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Many migratory bird species have undergone recent population declines, but there is considerable variation in trends between species and between populations employing different migratory routes. Understanding species‐specific migratory behaviours is therefore of critical importance for their conservation. The Common Sandpiper Actitis hypoleucos is an Afro‐Palaearctic migratory bird species whose European populations are in decline. We fitted geolocators to individuals breeding in England or wintering in Senegal to determine their migration routes and breeding or non‐breeding locations. We used these geolocator data in combination with previously published data from Scottish breeding birds to determine the distributions and migratory connectivity of breeding (English and Scottish) and wintering (Senegalese) populations of the Common Sandpiper, and used simulated random migrations to investigate wind assistance during autumn and spring migration. We revealed that the Common Sandpipers tagged in England spent the winter in West Africa, and that at least some birds wintering in Senegal bred in Scandinavia; this provides insights into the links between European breeding populations and their wintering grounds. Furthermore, birds tagged in England, Scotland and Senegal overlapped considerably in their migration routes and wintering locations, meaning that local breeding populations could be buffered against habitat change, but susceptible to large‐scale environmental changes. These findings also suggest that contrasting population trends in England and Scotland are unlikely to be the result of population‐specific migration routes and wintering regions. Finally, we found that birds used wind to facilitate their migration in autumn, but less so in spring, when the wind costs associated with their migrations were higher than expected at random. This was despite the wind costs of simulated migrations being significantly lower in spring than in autumn. Indeed, theory suggests that individuals are under greater time pressures in spring than in autumn because of the time constraints associated with reproduction. [ABSTRACT FROM AUTHOR]

Yearly electricity production has increased steadily worlwide in recent decades and the associated overhead power lines are widespread and occur across urban and natural habitats, and often in remote areas where there is little other anthropogenic influence. Here we assessed the effects of overhead power lines on the density of ground‐nesting birds in the Icelandic lowlands, which host several populations of international importance. The combined breeding density of the eight study species increased significantly from ~ 112 birds/km2 close (< 50 m) to the power lines to ~ 177 birds/km2 away (450–500 m) from the power lines, with two of these species (Eurasian Whimbrel Numenius phaeopus and Common Redshank Tringa totanus) increasing significantly with distance from power lines and six species (European Golden Plover Pluvialis apricaria, Common Snipe Gallinago gallinago, Meadow Pipit Anthus pratensis, Black‐tailed Godwit Limosa limosa, Dunlin Calidris alpina and Redwing Turdus iliacus) showing no changes. These findings suggest that power lines can influence the breeding density of ground‐nesting bird species in their vicinity and that accounting for such effects when planning future infrastructure will be imperative. [ABSTRACT FROM AUTHOR]

Colonization of islands by long‐distance dispersers has great impact on genetic diversification among populations and may spearhead speciation events. We investigated intra‐ and interspecific divergence in Charadrius plovers with populations on mainland Africa, Madagascar and St Helena. We analysed microsatellite loci and sequence data from four nuclear and two mitochondrial gene regions. Charadrius plovers are shorebirds with high dispersal and mobility. Our results confirmed genetic differentiation between Madagascar and mainland populations of three plover species (White‐fronted Plover Charadrius marginatus, Kittlitz's Plover Charadrius pecuarius and, based on sequence data only, Three‐banded Plover Charadrius tricollaris) but highlight substantial variation in levels of intraspecific divergence among the three species. Namely, the Kittlitz's Plover, a dispersive habitat generalist with a polygamous mating system, exhibited lower island–mainland differentiation (0.05% COI sequence divergence) compared with the two monogamous species, the White‐fronted Plover (0.6% COI divergence) and Three‐banded Plover (1.6% COI divergence). In addition, past colonization of the islands of St Helena and Madagascar by ancestors of today's Kittlitz's Plover has led to the evolution of two endemic island species, the Madagascar Plover Charadrius thoracicus and the more closely‐related St Helena Plover Charadrius sanctaehelenae. We discuss the factors driving species differences in island–mainland divergence and highlight the importance of conserving genetically unique island populations and island habitats to safeguard future evolutionary potential. [ABSTRACT FROM AUTHOR]

Changes in demographic rates underpin changes in population size, and understanding demographic rates can greatly aid the design and development of strategies to maintain populations in the face of environmental changes. However, acquiring estimates of demographic parameters at relevant spatial scales is difficult. Measures of annual survival rates can be particularly challenging to obtain because large‐scale, long‐term tracking of individuals is difficult and the resulting data contain many inherent biases. In recent years, advances in both tracking and analytical techniques have meant that, for some taxonomic groups, sufficient numbers of survival estimates are available to allow variation within and among species to be explored. Here we review published estimates of annual adult survival rates in shorebird species across the globe, and construct models to explore the phylogenetic, geographical, seasonal and sex‐based variation in survival rates. Models of 295 survival estimates from 56 species show that survival rates calculated from recoveries of dead individuals or from return rates of marked individuals are significantly lower than estimates from mark–recapture models. Survival rates also vary across flyways, largely as a consequence of differences in the genera that have been studied and the analytical methods used, with published estimates from the Americas and from smaller shorebirds (Actitis, Calidris and Charadrius spp.) tending to be underestimated. By incorporating the analytical method used to generate each estimate within a mixed model framework, we provide method‐corrected species‐specific and genus‐specific adult annual survival estimates for 52 species of 15 genera. [ABSTRACT FROM AUTHOR]

The Arctic is experiencing rapidly warming conditions, increasing predator abundance, and diminishing population cycles of keystone species such as lemmings. However, it is still not known how many Arctic animals will respond to a changing climate with altered trophic interactions. We studied clutch size, incubation duration and nest survival of 17 taxa of Arctic‐breeding shorebirds at 16 field sites over 7 years. We predicted that physiological benefits of higher temperatures and earlier snowmelt would increase reproductive effort and nest survival, and we expected increasing predator abundance and decreasing abundance of alternative prey (arvicoline rodents) to have a negative effect on reproduction. Although we observed wide ranges of conditions during our study, we found no effects of covariates on reproductive traits in 12 of 17 taxa. In the remaining taxa, most relationships agreed with our predictions. Earlier snowmelt increased the probability of laying a full clutch from 0.61 to 0.91 for Western Sandpipers, and shortened incubation by 1.42 days for arcticola Dunlin and 0.77 days for Red Phalaropes. Higher temperatures increased the probability of a full clutch from 0.60 to 0.93 for Western Sandpipers and from 0.76 to 0.97 for Red‐necked Phalaropes, and increased daily nest survival rates from 0.9634 to 0.9890 for Semipalmated Sandpipers and 0.9546 to 0.9880 for Western Sandpipers. Higher abundance of predators (foxes) reduced daily nest survival rates only in Western Sandpipers (0.9821–0.9031). In contrast to our predictions, the probability of a full clutch was lowest (0.83) for Semipalmated Sandpipers at moderate abundance of alternative prey, rather than low abundance (0.90). Our findings suggest that in the short‐term, climate warming may have neutral or positive effects on the nesting cycle of most Arctic‐breeding shorebirds. [ABSTRACT FROM AUTHOR]

Sexual size dimorphism ( SSD) is common in birds and has been linked to various selective forces. Nevertheless, the question of how and when the sexes start to differentiate from each other is poorly studied. This is a critical knowledge gap, as sex differences in growth may cause different responses to similar ecological conditions. In this study, we describe the sex-specific growth - based on body mass and five morphometric measurements - of 56 captive Black-tailed Godwit Limosa limosa limosa chicks raised under ad libitum food conditions, and conclude that all six growth curves are sex-specific. Females are the larger sex in terms of body mass and skeletal body size. To test whether sex-specific growth leads to sex-specific susceptibility to environmental conditions, we compared the age-specific sizes of male and female chicks in the wild with those of Black-tailed Godwits reared in captivity. We then tested for a relationship between residual growth and relative hatching date, age, sex and habitat type in which the wild chicks were born. Early-hatched chicks were relatively bigger and in better condition than late-hatched chicks, but body condition and size were not affected by natal habitat type. Female chicks deviated more negatively from the sex-specific growth curves than male chicks for body mass and total-head length. This suggests that the growth of the larger females is more susceptible to limiting environmental conditions. On average, the deviations of wild chicks from the predicted growth curves were negative for all measurements, which suggests that conditions are limiting in the current agricultural landscape. We argue that in estimating growth curves for sexually dimorphic species, it is critical first to make accurate sex and age determinations. [ABSTRACT FROM AUTHOR]

Key demographic parameters often show substantial annual variation that can have important consequences for rates of population growth. Since 2011 we have conducted annual estimates of the productivity of Icelandic Black-tailed Godwits Limosa limosa islandica over a large part of their breeding range. During this period, a volcanic eruption resulted in extensive dust deposition across the region. We show that Godwit productivity varies with spring temperatures but in the year of the volcanic eruption, productivity was reduced to almost zero. This rare but extreme event is likely to have had only a short-term influence, whereas ongoing warming of sub-Arctic regions is potentially a more substantial driver of the continued growth of this population. [ABSTRACT FROM AUTHOR]

Trans-equatorial avian migrants tend to breed, moult and migrate - the main energy-requiring events in their lifecycle - at different times. Little is known about the relationship between wing moult and pre-migratory fuelling in waders on their non-breeding grounds, where time is less constrained than during their brief high-latitude breeding season. We determined age-related strategies of Wood Sandpipers Tringa glareola to balance the energetic demands of primary moult against pre-migratory fuelling in southern Africa by analysing body mass and primary moult at first capture of 1721 birds mist-netted in 1972-96 at waterbodies in Zimbabwe. Adults moulted all their primaries in August-December, but immatures underwent a supplemental moult of varying numbers of outer primaries in December-April, close to departure. We used locally weighted linear regression to estimate trends in Wood Sandpiper body mass from 1 July to 1 May. They maintained low mass from arrival in July-September to February-early March. Adults fuelled from 10 February to 1 May at a mean rate of 0.25 g/day (sd = 0.16). Most adults (98%) began fuelling 10-75 days after completing primary moult. Immatures fuelled from 4 March to 13 April at 0.24 g/day (sd = 0.14). They used varying strategies depending on their condition: a brief gap between moult and fuelling; an overlap of these processes near departure, leading to slower fuelling; or skipping fuelling altogether and staying in southern Africa for a 'gap year'. Immatures moulting three or five outer primaries fuelled more slowly than post-moult birds. Immatures moulting four outer primaries started fuelling 3 weeks later but at a higher rate than did post-moult birds of this group. In post-moult immatures, the later they ended moult, the later and faster they fuelled. The heaviest adults and immatures using all moult patterns accumulated fuel loads of c. 50% of lean body mass, and could potentially cross 2397-4490 km to reach the Great Rift Valley in one non-stop flight. Immatures were more flexible in the timing and extent of moult and in the timing and rate of fuelling than adults. This flexibility enables inexperienced Wood Sandpipers to cope with inter-annual differences in feeding conditions at Africa's ephemeral inland waterbodies. [ABSTRACT FROM AUTHOR]

Sexual size dimorphism ( SSD) among adults is commonly observed in animals and is considered to be adaptive. However, the ontogenic emergence of SSD, i.e. the timing of divergence in body size between males and females, has only recently received attention. It is widely acknowledged that the ontogeny of SSD may differ between species, but it remains unclear how variable the ontogeny of SSD is within species. Kentish Plovers Charadrius alexandrinus and Snowy Plovers C. nivosus are closely related wader species that exhibit similar, moderate ( c. 4%), male-biased adult SSD. To assess when SSD emerges we recorded tarsus length variation among 759 offspring in four populations of these species. Tarsus length of chicks was measured on the day of hatching and up to three times on recapture before fledging. In one population (Mexico, Snowy Plovers), males and females differed in size from the day of hatching, whereas growth rates differed between the sexes in two populations (Turkey and United Arab Emirates, both Kentish Plovers). In contrast, a fourth population (Cape Verde, Kentish Plovers) showed no significant SSD in juveniles. Our results suggest that adult SSD can emerge at different stages of development (prenatal, postnatal and post-juvenile) in different populations of the same species. We discuss the proximate mechanisms that may underlie these developmental differences. [ABSTRACT FROM AUTHOR]

The Common Redshank Tringa totanus breeding population on British saltmarshes has declined by over 50% since 1985, with declines linked to changes in grazing management. Conservation initiatives have encouraged low-intensity grazing of less than one cattle per hectare, but Redshank have continued to decline, even in regions where light grazing was predominant. This study quantified effects of grazing intensity on Redshank nest survival over six lightly grazed saltmarshes with livestock densities between 0 and 0.82 cattle per hectare, in the Ribble Estuary, northwest England. We assessed whether grazing resulted in nest mortality directly through cattle trampling and/or indirectly through grazer modification of habitat that accelerates predation risks. Cattle density was recorded both during the Redshank breeding season and for 1 year prior to the study, to account for both short-term trampling effects and the longer term effects on vegetation. Results showed that risk of nest loss to trampling increased from 16% at 0.15 cattle per hectare to 98% at 0.82 cattle per hectare in the breeding season. The risk of a nest being predated increased from 28% with no grazing to 95% at 0.55 cattle per hectare based on all year grazing data. These results suggest that even light conservation grazing at less than one cattle per hectare can reduce Redshank nest survival rates to near zero. It may therefore be appropriate to reduce saltmarsh grazing intensities, or change the timing of saltmarsh grazing to reduce the number of livestock present during the Redshank breeding season. [ABSTRACT FROM AUTHOR]

We investigated the effects of body mass and latitude on primary moult duration from published data of migrating shorebirds that moult exclusively on the wintering grounds. Non-phylogenetic and phylogenetic models demonstrated that body mass and latitude correlate with moult duration in a non-additive way: the models predict different latitudinal relationships for smaller and larger shorebirds, and in the northern hemisphere, primary moult duration increased allometrically with body mass (exponent = 0.17), whereas in the southern hemisphere, primary moult duration was not correlated with body mass. If birds optimize feather quality and if slower moult yields sturdier feathers, the fast primary moult of northerly wintering shorebirds indicates additional selection pressures at work. [ABSTRACT FROM AUTHOR]

We review the conservation issues facing migratory shorebird populations that breed in temperate regions and use wetlands in the non-breeding season. Shorebirds are excellent model organisms for understanding ecological, behavioural and evolutionary processes and are often used as indicators of wetland health. A global team of experienced shorebird researchers identified 45 issues facing these shorebird populations, and divided them into three categories (natural, current anthropogenic and future issues). The natural issues included megatsunamis, volcanoes and regional climate changes, while current anthropogenic threats encompassed agricultural intensification, conversion of tidal flats and coastal wetlands by human infrastructure developments and eutrophication of coastal systems. Possible future threats to shorebirds include microplastics, new means of recreation and infectious diseases. We suggest that this review process be broadened to other taxa to aid the identification and ranking of current and future conservation actions. [ABSTRACT FROM AUTHOR]

Agricultural intensification is one of the main drivers of farmland bird declines, but effects on birds may be confounded with those of climate change. Here we examine the effects of intensification and climate change on a grassland breeding wader, the Black-tailed Godwit Limosa l. limosa, in the Netherlands. Population decline has been linked to poor chick survival which, in turn, has been linked to available foraging habitat. Foraging habitat of the nidifugous chicks consists of uncut grasslands that provide cover and arthropod prey. Conservation measures such as agri-environment schemes aim to increase the availability of chick foraging habitat but have not yet been successful in halting the decline. Field observations show that since the early 1980s, farmers advanced their first seasonal mowing or grazing date by 15 days, whereas Godwits did not advance their hatching date. Ringing data indicate that between 1945 and 1975 hatching dates advanced by about 2 weeks in parallel with the advancement of median mowing dates. Surprisingly, temperature sums at median mowing and hatching dates suggest that while the agricultural advancement before 1980 was largely due to agricultural intensification, after 1980 it was largely due to climate change. Examining arthropod abundance in a range of differently managed grasslands revealed that chick food abundance was little affected but that food accessibility in intensively used tall swards may be problematic for chicks. Our results suggest that, compared with 25 years ago, nowadays (1) a much higher proportion of clutches and chicks are exposed to agricultural activities, (2) there is little foraging habitat left when chicks hatch and (3) because of climate change, the vegetation in the remaining foraging habitat is taller and denser and therefore of lower quality. This indicates that for agri-environment schemes to make a difference, they should not only be implemented in a larger percentage of the breeding area than the current maxima of 20–30% but they should also include measures that create more open, accessible swards. [ABSTRACT FROM AUTHOR]

Two phases of an experimental reduction in management at Langholm Moor in southwest Scotland provided an insight into factors that determined trends in the abundance of moorland birds. In 1992 the historical control of breeding Hen Harriers Circus cyaneus stopped and in 2000 grouse moor management was discontinued. Golden Plover Pluvialis apricaria, Lapwing Vanellus vanellus, Curlew Numenius arquata and Red Grouse Lagopus lagopus scoticus declined, whilst Carrion Crow Corvus corone and Snipe Gallinago gallinago increased. Hen Harriers increased from two to 20 breeding females, then declined back to two. Lapwing abundance was positively associated with that of Hen Harriers, and moorland passerines (Skylark Alauda arvensis, Meadow Pipit Anthus pratensis and Stonechat Saxicola torquata) were negatively associated. Golden Plover, Lapwing, Curlew, Red Grouse, Skylark and Hen Harrier were more abundant when the moor was managed for grouse, whilst Carrion Crow, a common predator of clutches of ground-nesting birds, increased during the second half when management ceased. Increased Crow numbers, together with an increase in Red Foxes Vulpes vulpes, probably contributed to the observed bird declines. [ABSTRACT FROM AUTHOR]