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Some populations of common terns (Sterna hirundo) breeding at inland lakes in North America are declining, including the Laurentian Great Lakes. Terns nesting at inland colonies forage in freshwater during the breeding season and primarily in coastal marine environments during the nonbreeding season. As piscivores, they are susceptible to dietary Hg exposure. To characterize patterns of Hg exposure in this population, we 1) quantified within and among season differences in total mercury (THg) concentrations (μg/g) in blood and feathers at 2 Lake Superior breeding colonies, and 2) documented spatial and temporal variation in exposure by studying adult foraging ecology using geospatial tracking devices and stable isotopes. We used general linear models to assess the relationship between isotopic composition and THg concentrations in bird tissues relative to sex, age, colony location, and season. The THg concentrations were lowest in winter-grown feathers (geometric mean [95% confidence limits]): 1.32 (1.09-1.59) μg/g dw (n = 60), higher at the more industrially influenced colony (chick feathers: 4.95 [4.62-5.37] μg/g dw [n = 20]), and increased with a riverine-based diet. During the breeding season, Hg exposure varied along a gradient from lake to river, with adult females having lower blood THg concentrations than males (females: 0.83 [0.67-1.03]) μg/g ww (n = 7); males: 1.15 (0.92-1.45) μg/g ww (n = 5). Stable isotope values suggested adults obtained 42 ± 12% (n = 12) of their diet from the river during incubation, which was validated with tracking data. During chick-rearing, chicks obtained 68 ± 19% (n = 44) of their diet from the river. Our results indicate colony location, foraging behavior, and season influenced Hg exposure for these Lake Superior colonies and underscores the importance of local contamination with respect to exposure. Integr Environ Assess Manag 2021;17:398-410. © 2020 SETAC.

The impact of habitat loss on shorebirds may be exacerbated by disturbance from human recreational use, which further reduces the amount of coastal habitat that is functionally available. This can have consequences for the condition of individual birds or for population processes, both of which should be considered in strategies to reduce conflict between shorebirds and recreational users of coastal habitat. Our objectives were to determine the associations between human recreational use, coastal habitat modifications, and Piping Plover (Charadrius melodus) body condition and demography. We monitored banded Piping Plovers throughout their annual cycle to assess variation in body condition, true survival, and site fidelity related to disturbance regimes in 8 geographically proximate, nonbreeding areas along the southeastern Atlantic Coast of North America from 2012 to 2016. Piping Plovers in disturbed sites were 7% lighter than those in less disturbed sites. Additionally, true annual survival was ...

Common Terns (Sterna hirundo) breeding at inland lakes in North America have experienced significant population declines since the 1960s. Although management actions aimed at mitigating effects of habitat loss and predation have been largely effective, numbers continue to decline, which suggests that the population may be limited during the nonbreeding season. Between 2013 and 2015, we used light-level geolocators to track Common Terns nesting at 5 inland colonies—from Lake Winnipeg in Manitoba, Canada, to the eastern Great Lakes region of the United States and Canada—to identify migratory routes and stopover and wintering sites and to determine the strength of migratory connectivity among colonies. Within 46 recovered tracks, we found evidence of a longitudinal gradient in use of migration routes and stopover sites among colonies and identified major staging areas in the lower Great Lakes and at inland and coastal locations along the Atlantic coast, Florida, and the Gulf of Mexico. Low migratory connectivity across inland colonies illustrates high intermixing within wintering sites, with many birds spending the nonbreeding season in Peru (70%) and the remainder spread throughout the Gulf of Mexico, Central America, and northwestern South America. While the large spatial spread and intermixing of individuals during the nonbreeding season may buffer local effects of climate change and human disturbance, the aggregation of individuals along the coast of Peru could make them vulnerable to events or changes within this region, such as increased frequency and intensity of storms in the Pacific, that are predicted to negatively influence breeding productivity and survival of Common Terns. Identifying sources of mortality during the nonbreeding season, quantifying winter site fidelity, and reinforcing the importance of continued management of inland breeding colonies are vital priorities for effective conservation and management of this vulnerable population.

Habitat selection occurs at multiple spatial scales and affects demographic processes including reproductive success. Few studies, however, have linked multi-scale habitat selection to reproductive success. We investigated breeding habitat selection at three spatial scales (nest site, nest area and territory), and the consequences of habitat selection on reproductive success of four riverine sandbar-nesting bird species in Cambodia. All species generally selected larger habitat patches, in territories with higher proportions of bare ground substrates, including gravel and dry mud. Individuals generally selected areas with less vegetation; however, at smaller spatial scales, Small Pratincoles (Glareola lactea) and Little Ringed Plovers (Charadrius dubius) used sites with more vegetation. Vegetation generally had a negative effect on reproductive success. For River Terns (Sterna aurantia), nest success was lower in areas with a higher proportion of invasive Mimosa pigra, and chick survival decreased with vegetation height. River Lapwing (Vanellus duvaucelii) nest success decreased with more woody stems, and nest success of Small Pratincoles and Little Ringed Plovers decreased with more herbaceous vegetation. Negative effects of vegetation were likely due to reduced ability of incubating birds to detect predators, or increased cover or foraging efficiency of predators. Finally, proximity to the river channel reduced nest success; nests near the channel had a higher risk of flooding. This is the first study to identify variables associated with habitat selection for all species in this study and to relate habitat use to reproductive success. Results of this study will aid conservation efforts for these regionally threatened species.

Effective conservation for listed migratory species requires an understanding of how drivers of population decline vary spatially and temporally, as well as knowledge of range-wide connectivity between breeding and nonbreeding areas. Environmental conditions distant from breeding areas can have lasting effects on the demography of migratory species, yet these consequences are often the least understood. Our objectives were to 1) evaluate associations between survival and extreme environmental disturbances at nonbreeding areas, including hurricanes, harmful algal blooms, and oil spills, and 2) estimate migratory connectivity between breeding and nonbreeding areas of midcontinental piping plovers (Charadrius melodus). We used capture and resighting data from 5067 individuals collected between 2002 and 2019 from breeding areas across the midcontinent, and nonbreeding areas throughout the Gulf of Mexico and southern Atlantic coasts of North America. We developed a hidden Markov multistate model to estimate seasonal survival and account for unobservable geographic locations. Hurricanes and harmful algal blooms were negatively associated with nonbreeding season survival, but we did not detect a similarly negative relationship with oil spills. Our results indicated that individuals from separate breeding areas mixed across nonbreeding areas with low migratory connectivity. Mixing among individuals in the nonbreeding season may provide a buffering effect against impacts of extreme events on any one breeding region. Our results suggest that understanding migratory connectivity and linking seasonal threats to population dynamics can better inform conservation strategies for migratory shorebirds.

Novel monitoring and management techniques may be required when working with colonial waterbirds nesting on anthropogenic sites. We tested the utility of fixed sampling frames (quadrats) for estimating number of common tern ( Sterna hirundo ) nests and colony dynamics at a site in northern Lake Huron, U.S.A. We also examined whether within-season herbaceous vegetation management affected number of nests. We were unable to detect any avoidance of fixed quadrats (N = 15) versus staked quadrats (N = 15) over 10 count days in 2015 (Mann-Whitney, P ≥ 0.16). Both distance from human disturbance (m) and Julian day were significant ( P P ≥ 0.18). For common terns, and potentially other colonial waterbirds breeding on anthropogenic sites in the Great Lakes, we conclude that a fixed quadrat methodology may provide a useful way of estimating colony size and colony dynamics. Future studies should be conducted to compare our novel method with more traditional monitoring techniques.

Medium-distance migrant shorebirds that nest on beaches contend with human disturbance and habitat development on their breeding, migratory stopover and non-breeding sites. Conservation has focused on breeding areas because protection of nests is more tractable than protection of non-breeding habitat. As breeding ground management has encountered diminishing returns, interest in understanding threats in non-breeding areas has increased. However, robust estimates of non-breeding demographic rates (such as entry and persistence probabilities) and abundance are generally lacking, hindering the study of limiting or regulating factors. Estimating such rates is made more difficult by complex population dynamics at non-breeding sites. In the important non-breeding site of South Carolina, endangered Piping Plovers Charadrius melodus start arriving in July and some depart prior to December (the autumn-only population) while others remain through March (the wintering population, which in other locales has been shown to be closed in the winter months of December to February) or even until May. State uncertainty capture-mark-recapture models provide a means for estimating entry and persistence rates for such co-occurring populations. We estimated the proportion of the population entering the study area per survey (entry probability) and proportion remaining per survey (persistence rate) for both populations during the autumn, and abundance of the wintering population in the winter months, at four high-use sites in South Carolina in the non-breeding periods of 2006/7 and 2007/8, taking advantage of birds previously colour-ringed on the breeding grounds. We were able to make fairly precise estimates of entry and persistence rates with small sample sizes. Cumulative probability of entry was ~50% by the end of July and reached 95% for both populations by October. Estimated stopover duration for birds in the autumn-only population was 35 days in year 1 and 42 days in year 2. In the winter months (December to January), we estimated a wintering super-population size ± SE of 71±16 Piping Plovers in the first year and 75±16 Piping Plovers in the second year. If ringing programs on the breeding grounds continue, annual standardized resighting surveys in the nonbreeding period and mark-recapture models can provide robust estimates of entry and persistence rates and abundance. Long term monitoring programs can thus permit separation of demographic variance from sampling error, which is crucial for further research into population regulation and limiting factors. Our results suggest that habitat protection intended to benefit non-breeding Piping Plovers at our coastal sites should be in effect by late summer, as many birds are resident from July through the end of winter in March. This article is protected by copyright. All rights reserved.

Breeding colonies of black terns (Chlidonias niger) have become increasingly rare in U.S. Great Lakes coastal wetlands since the mid-twentieth century, with an almost 90% decline in the number of active colony sites since 1991. Although the specific causes of this wetland species’ decline are unknown, habitat loss and degradation are thought to be a major barrier to conservation. Using data from the Great Lakes Colonial Waterbird Survey, we took a unique regional and historical approach to investigate the relationship between black tern colony site abandonment and a suite of local and landscape-scale habitat features in U.S. Great Lakes coastal wetlands. We employed logistic regression models and a combination of stepwise selection procedures to identify the best predictive model for black tern colony abandonment. According to the selected model, breeding colonies with fewer nests were more likely to be abandoned over the following decadal observation period than breeding colonies with more nests. Colony sites were also more likely to be abandoned when vegetation within the wetland shifted towards larger, denser clusters. We performed a simulation study that showed that failing to account for association between observations from the same site affected model selection results, but that cross-validation error for the selected model remained low unless site effects were very strong. Results of this study suggest that focus on protection of sites harboring large numbers of black terns and vegetation management will help limit further colony abandonments.

SummaryDirect payments to communities or individuals have gained traction as a tool for species conservation; however, few studies have evaluated their effectiveness. From 2010 to 2014, we monitored nests and implemented a direct payment nest protection programme for six sandbar-nesting bird species on the Mekong River, Cambodia, and tested if nest protection improved reproductive success. Nests were guarded by community members; additionally, exclosures were used to protect nests of River Tern Sterna aurantia, the species of highest conservation concern. We investigated factors affecting nest and chick survival, and probability of nest failure due to egg harvest or predation. Nesting later in the season generally resulted in lower nest and chick survival. Nest protection improved survival rates of River Tern nests and chicks, and Small Pratincole Glareola lactea nests. River Tern nest success was 60% for exclosed (and guarded) nests, 29% for guarded (but unexclosed) nests, and 5% for unprotected nests. River Tern fledging success was 82% for exclosed chicks, 40% for chicks that were guarded only, and 2% for unprotected chicks. Small Pratincole nest success was 21% for guarded and 6% for unguarded nests. Egg harvest by humans was lower among protected nests and declined during the study. Nest predation by animals increased during the study despite nest guarding; however, predator exclosures effectively protected nests and chicks. Additional predator control measures could further improve reproductive success of sandbar-nesting birds. Overall, nest protection involving direct payments was highly effective, but required diligent use of nest exclosures, frequent monitoring, and strong community relationships.

Remotely sensed land cover data enable characterization of avian habitat over large spatial scales, which can be applied to regional conservation planning. Black Terns (Chlidonias niger) have been declining in the U.S. Great Lakes region for decades. Although causes of the decline are not well understood, habitat loss and degradation are viewed as major barriers to recovery. The Upper Mississippi River and Great Lakes Region Joint Venture, a partnership for bird conservation in the Upper Midwest, developed a landscape suitability index for the wetland-breeding Black Tern based on remotely sensed land cover to choose habitat to enhance or restore. We tested the validity of this index and compared it to an alternative index we constructed from results of field surveys. Over 2 breeding seasons, we surveyed for presence of Black Tern breeding colonies in 158 wetlands across the Great Lakes region and compared our findings with predictions of the existing index. We used our first season of surveys, nu...

Recent dramatic growth of the North American Interior population of Double-crested Cormorants (Phalacrocorax auritus) has led to concern about potential impacts of this species on co-nesting colonial waterbirds. Previous investigations of these concerns have focused on Double-crested Cormorant interactions with other species within homogeneous breeding environments, making broad patterns difficult to identify. The present study examined how nest location, nest density, and species identity mediate agonistic interactions among Double-crested Cormorants and Great Blue Herons (Ardea herodias) nesting at a colony site in central Minnesota, USA. Twenty-six Double-crested Cormorant nests and 27 Great Blue Heron nests were observed for 30 min weekly for 8 weeks during the breeding season to estimate frequency of agonistic behavior and identify species-level patterns of interaction. Most agonistic interactions observed (81%) were intraspecific interactions among Double-crested Cormorants; Great Blue Her...

Few investigators have studied the offspring sex ratios of monomorphic shorebirds because visually determining the sex of juveniles is not possible. We investigated the ontogeny of an observed male-biased adult sex ratio in the federally endangered Great Lakes population of Piping Plovers (Charadrius melodus). We determined sex ratios at hatching, banding ( = 9.0 d old), and fledging (23 d old) to determine if the bias arises during the pre-fledging period and, if so, at what stage. For three consecutive years (2012–2014), we used a molecular technique to determine the sex of 307 chicks and followed individuals to a stage where survival to fledging could be inferred. Within fully-sexed broods at hatching, the average proportions of male chicks (2012–2014) were 0.47, 0.58, and 0.54, respectively. At banding, the sex ratio remained unbiased in 2012 (0.51), but was male-biased in 2013 (0.59) and 2014 (0.57). Overall, the sex ratio did not differ significantly from parity at fledging in 2012, but did differ during 2013 (P = 0.01) and 2014 (P = 0.03). Using logistic regression models fit using Bayesian inference, we found strong support for a sex effect on chick survival to fledging age, with higher male than female survival (μmale = 0.83 [95% credible interval: 0.75–0.90]; μfemale = 0.71 [0.61–0.80]). These results suggest that the male-biased adult sex ratio in Piping Plovers arises, in part, due to differential survival during the pre-fledging period. This difference did not result from female chicks hatching later in the season or weighing less at banding than male chicks, factors that could potentially affect the likelihood of survival. Future investigations into possible behavioral- or weather-related influences on sex-specific survival are needed. Our results have important implications for (1) identifying management efforts needed to increase recruitment given female-biased chick mortality, and (2) conducting population viability analyses, which frequently assume an unbiased fledgling sex ratio. RESUMEN La mortalidad de pichones conduce a tasa de sexos sesgada hacia los machos en el amenazada Chorlo chiflador Pocos investigadores han estudiado la tasa de sexos de las cria de aves marinas monomorficas debido a que la determinacion visual del sexo de los juveniles no es posible. Investigamos la ontogenia en la poblacion con estatus Amenazada a nivel Federal de los Grandes Lagos del Chorlo chiflador (Charadrius melodus) que presenta una tasa se sexos sesgada hacia los machos en adultos. Determinamos la tasa de sexos al nacer, al momento de anillarlos ( = 9.0 dias de edad), y cuando son volantones (23 dia de edad) para determinar si el sesgo surge durante el periodo pre-volanton y, si es asi, en que estadio. Durante tres anos consecutivos (2012–2014), utilizamos una tecnica molecular para determinar el sexo de 307 pichones y seguimos a los individuos a un estadio donde la superviviencia a volanton podia ser inferida. Dentro de cada nidada completamente sexada al nacer, la proporcion relativa de pichones macho (2012–2014) fue de 0.47, 0.58, y 0.54, respectivamente. Al momento del anillado, la tasa de sexos permanecio sin sesgo en 2012 (0.51), pero se encontro sesgada hacia los machos en 2013 (0.59) y 2014 (0.57). En general, la tasa de sexos no difirio significativamente de la igualdad en los volantones en 2012, pero si difirio durante el 2013 (P = 0.01) y el 2014 (P = 0.03). Usando modelos de ajuste a regresion logistica usando inferencia bayesiana, encontramos fuerte soporte para un efecto del sexo en la superviviencia de los pichones hacia la edad de volanton, siendo mas alta la superviviencia de machos que de hembras (μmachos = 0.83 [95% intervalo de credibilidad: 0.75–0.90]; μhembras = 0.71 [0.61–0.80]). Estos resultados sugieren que el sesgo en la tasa de sexos hacia los machos en el Chorlo chiflador surge, en parte, debido a una superviviencia diferencial durante el periodo pre-volanton. Estas diferencias no se debieron a que las hembras nacieran mas tarde en la temporada o a que pesaran menos que los machos durante el anillado, factores que podrian potencialmente afectar la probabilidad de la superviviencia. Futuras investigaciones sobre las posibles influencias comportamentales o dependientes del clima en la superviviencia sexo-especifica son necesarias. Nuestros resultados tienen importantes implicancias para (1) identificar esfuerzos de manejo necesarios a fin de incrementar el reclutamiento dada la mortalidad sesgada hacia las hembras de los pichones, y (2) llevar a cabo analisis de viabilidad poblacional, que frecuentemente asumen una tasa de sexos sin sesgo.

Adaptation depends on the additive genetic variance for fitness and its component traits. Yet estimating additive genetic variance and heritability for wild populations is challenging because determining relatedness of individuals is difficult. We used 20 years (1994–2013) of phenotypic records from mark-recapture data and a multi-generational pedigree to estimate quantitative genetic variation in three fitness-related traits in Great Lakes piping plovers (Charadrius melodus), an endangered wild shorebird. Genetic and environmental components of variance as well as heritabilities were estimated using Bayesian inference for animal models. Phenotypic variation in age-corrected chick mass was composed of a significant additive genetic component (h2 = 0.27; 95% credible interval: 0.16–0.38), and hatch year, common maternal environment, and hatch site effects. Conversely, natal dispersal distance and female breeding time were not significantly heritable (h2 = 0.03; 95% CI: 0.0–0.11; h2 = 0.08, 95% CI: 0.0–0.22, respectively). Rather, environmental factors (e.g., breeding site) are the main sources of variation in these two traits. Variation in female breeding time was minimally influenced by her mate and was moderately repeatable. The low potential for natal dispersal and breeding time to evolve may limit the ability of this population to adapt to climate change long-term. However, trait alteration could occur by a phenotypically plastic response, allowing rapid adjustment to novel environmental conditions and short-term persistence. Depending on the relative contribution of genetic and environmental influences on the trait(s) of interest, results from quantitative genetic studies can also help identify management priorities for endangered populations.

Renesting is an important breeding strategy used by birds to compensate for nest failure. If birds renest, clutch removal for captive rearing can be used to augment endangered populations; however, not all individuals renest following nest loss, and later nesting attempts may have lower survival rates and clutch sizes. We investigated variation in nest initiation date, clutch size, daily nest survival, renesting propensity, and renesting intervals of federally endangered Great Lakes Piping Plovers (Charadrius melodus) from 1993 to 2010. We also compared productivity under hypothetical clutch removal for captive rearing vs. non-removal scenarios. Nest initiation date was earlier for older adults and was more strongly affected by female than male age. Clutch size and nest survival decreased with later nest initiation, and nest survival increased with male age and nest age until close to hatching. Overall, Piping Plovers replaced 49% of failed nests. Renesting propensity decreased with later date, i...

Juvenile survival and age at first breeding (i.e. recruitment) are critical parameters affecting population dynamics in birds, but high levels of natal dispersal preclude measurement of these variables in most species. We used multi-state capture–recapture models to measure age-specific survival and recruitment probabilities of piping plovers Charadrius melodus in the Great Lakes region during 1993–2012. This federally endangered population is thoroughly monitored throughout its entire breeding range, minimizing concerns that measures of survival and recruitment are confounded by temporary or permanent emigration. First-year survival (± SE) averaged 0.284 ± 0.019 from mean banding age (9 d) and 0.374 ± 0.023 from fledging age (23 d). Factors that increased first-year survival during the pre-fledging period (9–23 d) included earlier hatching dates, older age at banding, greater number of fledglings at a given site, and better body condition at time of banding. However, when chicks that died prior to fledging were excluded from analysis, only earlier hatching dates improved first-year survival estimates. Females had a higher probability (0.557 ± 0.066) of initiating breeding at age one than did males (0.353 ± 0.052), but virtually all plovers began breeding by age three. Adult survival was reduced by increased hurricane activity on the southeast U.S. Atlantic coast where Great Lakes piping plovers winter and by higher populations of merlins Falco columbarius. Mean annual adult survival declined from 1993 to 2012, and did not differ between males and females. Enhanced body condition led to higher survival to fledge and early breeding led to improved first-year survival; therefore, management actions focused on ensuring access to quality feeding habitat for growing young and protecting early nests may increase recruitment in this federally endangered population.

Captive rearing of endangered species for later release is a method used to augment critically small populations, although studies have shown lower survival and fitness for individuals raised in captivity. Since 1992, recovery efforts for the endangered Great Lakes piping plover population have included captive rearing, but released young have lower survival than wild plover chicks. We tested the hypothesis that captive-reared chicks lack the ability to recognize predators by using visual and auditory stimuli. Vocalizations of predators and non-predators were combined with parental alarm calls, predator silhouettes, and a control to test for vigilant responses in captive-reared chicks prior to release. We tested for increases in average percent time spent on vigilant behaviors associated with exposure to predator and non-predator stimuli using linear mixed models. Chicks exhibited the greatest increase in vigilance when a treatment was combined with a parental alarm, regardless of whether the treatment was a predator or non-predator. Compared to white noise, average vigilance increased from 1.7% to 21.9% during non-predator treatments (95% CI: 8.0–34.2%) and to 78.3% during predator treatments (95% CI: 65.7–91.1%), indicating that chicks innately recognize avian predators as threatening. Average vigilance increased by 56.4% during predator treatments compared to non-predator treatments (95% CI: 49.8–64.8%), but individuals did not appear to differentiate between specific predators or non-predators. Our results provide strong evidence that captive-reared chicks innately recognize avian predators, which suggests that decreased post-release survival in captive-reared piping plovers is most likely caused by some other captivity-induced difference or by the lack of a parentally-taught behavior.

The Great Lakes population of Piping Plovers (Charadrius melodus) is federally endangered, numbering between 17 and 71 pairs during 1986–2011. Recovery efforts are diverse, but a major management focus is reduction of predation on eggs and chicks. We evaluated rates and potential causes of mortality for 2,143 chicks from 597 broods at 31 separate breeding sites during 1992–2011. Average daily survival rates of chicks increased from hatch until fledging (∼23 days of age), but this pattern exhibited substantial variation among breeding sites and years, so we included breeding sites and years as random effects in our models. Average (± SE) survival to fledging age was 0.556 ± 0.011. Survival increased with year (1992–2011) and declined with hatching date (28 May–25 July), with seasonal declines becoming more pronounced in recent years. Survival of chicks was reduced by heavy rain (>1 cm) during the first 3 days of life, but

Reproductive success commonly improves with age in birds. However, it is difficult to determine whether this phenomenon is due to breeding experience or other age-related factors because most potential explanatory factors are positively correlated. Using a 17-year database, we investigated how age, breeding experience, location experience, and pair-bond experience influenced Piping Plover (Charadrius melodus) reproductive success in the Great Lakes region. Reproductive success was measured as number of offspring fledged per pair for 415 successful nests during 1993–2009. We controlled for individual and site variation with random effects and tested for increased reproductive success associated with age, prior breeding experience, prior location experience, and prior pair-bond experience using generalized linear mixed models. Reproductive success increased with location-specific breeding experience of females and declined when females moved to a new location. After statistically controlling for t...

Resightings of uniquely marked birds from 2001 to 2008 were used to determine winter distributions of 4 breeding populations of a species at risk, the piping plover (Charadrius melodus). Although considerable overlap exists, a distinct pattern in winter distributions was evident. Birds originating from eastern Canada wintered farthest north compared to other populations. Most individuals from the United States Great Lakes were found in South Carolina and Georgia in winter, whereas birds from eastern Canada were found primarily in North Carolina. Although the great majority of birds marked in Prairie Canada were observed wintering in Texas, particularly southern Texas, breeding plovers from the United States Great Plains were more widely distributed on the gulf coast from Florida to Texas. Very few large-scale movements of individuals in winter were reported either within or between years. This study highlights the significance of geographic regions for eastern Canada, the United States Great Lakes, the United States Great Plains, and Prairie Canada populations, and demonstrates relatively high winter site fidelity. This information will help focus conservation efforts for specific breeding populations during the winter. © 2011 The Wildlife Society.

After near extirpation in the early 20th century, Ring-billed Gulls (Larus delawarensis) are currently (2009) the most abundant colonial waterbird nesting on the Great Lakes. Nest count data are reported from four decadal censuses (1976–2009) conducted by the Canadian Wildlife Service and the U.S. Fish and Wildlife Service. Numbers increased from 305,790 nests (1976–80) to a peak of 718,887 nests (1989–90), then decreased to 652,664 (1997–2000) and to 585,984 nests (2007–09). Changes varied spatially after the second census with greatest losses (-38.6%) at North Channel, Georgian Bay and northern Lake Huron colonies, and greatest gains (+324.2%) at Lake Michigan colonies. A total of 472 sites had nests in at least one census (Canada N = 319; U.S. N = 153). Eighteen (3.8%) colonies had >2,000 nests in all four censuses, and had 37.5–41.9% of all nests in each census. Site occupancy was fluid. A high proportion (56.8%, N = 268) of sites contained nests in only one of the four censuses, and few (N ...

Geographically isolated breeding populations of migratory shorebirds may be demographically connected through shared nonbreeding habitats. We used long-term (1998-2008) mark-recapture data on piping plovers (Charadrius melodus) collected from 7 separate studies located throughout North America to conduct a range-wide analysis of after hatch year apparent survival (WAHY). Our objectives were to compare concurrent survival estimates from disparate breeding sites and determine whether estimates followed similar trends or were correlated among breeding populations with shared wintering grounds. Average survival estimates were higher for Great Plains populations (range 5 0.69-0.81) than for Great Lakes and Atlantic Coast populations (range 5 0.56-0.71). Linear trend models indicated that apparent survival declined in 4 out of 7 populations, was unchanged in 3, and was generally highest among Great Plains populations. Based on a post hoc analysis, we found evidence of correlated year-to-year fluctuations in annual survival among populations wintering primarily along the southeastern United States Atlantic Coast and Gulf Coast. Our results indicate shared overwintering or stopover sites may influence annual variation in survival among geographically disparate breeding populations. Declines in piping plover survival are a cause for concern, and our results highlight the need for conservation efforts to include habitat used during the migratory and wintering periods.

In the Great Lakes region, numbers of the Piping Plover (Charadrius melodus) are gradually increasing, but the population of

Leg bands are commonly used to mark shorebird chicks as young as 1-d old, but little is known about the possible impacts of bands on survival of prefledging shorebirds. We used a mark-recapture framework to assess the impact of bands and banding-related disturbance on prefledging survival in a federally endangered population of Piping Plovers {Charadrius melodus) breeding in the Great Lakes region from 2000 to 2008. We banded approximately 96% of all surviving chicks hatched prior to fledging, typically between 5 and 15 d of age. We used a multistate approach in program MARK whereby individuals contributed data as unbanded chicks before capture (N = 1073) and as banded chicks afterward (N = 780). The cumulative probability of surviving through 24 d of age was 0.63 and did not differ between banded and unbanded chicks. In addition, we found a positive effect of banding-related disturbance on survival up to 3 d following banding (s = 0.60 CI: 0.17-1.02), possibly due to increased postbanding vigilance on the part of chicks and adults. Our results indicate that banding has no detrimental effect on survival of Piping Plover chicks prior to fledging and that current capture and banding methods are appropriate for this endangered species. RESUMEN. Anillos plasticos de colores y metalicos no afectan la supervivencia de polluelos de Charadrius melodus

Birds within the orders Charadriiformes (shorebirds, gulls) and Anseriformes (waterfowl) are reservoir hosts for avian influenza (AI) viruses, but their role in the transmission dynamics of AI viruses is unclear. To date, waterfowl have been the predominant focal species for most surveillance and epidemiological studies, yet gulls, in particular, have been shown to harbor reassortant AI viruses of both North American and Eurasian lineages and are underrepresented in North American surveillance efforts. To address this gap in surveillance, 1346 ring-billed gulls (Larus delawarensis) were sampled during spring and fall migrations and at three breeding sites in 2017 across Minnesota. Results indicate noticeable age-cohort dynamics in AI virus prevalence within ring-billed gulls in Minnesota. Immunologically naive juveniles represented the cohort with the highest prevalence rate (57.8%). Regardless of age, more gulls had AI virus detected in oropharyngeal (OP) than in cloacal (CL) swabs. The high AI virus prevalence within ring-billed gulls, particularly in immunologically naive birds, warrants further targeted surveillance efforts of ring-billed gulls and other closely related species.

The Great Lakes form the largest freshwater island system in the world and provide breeding habitat for a large proportion of the continental population of double-crested cormorants ( Phalacrocorax auritus ). Here, cormorants have a high profile due to conflicts with humans; by 2007, most active (64%) breeding sites in U.S. waters were managed. This study used data from the U.S. Great Lakes Colonial Waterbird Database and The Nature Conservancy's Great Lakes Island GIS database to identify important features of breeding sites in the U.S. Great Lakes and broaden understanding of cormorant presence at the island-landscape scale. Islands 0.5–10 ha were used more frequently than expected, and most sites had remoteness values of ≤ 3 km. Colony size was positively correlated with years occupied and large colonies (> 1000 pairs) developed primarily (95%) on island sites > 1.0 ha. Sites supporting large colonies were more remote than those supporting smaller colonies. Presence of other colonial waterbird species, especially Herring Gulls ( Larus argentatus ), also characterized cormorant sites. Islands used by cormorants comprised a small proportion ( n = 90, 3%) of the U.S. Great Lakes island resource, and

Abandonment was the most frequent cause of nesting failure in Great Lakes Piping Plovers (Charadrius melodus) during 1993–2007, and observations of color-banded adults suggested that most abandonments involved disappearance of attendant adults rather than behavioral decisions by adults to desert their nests. The purpose of our study was to integrate nest-monitoring histories with mark—resighting analyses to determine whether nest abandonment indicated adult mortality or nest desertion. Nesting Piping Plovers had extremely high within-year resighting probabilities (10-day mean p = 0.908 ± 0.025 [SE] ), and cumulative probabilities of being detected approached 1 for individuals that were present on the breeding grounds for ≥20 days post-abandonment. These observations suggested that desertion would be readily identified unless Piping Plovers left the monitoring areas immediately after deserting their nests. None of the 31 that disappeared (as indicated by nest-monitoring histories) was ever observ...

In 1993, a mark-recapture effort was initiated to band annually all Great Lakes Piping Plover nesting adults and offspring. With voluntary reporting by observers, >430 sightings of 154 individually-marked Great Lakes banded birds were documented on the wintering grounds during 1995–2005. This paper reports non-breeding distribution and site-fidelity and identifies Critical Habitat units used by this population during the winter. Information obtained through banded bird sightings indicates that the winter range of Great Lakes Piping Plovers extends from North Carolina to Texas, and the Bahamas, with the majority (75%) of reported individuals wintering in Georgia and Florida. About 95% of sightings were near or within federally-designated winter Critical Habitat for Piping Plovers. Within season (52%) and between-year (62%) site fidelity was documented for resightings within 3.5 km of initial sighting. Although breeding pairs do not winter in close association, there is some evidence to suggest th...

Canadian and US federal wildlife agencies completed three surveys (1976–1980, 1989–1991, and 1997–2000) to census colonial waterbirds breeding on the Great Lakes. We here summarize and comment on nest numbers and colony site distribution of common terns ( Sterna hirundo ) and Caspian terns ( Hydroprogne caspia ). Common terns are in serious trouble on the Great Lakes. Numbers declined with substantial losses in nests (− 19.1%) and colony sites (− 23.2%) between the first and third censuses. An increase in numbers at US sites (+ 26.6%) did not compensate for losses (− 33.1%) at Canadian sites. Caspian terns increased in nest numbers (+ 65.9%) and colony sites (+ 50.0%) over the same period. The increase at US sites (136.5%) was greater than at Canadian sites (11.5%). Most (70.7%, n = 186) common tern sites had nests during only one census; 17 sites (6.5%) had nests during all censuses. In contrast, 9 of 33 (27.2%) Caspian tern sites had nests during all censuses and contained a majority of nests (50–82%) in each census. Pairs of both species nested on natural substrates across the Great Lakes. Common terns nested mostly on artificial (human-constructed) substrates on the lower Great Lakes. We identify site characteristics that may have contributed to long-term (three census) occupancy by common terns (small size, artificial substrates, absence of ring-billed gulls) and Caspian terns (natural substrates on large, remote islands). We suggest an urgent need for protection and conservation of common tern colonies and identify specific priority sites for implementation of management protocols.

Since 1992, efforts to recover the US federally endangered Great Lakes piping plover ( Charadrius melodus ) have included population supplementation with captive-reared young raised from abandoned eggs. Using banding data collected 1993–2008 and Cormack–Jolly–Seber models in program MARK we estimated resighting rates ( ρ ) and apparent survival ( Φ ) of first-year (1) and after-first-year (2+) plovers. Reproductive success was measured by estimating mean number of eggs laid, chicks hatched and chicks fledged per wild-reared or captive-reared parent, and these values were compared with a permutation test. The best-supported mark-resighting model indicated wild-reared plovers had higher Φ 1 and Φ 2+ than captive-reared plovers. Breeding propensity influenced detection of wild plovers, whereas unique band combinations facilitated detection of yearling captive-reared plovers. Captive-reared ( n = 10) and wild-reared ( n = 57) plovers laid similar numbers of eggs, but wild-reared plovers hatched 36% more chicks and fledged 56% more young. Reproductive values derived from matrix models suggest captive-reared piping plovers are less fit than similarly aged wild-reared birds upon release and demonstrate reduced fitness in subsequent years. The Great Lakes captive-rearing effort has successfully produced a minimum of 10 breeding adults from 192 eggs that otherwise would have had no reproductive value; these captive-reared individuals now constitute up to 3% of the total population. Small scale salvage and captive-rearing of abandoned eggs should be considered as a technique to supplement existing recovery efforts in highly imperiled populations.

Most migrant shorebirds require coastal and estuarine habitat in the nonbreeding season and their overwinter survival is contingent upon the composition and quality of these winter sites. The purpose of this study was to investigate the relationship between the distribution and abundance of the piping plover, a federally threatened and endangered shorebird, and its nonbreeding habitat along the Gulf of Mexico coastline. We identified sites consistently used by wintering piping plovers and quantified landscape and anthropogenic features within a subset of those locations. Using published literature, we documented that piping plovers consistently winter at 49 locations on the U.S. Gulf of Mexico coast (Marco Island, Florida to Padre Island, Texas). At 31 sites, we conducted a remote analysis of aerial photos for 11 features (e.g., intertidal area, urban area, beach). Linear regression was used to test correlations between plover abundance and landscape characteristics. We found that certain shoreli...

In North America, the Double-crested Cormorant (Phalacrocorax auritus) is currently abundant, widely distributed across five broad geographic regions, and often perceived as overabundant. In many U.S. states and Canadian provinces, policy makers are pressured to significantly reduce cormorant numbers, primarily to minimize conflicts between cormorants and fish resources. Concurrently, large-scale conservation plans recently developed for birds in the Americas depart from the traditional narrow focus on threatened and endangered species to encompass broader and more representative goals (e.g., Partners in Flight’s objective to “keep common birds common”). In recent waterbird conservation initiatives, historic distribution and abundance provide the basis for conservation focus; these initiatives advocate conservation of birds in natural numbers and natural habitats. To provide a context in which current populations of Double-crested Cormorants can be understood, we reviewed historic and current bre...

Complete population estimates for widely distributed species are rarely possible. However, for the third time in 10 years, an International Piping Plover (Charadrius melodus) Breeding and Winter Census was conducted throughout the species range in 2001. Nearly 1,400 participants from 32 U.S. states and Puerto Rico; 9 Canadian provinces; St. Pierre and Miquelon, France; Cuba; and the Bahamas visited 2,244 sites covering 11,836 km of shoreline habitat. During the winter census, 2,389 piping plovers were observed at 33.5% of potentially occupied sites (n = 352). Of these, 56.8% had ≤ 10 birds present. The breeding census recorded 5,945 adults at 777 of 1,892 sites surveyed. More than 80% of sites with piping plovers present had ≤ 10 birds. Results indicated an 8.4% increase from 1991 but only a 0.2% increase since 1996. Regional trends suggest that since 1991, number of breeding birds increased on the Atlantic Coast by 78% (2,920 birds; 12.4% increase since 1996) and by 80% in the Great Lakes (72 bi...

This paper introduces the second Special Publication of the Waterbird Society to address the biology and management of the Double-crested Cormorant (Phalacrocorax auritius) in North America. Since the late 1960s and early 1970s, when the species was at very low population levels, the Double-crested Cormorant has rebounded to its greatest population level in over 100 years. Such a significant increase has resulted in changes in community structure, and new stressors, in many aquatic ecosystems. Both Special Publications (1995 and 2013) have been focused on the biology and management of the species. The first volume dealt mainly with population growth and the resulting, immediate management issues. In the current volume, studies address the longer term situation, the implementation of two U.S. depredation orders and new research directions identified in the first Special Publication and in subsequent smaller cormorant symposia. Seventeen papers which comprise this volume are presented under six he...

There are two recognized subspecies of the Piping Plover (Charadrius melodus): the Atlantic coast United States and Canada (‘Atlantic’) subspecies and the Great Lakes and Northern Great Plains (‘Interior’) subspecies. More than 7,000 Piping Plovers have been banded and monitored since 1982, yet no individual marked as a hatchling or breeding adult in the range of one subspecies has been reported breeding in the range of the other. Recent molecular genetic analyses further support subspecific taxonomic classification of Atlantic and Interior breeding populations. On 22 May 2011, a banded Piping Plover and unbanded mate were observed nesting on North Core Banks, Cape Lookout National Seashore, North Carolina, USA. The uniquely-banded adult was a female captured as a chick at Wasaga Beach, Georgian Bay, Ontario, Canada; the female nested unsuccessfully in its first breeding year at Tawas Point State Park, Michigan, USA and then successfully fledged two chicks in its second breeding year at North Co...

This study examined the influence of forest context on woodpecker nest tree selection, which has implications for forest managers leaving trees during timber harvest for cavity nesting birds. We surveyed habitat variables in 11.3 m radius subplots centered on 165 active woodpecker nest trees and 144 randomly selected points in oak forests of southeastern Minnesota and western Wisconsin in 1997–1998. Forward stepwise sequential F -tests indicated that the number of potential nest trees and basal area (BA) of dead elms were the most important variables in distinguishing nest sites and random sites. Discriminant function analysis correctly classified 71% of the observations. However, a comparison of nest sites only to those random sites containing a tree likely suitable for nesting showed no differences. This suggests that nest tree has a greater influence in nest site selection than does surrounding vegetation. Yellow-bellied sapsucker nest trees were surrounded by a significantly higher BA of trembling aspen ( Populus tremuloides ) and density of mast-producing trees than the nest trees of the downy, hairy, red-bellied, red-headed, and pileated woodpeckers, and the northern flicker. However, we found no interspecific differences among downy, hairy, red-bellied, and red-headed woodpeckers. This study is significant because it indicates forest management for cavity nesting birds should focus on providing suitable nest trees within the larger forest context; vegetation immediately surrounding nest trees may have minimal influence on woodpecker nest tree selection.

With recovery of double-crested cormorants ( Phalacrocorax auritus ) in the Great Lakes region, their numbers have increased significantly leading to concern about potential impacts on other species. Cormorants are thought to affect co-occurring colonial waterbirds by usurping limited habitat and destroying vegetation used as nest sites by these species. This paper summarizes initial results from a study to assess potential impacts of double-crested cormorants on great blue herons ( Ardea herodius ) and black-crowned night-herons ( Nycticorax nycticorax ) in the Great Lakes. The study examined population trends, interspecific interactions, and cormorant impacts on vegetation. Despite a steady increase in breeding cormorants in the U.S. Great Lakes over the past two decades, population trends of great blue herons and black-crowned night-herons do not indicate cormorants have negatively influenced breeding distribution or productivity of either species at a regional scale. Cormorants have caused total or partial loss of forest cover at a number of islands in the U.S. Great Lakes and these initial data suggest soil chemistry at cormorant colony sites will affect normal plant growth and survival. However, site use data and field observations indicate double-crested cormorant presence has not caused black-crowned nightheron or great blue heron declines or abandonment except under special circumstances. Although preliminary, these results suggest cormorant control policy should not be justified by assumption of potential impacts on other waterbird species without careful documentation.

We created a stochastic habitat-based population model to compare the relative effectiveness of potential conservation strategies to increase the endangered Great Lakes population of piping plovers. Initial model parameters were based on an extensive 14-year dataset obtained by annual studies of breeding pairs in Michigan and 6 years of observations of color-marked individuals. Cumulative persistence probability curves and population trends were compared for scenarios with all possible combinations of the following: (1) empirical, medium and high site specific probabilities of reproductive success and (2) empirical, medium and high numbers of available breeding territories. Sites were also categorized according to land ownership to determine if long-term preservation of publicly owned lands is sufficient for population recovery under any of the scenarios. Only scenarios in which both reproduction and habitat availability were high and all ownership classes were included resulted in a model population that persisted for 100 years and was likely to reach the US Fish and Wildlife Service current population recovery goal (100 breeding pairs) for Michigan. The model was most sensitive to survival rates of adults and more sensitive to changes in reproductive parameters than to number of breeding sites or territories. Model results suggest that intensive measures to increase productivity alone are not sufficient for population recovery; increases in nesting densities or total number of available territories are also likely necessary. Given uncertainties about nesting densities possible at specific breeding sites, preservation of presently unoccupied habitat throughout the Great Lakes region and management of this habitat to encourage breeding by plovers are recommended. Use of techniques to augment the breeding population in conjunction with protection of habitat and reproduction may be warranted.

Techniques for captive-rearing and releasing piping plovers (Charadrius melodus) were developed using a surrogate species, killdeer (Charadrius vociferus). We compared captive- and parent-reared killdeer, and parent-reared piping plovers and determined that growth and behavior were similar. After surrogate trials determined that captive-rearing was feasible, we used the same methods to raise piping plover chicks from salvaged eggs. For captive-reared chick of both species, survival to fledging was higher than and behaviors similar to parent-reared chicks in the wild. Rearing techniques were fine-tuned, and ten piping plover fledglings were released to the wild. Based on our results, we developed recommendations for captive-rearing piping plovers using salvaged eggs to enhance productivity of small populations. Zoo Biol 16:461‐477, 1997. © 1997 Wiley-Liss, Inc.

The common palm civet, Paradoxurus hermaphroditus , was studied in Royal Chitwan National Park, Nepal, to determine daily and seasonal movements in relation to availability of food and predation pressure. Five adult animals (two females and three males) were captured and fitted with radiocollars and located every other day. Each animal was followed for 12 consecutive h/month. Palm civets were strictly nocturnal; activity began at ca. 1800 h and ended at ca. 0400 h. Animals were more active on dark nights than on bright, moonlit nights and typically rested during the day in the crown of vine-covered trees. Seeds of fruits were found in 84.5% of 193 scats of palm civets that were collected December 1989 to June 1990. In April, when ripe fruits were not readily available, a shift in diet from fruits to vertebrate and invertebrate prey occurred. Palm civets also fed on the nectar of Bombax ceiba and sap from stems of Vallaris solanacea . Home-range sizes varied inversely with the amount of food available. A high degree of home-range overlap indicated that individuals were not territorial. Documented predation and exclusive nocturnal activity suggest that palm civets are vulnerable to predation by large carnivores in the park. Strong predation pressure and high temporal and spatial variation in availability of food resources may account for the apparent absence of territorial behavior of palm civets in this population.

This study compared the growth and behavioral development of parent-reared, cross-fostered, and captive-reared Killdeer (Charadrius vociferus) chicks. Common species were used to test these techniques for possible application to rare endangered forms. Parent-reared chicks were raised naturally in the wild, cross-fostered chicks were raised by Spotted Sandpipers (Actitis macularia) in the wild, and captive-reared chicks were raised in captivity by humans. Both hatching and fledging success were significantly increased by captive-rearing, and cross-fostering produced approximately the same number of fledged young as natural parent-rearing. Captive-reared Killdeer chicks spent more time resting and less time feeding and stayed closer to siblings than cross-fostered or parent-reared chicks; these behavioral differences were not seen after release to the wild. Growth rates among the three groups were similar. All of the young Killdeer responded to Killdeer alarm calls. There was no evidence that captive-reared and cross-fostered Killdeer were negatively affected by their early experiences. Captive-rearing is a viable management technique for augmenting small populations of endangered shorebirds, such as the Piping Plover (Charadrius melodus). It is recommended over cross-fostering because captive-rearing is more flexible as a technique, produces more young, does not affect another species, and does not produce potential imprinting problems. Este estudio comparo el crecimiento y desarrollo del comportamiento de pichones de chorlitejo culirrojo (Charadrius vociferus) criados bajo tres regimenes distintos: criados por sus progenitores, criados bajo adopcion cruzada y criados en cautiverio. Especies comunes fueron usadas para testear estas tecnicas para su posible aplicacion en especies raras y en peligro de extincion. Los pichones criados por sus progenitores fueron criados en estado salvaje, los pichones criados bajo adopcion cruzada fueron criados por andarrios maculados (Actitis macularia) en estado salvaje, y los pichones criados en cautiverio fueron criados por humanos. El exito en eclosionar y comenzar a volar fue significativamente incrementado por medio de la crianza en cautiverio; la adopcion cruzada produjo aproximadamente el mismo numero de jovenes que comenzaron a volar que la crianza por progenitores naturales. Los pichones de chorlitejo culirrojo criados en cautiverio pasaron mas tiempo descansando y menos tiempo alimentandose, y estuvieron mas cerca de sus hermanos que los criados por adopcion cruzada o por sus progenitores naturales; estas diferencias en el comportamiento no fueron observadas luego de ser puestos en libertad. Las tasas de crecimiento de los tres grupos fueron similares. Todos los chorlitejos culirrojos juveniles respondieron a las llamadas de alarma de otros chorlitejos culirrojos. No existio evidencia de que los chorlitejos culirrojos criados en cautiverio y en adopcion cruzada estuviesen afectados negativamente por sus experiencias tempranas. La crianza en cautiverio es una tecnica de manejo viable para promover el crecimiento de poblaciones pequenas de pajaros costeros como el “piping plover” (Charadrius melodus). Se recomienda antes que la adopcion cruzada porque la crianza en cautiverio es mas flexible como tecnica, produce mas juveniles, no afecta otras especies, y no produce problemas potenciales de “imprinting”.

Characteristics of woodpecker nest trees have been widely studied in some regions of North America. However, there is little research from the Upper Midwest. Forest managers need information on woodpecker nest tree characteristics so they can recommend leaving during harvest trees that meet the needs of cavity-dwelling wildlife. Information specific to the Upper Midwest is especially important given that declines in several species of cavity nesting birds have been predicted by an environmental analysis of timber harvest in Minnesota. Our purpose was to identify attributes of nest trees used by primary cavity-nesting birds. We compared nest trees to unused trees and examined differences in nest trees among woodpecker species. We found 166 active woodpecker nests in upper midwestern oak forests in 1997 and 1998. For each nest tree, we recorded height, diameter, status, and aspects of tree decay. We also measured four potential nest trees (non-nest trees, within size requirements of cavity-nesting birds, with at least 2 indicators of heartwood decay) closest to each active nest tree. Additionally, we recorded these measurements for 137 randomly selected potential nest trees. Using paired t-tests and chi-square analysis, we found each woodpecker species had a unique set of characteristics that separated nest trees from potential nest trees. Using an extension of the McNemar test for related samples, we found woodpeckers as a group used trees that were larger, both in diameter and height, more often elm (Ulmus americana, U. rubra) or aspen (Populus tremuloides, P. grandidentata), more likely to have old cavities present, and with more decay indicators than adjacent potential nest trees. The Yellow-bellied Sapsucker (Sphyrapicus varius) differed from the other woodpecker species by nesting in living Trembling Aspens (Populus tremuloides) with intact tops, complete bark cover, and heartwood fungus. Diameters of nest trees differed significantly among woodpecker species, but unlike findings from other studies, the height of nest hole and nest tree did not. Woodpecker nest entrances faced south or southeast significantly more often than by chance alone, even when excluding leaning trees. This study suggests that generic forest management for all woodpecker species may not be adequate because individual species have specific nest tree requirements. Management recommendations for cavity-nesting birds need to be tailored to meet the needs of a diversity of species.

Forest fragmentation has been implicated as a cause of population declines of several Neotropical migrant bird species. Fragmentation increases the amount of habitat edge, and reduced nesting success rates near forest edges are well documented in agricultural landscapes (“edge effects”). However, edge effects in predominantly forested landscapes, particularly those related to timber harvest, are poorly understood. This study examines nesting success of ground nesting birds in relation to clearcut edges in a forest-dominated landscape in north-central Minnesota. A total of 383 nests of seven species of ground nesting birds were found and monitored during 1992–1998. Ovenbird (Seiurus aurocapilus; n = 318) and Hermit Thrush (Catharus guttatus; n = 44) nests composed the majority of the sample. Predation accounted for 94% of all nest failures. Brown-headed Cowbird (Molothrus ater) parasitism was low (1.8% for all ground nests). Using proportional hazards regression, distance to nearest clearcut edge ...

The breeding range of the Caspian Tern (Sterna caspia) covers large parts of six geographic regions in North America. We obtained data from individuals who monitor colonial waterbirds to determine current status and distribution of the Caspian Tern in the U.S., Canada and Mexico and to report regional population trends. We estimate 32,000-34,000 pairs nested in North America from the late 1980s to 1998. The species' breeding range is expanding along the Pacific coast and in central Canada. Over the last three decades numbers of breeding pairs have significantly increased in the Great Lakes, central Canada, and along the Gulf and Pacific coasts; the Atlantic coast is the only region where significant decline has occurred. On the Pacific and Gulf coasts, large numbers of Caspians utilize artificial habitat (e.g., dredge spoil islands, salt dikes and levees, landfills, artificial lakes). Changes in food supply may be at least partly responsible for population increases in the Great Lakes, on the Pacific coast, and in central Canada in Manitoba. Other factors that may contribute to increases include creation of artificial habitat that Caspian Terns find attractive for nesting, and legislation that protects Caspian Terns and their habitat. Received 15 Mar 1999, accepted 19July 1999.

Caspian Tern (Sterna caspia) breeding colonies exhibit a disjunct distribution on all continents except South America where they apparently do not nest. On the North American continent, breeding colonies are located in at least 6 geographical regions which are separated by more than 500 km (see Voous 1960, Martin 1978). Current evidence for Caspian Terns (Ludwig 1968, in prep.) and other larids (Austin 1940, Mills 1973, Harrington 1974, Ludwig 1968, Chabrzyk and Coulson 1976, Southern 1977) is that offspring tend to return to the region of their natal colony to breed. This tendency, and the geographical separation between Caspian Tern breeding areas in North America suggests there is little mixing between areas, and that birds in each region comprise a population that maintains itself primarily through reproduction. It is conceivable, therefore, that one population could decline dramatically because of local perturbations while other populations were unchanged. The possibility of a local decline would be greatest for small, discrete populations particularly if the birds nested at only a few colonies.