breeding of ABO.Keywords: African Black Oystercatcher, buffer zone, Kelp Gull, manipulated disturbance, urbanisation

Orford Ness is an isolated 1551-acre shingle spit facing the North Sea, off the Suffolk coast of Great Britain. On the one hand, the place offers a distinct and spectacular experience of humanity’s relations with external nature. The site is about 2000 acres in size and is a rare but fragile environment for rare bird, plant, and insect life. Avocet, hawk, redshank, oystercatcher, and many other migratory waders all breed there and it is the largest vegetated shingle spit in Europe with a very wide range of rare plant life (National Trust 2003). It is now protected as an Environmentally Sensitive Area, a Site of Special Scientific Interest, and an Area of Outstanding Natural Beauty.

Large-scale monitoring of bird populations is often based on count data collected across spatial scales that may include multiple physiographic regions and habitat types. Monitoring at large spatial scales may require multiple survey platforms (e.g., from boats and land when monitoring coastal species) and multiple survey methods. It becomes especially important to explicitly account for detection probability when analyzing count data that have been collected using multiple survey platforms or methods. We evaluated a new analytical framework, N-mixture models, to estimate actual abundance while accounting for multiple detection biases. During May 2006, we made repeated counts of Black Oystercatchers (Haematopus bachmani) from boats in the Puget Sound area of Washington (n = 55 sites) and from land along the coast of Oregon (n = 56 sites). We used a Bayesian analysis of N-mixture models to (1) assess detection probability as a function of environmental and survey covariates and (2) estimate total...

The breeding biology of the Black Oystercatcher (Haemotopus bachmani) was studied on Triangle Island, British Columbia, Canada in 2003–2011. Breeding density at this remote site was relatively high, ranging from 2.23 to 3.72 pairs/km of shoreline in the 9 y. Most clutches were initiated in the last 2 wk of May, and the annual mean 1st clutch size ranged from 2.1 to 2.8 eggs/nest, values similar to those recorded at other sites. Egg size differed little in clutches of 1, 2, and 3 eggs. Hatching success at Triangle Island ranged from 55 to 87% in 5 y, which is on the high end of the range compared to other sites. Limited data suggested that adult survival rates exceeded 90% per annum, and 43% of individuals banded just prior to fledging survived through at least their 1st winter. Oystercatchers are reliable indicators of the health of coastal ecosystems, and these data comprise a baseline against which future changes at Triangle Island can be assessed.

Studies examining the effects of human disturbance on avian parental behavior and reproductive success are fundamental to bird conservation. However, many such studies fail to also consider the influence of natural threats, a variable environment, and parental roles. Our work examines interactive relationships of cyclical (time of day, tide, temperature, seasonality) and stochastic (natural/human disturbance) processes with incubation patterns (attendance, bout lengths, recess rates) of the Black Oystercatcher (Haematopus bachmani), a shorebird of conservation concern. We used 24-hr-per-day video monitoring of 13 molecularly sexed breeding pairs to systematically examine incubation, revealing previously undocumented information that may inform conservation practices for the genus. Seven of 22 video-monitored nests failed, primarily from egg depredation by nocturnal mammals. Analyses of 3177 hr of video footage indicated a near doubling of incubation-bout lengths at night, corresponding to the in...

When feeding on blue mussels (Mytilus edulis), oystercatchers (Haematopus ostralegus) either stab into the mollusc’s gaping valves or hammer through its dorsal or ventral shell. Whilst the selectivity of hammering and stabbing oystercatchers for specific prey morphologies has been well studied, the way in which the effects of environment on M. edulis morphology can in turn affect feeding methods of H. ostralegus is very poorly understood. Based on morphological analyses on randomly selected shells from three intertidal zones, this study failed to detect differences in morphology or distribution of dorsally and ventrally hammered shells but confirms the finding of previous authors that hammering oystercatchers select thinner mussels than stabbing birds. Additionally, we show that this difference in optimal prey morphology can lead to spatial patterns in oystercatcher feeding behaviour. Whilst at the low intertidal and higher mid intertidal zones, characterised by comparatively thick shells, most empty shells had apparently been stabbed, hammering was the dominant feeding behaviour at the lower mid intertidal zone, where shells were thinner. Preference of hammering birds for smaller mussels was not ubiquitous. Sagittal shell shape was predominantly influenced by allometric growth effects and had only minor effect on prey selection. All oystercatchers preferred less inflated mussels, with the degree of shell inflation gradually increasing with higher intertidal elevation. Our results illustrate the importance of small-scale patterns in prey ecophenotypes in determining the distribution and feeding dynamics of wading birds.

Predators are able to identify fine characteristic features of prey and use them to maximise the profitability of foraging. Oystercatchers Haematopus ostralegus select thin-shelled mussels Mytilus edulis to hammer through because they are easier to crack than thick-shelled mussels. But mussel shells are composite structures, so we need to ask what it is about these thin-shelled mussels that make them vulnerable. Here we show that the mussels damaged by Oystercatchers were mainly distinguished by having a significantly thinner prismatic layer than undamaged mussels. Regression analysis indicated that the Oystercatchers' shell selection was independently influenced by the thickness of the prismatic and nacreous layers, but the coefficient for the thickness of the prismatic layer was almost one and a half times that for the nacreous layer. Thus the thickness of the prismatic layer largely determines the vulnerability of the mussel shells. Oystercatchers were more likely to attack mussels by the right valve than the left, and this tendency was accentuated in larger mussels and those with a thicker nacreous layer.

Male and female sooty oystercatchers (subspecies Haematopus fuliginosus fuliginosus; Haematopodidae) have an average difference in bill length of 19%. We studied the relationship between this sexual dimorphism and foraging ecology at coastal sites in southern New South Wales, Australia. Intersexual foraging divergence was most striking in diet, with seven prey classes eaten exclusively by one sex (male: 4, female: 3), and all shared prey classes eaten in different proportions. Intersexual diet partitioning was also observed in energetic rewards gained from foraging, with females gaining highest energetic benefits from eating ascidians and males from eating limpets. Furthermore, within the most commonly consumed prey item, limpets, females gained higher energetic benefit from eating smaller sizes while males gained greater rewards from the largest limpet sizes. Intersexual divergence was also observed in several aspects of foraging behaviour. Finally, there was a significant effect of tidal cycles upon intersexual niche partitioning in this species; the degree of diet divergence varied between tide conditions and females had a consistently more efficient dietary intake on neap tides than males. Diet divergence in the sooty oystercatcher is greater than previously observed in any oystercatcher, and is correlated with the largest sexual bill dimorphism recorded in this family. It is argued that intersexual competition between territorial pairs is operating to diverge male and female bill morphology.

Estimating the spatial position of birds in open habitats like intertidal mudflats is important for many studies, for example, detailed density estimates or linking predation pressure to resource availability. To date, several methods have been used to estimate the positions of birds, including density counts in predetermined plots, range finders, photography, and tracking individuals tagged with GPS-equipped transmitters, and each method has advantages and shortcomings. Counts in premarked plots are possible over relatively long distances, but small-scale information is lost due to within-plot averaging. Other methods accurately determine the position of individuals, but can only be used at relatively short distances or involve capturing birds. We describe a simple and low-cost method to estimate the spatial position of individual birds in open habitats using a telescope-mounted instrument that measures the scope's viewing angle. Using this Telescope-Mounted Angulator (TMA), the distance to focal birds can be calculated by simple trigonometry, requiring only the viewing angle and mounting height of the telescope. Laboratory tests revealed that the TMA was most accurate when calibrated for individual observers. Field experiments performed on a 4-m high observation platform showed that the TMA can estimate the position of shorebirds with an accuracy of 18 to 36 m up to a distance of 500 m. By also including the direction, determined with a compass, the spatial position of birds can be reliably estimated. The TMA can be a valuable tool for estimating the spatial position of animals in various flat landscapes, providing detailed measurements in a relatively short period of time.

Parasitological investigations on 40 gulls ( Larus ), 15 eiders ( Somateria ) and some birds of shelduck ( Tadorna ), curlew ( Numenius ), oystercatcher ( Haematopus ) and terns ( Sterna ) resulted all in all 7 coccidia and about 76 helminth species, partly residenting in different hosts and often in enormous quantities ( Somateria 160.000, Tadorna 58.000, Larus 62.000, Numenius 93.000). Effects of helminthal loads upon the avian hosts, biology of parasites and correlations between their coastal and inland places of residence are in discussion. Morphological differences of Psilochasmus in Tadorna tadorna , of Gymnophallus from gallbladders of Larus too, furthermore the structural change of egg-forming Gymnophallida in the gut of Somateria mollissima and coccid oocysts from kidneys of Larus argentatus , Haematopus ostralegus, Tadorna tadorna and Somateria mollissima are showed.

This essay deals with Weather Station, an extended installation on the west shore of Morecambe Bay. Started in 2008 it reflects the relationship between ecology, perception and performance in the liminal space between land and sea. Built on the edge of a beach Weather Station is a holistic artwork. As part of this project Fox discusses The Oystercatcher's Tale, a fable about global warming which forms part of The Bay Trilogy, a group of three visual poems/films.

This study was conducted between March and July of 2010 in the area of Yubudo (Is.) in order to assess its avian fauna. A total of 39,121 counts of 37 species were observed over 5 sessions. Important dominant species included the dunlin (Calidris alpine) (48.0%), followed by the bar-tailed godwit (Limosa lapponica) (26.2%), far eastern curlew (Numenius madagascariensis) (5.2%) and the great knot (Calidris tenuirostris) (5.1%). Among the dominant species, the dunlin and the bar-tailed godwit showed significant increase in count, while the great knot showed a decrease. The far eastern curlew, eastern oystercatcher (Haematopus ostralegus) and the Indian curlew (Numenius arquata) did not show any significant difference when compared to previous studies, in terms of both migratory bird count and migratory pattern. Such migratory pattern of dominant species seems to be the result of large scale environmental changes.

Detailed knowledge on species–habitat relationships is of crucial importance for the understanding of processes in marine ecosystems. Being top-predators, birds are important bio-indicators for marine systems. The aim of this study was to elucidate precise information on foraging habitat use and foraging times of oystercatchers (Haematopus ostralegus) on wide tidal flats using global positioning system (GPS) data loggers. The study was conducted to collect hints for the negative population trends in oystercatchers in the Wadden Sea. It is the first time that GPS technique has been used in a shorebird species. Although oystercatchers are known to exhibit foraging site fidelity, a number of individuals visited multiple sites. Foraging trips at night were longer, and the targeted sites were further away than those used during the day. These patterns were likely to be caused by higher risks of clutch predation by avian predators during the day that led adults to reduce their absence to defend their clutches. Our methodological approach enabled the subtle spatio-temporal patterns of habitat use to be determined on a very fine spatio-temporal scale. We suggest further potential studies using GPS data loggers that may help to reveal the reasons for the current declines in oystercatcher populations in the German Wadden Sea.

We use an individual-based model to assess the conservation objectives for knot Calidris canutus L. and oystercatcher Haematopus ostralegus L. on the Burry Inlet Special Protection Area (SPA), UK. Population monitoring has identified a decline in oystercatcher numbers, but cannot determine whether this is due to a decline in site quality. Long term data on cockle stocks show that the biomass of the large-sized cockles consumed by oystercatcher declined after 2004, whereas a similar decline was not observed in the smaller cockles consumed by knot. The model postdicts that during the winters of 2005/2006 to 2008/2009 the site was unable to support the number of oystercatcher present at the time it was designated (i.e. the SPA population). Large cockle biomass remained low during 2009/2010, but increases in mussel biomass meant that the model postdicted that the site could support the SPA population of oystercatcher. Knot food supplies remained high during most years, except 2008/2009 during which the model postdicted that the SPA population could not be supported. The model postdicted that the stock reserved for oystercatchers after shellfishing needed to be 2-4 times the amount consumed by the birds in order to support the bird population. We recommend that where necessary, the conservation objectives of waterbirds should be assessed using a combination of thorough population size and behaviour monitoring to identify sites with population declines, and individual-based modelling on these sites to determine whether reduction in site quality may contribute to the site-specific population decline.

Flight initiation distances (FIDs) were measured for nine wader species at the Venice lagoon (Italy), one of the most important sites for waterbirds around the Mediterranean. The response (277 instances) to boat and pedestrian disturbances caused outside the breeding season was observed. FID was positively and significantly correlated with the mean body size of the species. The correlation between FID and flock size was also positive and significant, irrespective of the type of disturbance. FID values ranged from 27.9 + 15.6 m (mean + SD, N = 32) in Common Snipe to 140.4 + 48.1 m (N = 30) in Eurasian Curlew, pooling data for both disturbance types. The same ranking was observed if pedestrian and boat disturbances were considered separately; differences were species-specific. For six species, the data allowed comparisons to be made between boat- and pedestrian-evoked FID; the observed differences were not significant. Thus, boat disturbances during the non-breeding season did not evoke a stronger response among waders, in terms of FID, compared to pedestrians. According to these results, set-back distances, expressed as mean FID + 2 SD, are suggested to reduce the effects of man-made disturbances to waterbirds at a local scale. These distances range from 59-74 m for the most confiding species (Common Snipe, Kentish Plover and Ruddy Turnstone) to 121–267 m for the most wary (Eurasian Oystercatcher, Grey Plover and Eurasian Curlew). To protect the multi-specific and often large winter roosts from disturbance caused by pedestrians or boats, a higher set-back distance, 270 m, is suggested. —Scarton, F. (2018). Disturbance of non-breeding waders by pedestrians and boats in a Mediterranean lagoon. Ardeola, 65: 209–220.

We apply decision theory in a structured decision-making framework to evaluate how control of raccoons (Procyon lotor), a native predator, can promote the conservation of a declining population of American Oystercatchers (Haematopus palliatus) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oystercatcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers.

The American Oystercatcher (Haematopus palliatus palliatus) is the only species of oystercatcher native to the Atlantic coast of North America and is restricted in distribution to intertidal shellfish beds in coastal areas. Currently, the American Oystercatcher population in South Carolina and Georgia is threatened by widespread habitat loss, resulting in low reproductive success and small population size. Oystercatchers could be an important indicator of ecosystem health because they depend on quality coastal breeding habitat and prey on bivalves, which can accumulate toxins and pathogens from the local environment. Data were collected from American Oystercatchers (n=171) captured at five sites in South Carolina and Georgia between 2001 and 2006. Iridial depigmentation was frequently noted during physical examination and was more prevalent in female birds. Female birds were larger than males on average, but ranges for weight and morphometric measurements had considerable overlap. Mean values were calculated for hematology, plasma biochemistry, and hormone levels, and prevalence of exposure to select pathogens was determined. Mercury was the only trace metal detected in blood samples. These data provide baseline health information needed for longitudinal monitoring and conservation efforts for American Oystercatchers. In addition, this study illustrates the potential use of this species as an indicator for the health of the southeastern US coastal nearshore ecosystem.

Summary 1. Climate change encompasses changes in both the means and the extremes of climatic variables, but the population consequences of the latter are intrinsically difficult to study. 2. We investigated whether the frequency, magnitude and timing of rare but catastrophic flooding events have changed over time in Europe’s largest estuary. Subsequently, we quantified how this has affected the flooding risk of six saltmarsh nesting bird species. 3. We show that maximum high tide has increased twice as fast as mean high tide over the past four decades (0AE 8v s. 0AE 4c m year )1 ), resulting in more frequent and more catastrophic flooding of nests, especially around the time when most eggs have just hatched. 4. Using data on species’ nest elevations, on their timing of egg-laying and on the duration that their eggs and chicks are at risk from flooding, we show that flooding risks increased for all six studied species (even after accounting for compensatory land accretion) and this is expected to worsen in the near future if they do not adapt. Moreover, our study provides the first evidence that increasing flooding risks have reduced the reproductive output below stable population levels in at least one species, the Eurasian oystercatcher Haematopus ostralegus. 5. Sensitivity analyses show that currently birds would benefit most from adapting their nest-site selection to higher areas. However, historically the lower marsh has been favoured for its proximity to the feeding grounds and for its low vegetation aiding predator detection. 6. Synthesis and applications. We argue that it is more difficult for birds to infer that habitat quality has decreased from changes in the frequency of rare and unpredictable extreme events than from trends in climatic means. Consequently, at present the lower parts of the saltmarsh may function as an ecological trap. The creation of new (i.e. low) saltmarshes – currently a restoration priority – may thus counteract the goal of increasing the avian biodiversity of an area. Management tools to mitigate the effects of climate change, either by making the higher saltmarsh more attractive (mowing, predator control) or by reducing the flooding risk of the lower marsh (building elevated plots), await to be tested.

We assessed the blue mussel Mytilus edulis fishery management scheme introduced in 1994 in the Danish Wadden Sea that regulate fishing vessels, fishery quota, set-aside for mussel-eating birds and established zones closed to mussel fishery. The results showed (i) a reduction in the blue mussel biomass and mussel bed areas in zones closed to fishery, (ii) decrease in eiders Somateria mollissima numbers and increase or stable numbers for oystercatcher Haematopus ostralegus and herring gull Larus argentatus and (iii) that energy estimations based on ecological food requirements for the mussel-eating birds should be at least three times larger, than the amount set-aside in the mussel management scheme. It is concluded that the mussel management scheme had been unable to stabilize or increase the blue mussel stocks and to secure stable or increasing numbers for all target bird species. Thus, it is recommended to revise the present blue mussel management scheme in the Danish Wadden Sea, to continue and improve mussel stock and bird surveys, and to consider novel studies of the mussel-eating birds' energetics for improved set-aside estimates and future assessments.

Summary 1. Overexploited fisheries threaten many species that depend on the exploited resource. Shorebird populations are in decline globally and here we describe how changing shellfishery management and nutrient inputs have had dramatic influence on waterbird communities on an internationally important wetland. 2. Cockle Cerastoderma edule and mussel Mytilus edulis fisheries conflict with shorebirds by removing prey and increasing mortality amongst non-target benthic invertebrates. Under intense dredging pressure, evidence suggests that benthic invertebrates such as worms, with rapid growth and shortgeneration times, should predominate over species such as bivalves, with slower growth and longer generation times. 3. We investigated the change in the waterbird assemblage in the Wash, eastern England, between 1981–1982 and 2002–2003. This period was characterized by heavy fishing pressure on mussels and cockles, ultimately leading to a crash in the mussel stocks. 4. During the study period, the waterbird assemblage underwent a gradual change from one dominated by those species with a high proportion of bivalves or other prey (e.g. crustaceans, fish) in their diet to those with a higher proportion of worms. This gradual change was punctuated by major shifts, corresponding to three winters when oystercatcher Haemotopus ostralegus mortality was 5–13 times normal winter levels. 5. Oystercatcher, knot Calidris canutus and shelduck Tadorna tadorna showed the highest levels of decline. Since the last major oystercatcher mortality event in 1996–1997, the assemblage has not shifted back to that observed prior to the major crash in the mussel stock in 1992. 6. Changes in the waterbird assemblage were significantly related to mussel and cockle stock levels and, to a lesser extent, nutrient levels. Although correlative, evidence from this study indicates that fisheries caused shifts towards a waterbird community dominated by species with a high proportion of worms in their diet. 7. Synthesis and applications. Mechanical shellfisheries directly conflict with the nature conservation interest of sites holding internationally important waterbird populations. Removal of the mussel beds in the Wash led to major shifts in the waterbird assemblage, with a shift towards worm-feeders. Setting annual quotas that provide sufficient food for shellfish eating birds is essenti al to maintain the favourable status of this and other internationally important wetlands where shellfish are exploited.

Eurasian Oystercatchers Haematopus ostralegus ostralegus are a classic example of individual feeding specialization. Feeding specialization causes morphological differentiation in Oystercatchers' bill shapes due to varying degrees of abrasion associated with specific handling techniques for each prey species. Consequently, the Oystercatcher's bill shape has been used as a proxy for diet specialization, as it provides a quick and easy way to assess the diet choice of this marine top-predator. However, bill shapes of Oystercatchers are categorized visually in distinct types, while it has been argued that the relevant variation is continuous. Also, it is unclear how comparable the bill-shape classification is among studies and between the sexes and how universal bill shape-diet relationships are. Here we investigate the usefulness of bill-shape types as a proxy for diet choice in Oystercatchers, using four new and two published datasets. We show that quantitative bill-morphometrics provide no evidence that b...

Black Oystercatchers (Haematopus bachmani) have been identified as a species of concern by government agencies and conservation organizations because they have small populations and are sensitive to disturbance caused by shoreline and near-shore human activity. Expanding human recreation in Prince William Sound (PWS) may have potential negative consequences on Black Oystercatcher reproduction and on the population as a whole. Almost 2000 km of shoreline in western PWS was inventoried to assess density, distribution and habitat use of breeding Black Oystercatchers each June and July from 2001 to 2004. These efforts identified 94 territories (density 0.030.38 pairs/km). Black Oystercatcher territories were preferentially located on wave-cut platforms and rocky islets as well as gravel beaches but they avoided salt marsh, tide flats and sheltered rocky shores. Within western PWS 186 shoreline campsites were documented and people preferred to camp on gravel beaches. The association between campsites...

Aim Many wader populations around the world are declining as a consequence of habitat degradation or loss. It is therefore important to identify species-specific habitat demands accurately and to define the important factors explaining species distribution, in order to develop tools that can be used in conservation planning. The aim of this study is to create reliable, functional and ecologically interpretable predictive distribution models for five breeding wader species. Location The archipelago of SW Finland in the Baltic Sea. Methods We used multivariate adaptive regression splines (MARS) to create single-species and multiresponse distribution models based on 525 study islands and 12 abiotic and biotic environmental variables. Model evaluation was carried out on independent data not used in model building (100 + 116 islands). The models were tested for discrimination with receiver-operating characteristic statistics and for calibration with Millers calibration statistics (MCS). Results The single-species models for the turnstone (Arenaria interpres), redshank (Tringa totanus) and oystercatcher (Haematopus ostralegus) showed good predictive abilities, regarding both discrimination and calibration, when evaluated on independent data. The multiresponse models for the less prevalent species, common sandpiper (Actitis hypoleucos) and the common ringed plover (Charadrius hiaticula) had better discriminative abilities than the single-species models. The most influential predictor overall was occurrence of small larids. Exposure, area of forest and low and flat areas were also important, as well as shore habitats. Main conclusions We found that the ability of MARS to fit non-linear and multiresponse models makes it a useful method to quantitatively relate species occurrence to environmental characteristics of a complex environment.

Conservation management of Chatham Island oystercatcher (Haematopus chathamensis) nests was carried out between 1998 and 2004 on the Chatham Islands, New Zealand. Video monitoring during three breeding seasons (1999–2001) from 21 managed and 28 unmanaged nests revealed that feral cats (Felis catus) and an introduced rail, the weka (Gallirallus australis hectori), were the main predators, responsible for 68 and 16% of fatal events respectively. Other fatal events resulted from predation by a red–billed gull (Larus novaehollandiae scopulinus), tidal overwash, and a sheep (Ovis aries). Each accounted for c. 5% of fatal events. Daily survival rate and nest survival probability for 126 oystercatcher nests varied with management, but was unrelated to year or use of video monitoring. Daily survival rate for nests in managed and unmanaged areas was 0.990 (95% CI: 0.985 to 0.994) and 0.959 (95% CI: 0.941 to 0.971), respectively. Nest survival probability was 0.757 (95% CI: 0.652 to 0.834) in managed areas...

We investigated the growth of African black oystercatcher Haematopus moquini chicks on Robben Island, South Africa, over three austral summers, 2001-2004. Using a robust regression analysis to determine the growth parameters of chicks of known and unknown age we found that oystercatchers from our study population had a Gompertz growth rate coefficient that was 2% less than predicted for body mass based on the equation for waders. Leg growth lagged initially, then increased and slowed again as the chicks became older, whereas wing growth was slow initially but increased with age. Chicks with small growth rate coefficients for body mass exhibited retarded growth of all body measures except wing length. This enabled these chicks to fledge in a shorter period of time than their slow growth would otherwise allow. The growth rate of body mass was observed to vary greatly between chicks. Fast-growing African black oystercatchers had a shorter pre-fledging period; were larger at fledging and were more likely to fledge successfully. African black oystercatchers display sibling rivalry, and once a dominance relationship is established, the larger chick remains so during the pre-fledging period. Larger siblings fledged earlier and at a heavier mass than the smaller siblings and this may improve their chances of survival. Neither hatching date nor brood size influenced the growth rate coefficients.

Waterbirds migrating through and wintering in the Wadden Sea depend on undisturbed roost sites close to their feeding areas. Birds at these remote places are, however, often not counted within standard monitoring programmes. As in the Osterems a new remote sandbank island, the Kachelotplate, is emerging, we initiated a pilot study based on aerial counts to evaluate the importance of this island as roost site for waterbirds in the context of the surrounding islands. To check for the representativeness of the aerial counts, we compared numbers (i) on one occasion with a synchronous ground survey, and (ii) all aerial counts with the long-term average for those areas regularly covered by ground counts. Numbers of birds in flocks counted during synchronous aerial and ground counts were in good agreement. Nevertheless, birds in structured areas and small waders were difficult to count from the air. In general, a calibration of aerial counts and long-term experience is necessary to obtain realistic results by counting waterbirds from an aeroplane. Waterbirds in the Osterems showed the typical seasonal phenology for the East-Frisian Wadden Sea. Given the size of the study area, bird numbers were relatively high. Besides the Kachelotplate, which was important for the Common Eider and gulls for roosting, another remote island, Lutje Horn, was of paramount importance as roost site, in particular for the Eurasian Oystercatcher, Eurasian Curlew, and in spring for terns. A clear distinction could be made between outer, open islands like the Kachelotplate, which were used by birds feeding on pelagic food sources, and sheltered areas, used by benthic foragers, supporting the idea that birds try to reduce travelling costs between feeding and roosting areas. Furthermore, the study underlined the importance of remote, undisturbed roosting areas for waterbirds in the Wadden Sea.

The timing of the start and duration of breeding and the effect of these on breeding productivity were analysed for African Black Oystercatchers Haematopus moquini on Robben Island, South Africa, over three breeding seasons from 2001 to 2004. African Black Oystercatchers have a long breeding season, from November to March, enabling a second or sometimes a third nesting attempt after depredation or a natural disaster that destroys nests. The incubation starting date was known or estimated for 205 African Black Oystercatcher clutches over three breeding seasons. Using the estimated starting date of incubation for each nest we found that the 2001/02 and 2002/03 breeding seasons started approximately two weeks earlier than the 2003/04 season and that the 2002/03 breeding season ended approximately one month later than the other two. The late start of the 2003/04 breeding season may be a consequence of greater predation compared to the previous two breeding seasons. The 2003/04 breeding season was the shortest...

Wetlands are critical foraging areas for many waterbird species, and their relatively high productivity often determines the coexistence of several species using food resources for breeding and/or refueling during migration. Between 18 October and 20 December 2000, we gathered information on foraging habitat use and feeding techniques of sixteen waterbirds during the austral spring at Malaspina inlet, Chubut, Argentina. We quantified the utilization by waterbirds of ten foraging habitat types and seven feeding techniques on seven fixed survey stations along the coastline, representing the different coastal habitats of the Malaspina inlet. The waterbird assemblage was structured in three main guilds: shallow water frequenters (three cormorants, two terns, a grebe, and two steamer-ducks), hard habitat peckers (two gulls, an egret, and an oystercatcher) and soft habitat frequenters (two oystercatchers, a sandpiper, and a duck). These differed greatly in their use of habitats and feeding techniques, ...

Population models show that the response of migratory bird populations to a reduction in the area, or change in the quality, of their winter feeding areas depends critically on the shape (linear or non-linear) and strength (slope) of the relationship describing how the proportion dying from starvation changes with population density. Yet the parameters that define such density-dependent functions are extremely difficult to estimate from direct measurements of mortality at different population sizes. Even if they could be estimated, there would be uncertainty as to whether or not the relationship would remain the same, and thus provide reliable predictions, in the new circumstances for which forecasts are required. This paper summarizes studies of the Oystercatcher Haematopus ostralegus which aim to derive the shape and strength of the winter density-dependent mortality and emigration function for one estuary, under existing and new circumstances, from the responses of individual birds to each other and to their spatially and seasonally varying food supply. Based on these studies, an individuals-based, physiologically structured game theoretic distribution model has been built which predicts the carrying capacity and numbers of birds dying at different population sizes. The model also can be applied to Oyster-catchers occupying several estuaries distributed throughout their wintering range and can thus be extended to the entire biogeographical or global population. In addition, it can be used to identify some easily measured behavioural and ecological parameters that identify those species, from a wide range of taxa, that are most likely to be affected by habitat loss and change.