Core Breeding Area Research Articles

Bat Assemblages Are Shaped by Land Cover Types and Forest Age: A Case Study from Eastern Ukraine

Eastern European broadleaved forests north of the 50th degree of latitude serve as a core breeding area for most migratory bat species wintering in Eastern and Central Europe. The southern border of this region has faced an increase in clear-cutting intensity in recent decades. We conducted a standardized mist-netting survey on eleven heterogeneous oak forest plots in order to assess how land cover types and forest age affect abundance, diversity and the breeding of bats. We found that abundance indices and species richness increased from upland plots surrounded by agricultural lands to riverine or waterside plots with high forest cover. Particularly large mature forests older than 90 years positively affected the breeding activity of bats, their abundance indices and overall species richness. Regarding species associations with specific habitats, we found that Myotis brandtii, Nyctalus leisleri and Pipistrellus pygmaeus were mainly found in mature deciduous forest stands, while Plecotus auritus appeared to be the only species tolerating clearcuts and young stands. Forest-dwelling species such as Nyctalus noctula and Pipistrellus nathusii were additionally associated with water habitats. Thus, the combination of mature forests and water sources is essential in shaping Eastern European assemblages of forest bat species.

Decline of Eastern Black Rails (Laterallus jamaicensis jamaicensis) within the Chesapeake Bay Region, USA

Eastern Black Rails (Laterallus jamaicensis jamaicensis) were surveyed during 1990, 2007, 2014 within the Chesapeake Bay region in Maryland and Virginia, USA. A network of point count locations (n = 182) was established and surveyed within tidal salt marshes. Occupancy declined during the study period from 0.84 ± 0.13 (ψ ± SE) in 1990 to 0.06 ± 0.02 in 2014. The annualized rate of decline was estimated to be 6.5%. Extinction and colonization rates between 1990 and 2014 were 0.81 ± 0.09 and 0.04 ± 0.02 respectively. Abundance declined from 1.98±0.05 Black Rails/point in 1990 to 0.26 ± 0.02 in 2014 with a 3.2% annualized rate of decline. Recruitment was 1.32 ± 1.35 between 1990 and 2007 and 0.003 ± 0.05 between 2007 and 2014. Species detection was negatively influenced by advancing season and waxing moon phase while individual detection was most strongly influenced by survey year and advancing season. Anecdotal observations of range-wide strongholds within the Chesapeake Bay suggest that sites have experienced significant declines with birds being extirpated by 2016. Declines throughout the core breeding area and within individual strongholds in the Chesapeake Bay are consistent with Black Rail declines in tidal habitats throughout the broader Northeast region.

Using ensemble modeling to predict breeding habitat of the red-listed Western Tragopan (Tragopan melanocephalus) in the Western Himalayas of Pakistan

Quantifying a species geographic range is a necessary requirement for targeted and effective conservation management and planning. The Western Tragopan ( Tragopan melanocephalus ) is a globally threatened Galliformes, endemic to the Western Himalayas. The breeding habitat of the species is believed to be exposed to increased anthropogenic pressures. There is a general lack of empirically-based approaches to protect the breeding habitat of this species. To this end, we used recent records of breeding tragopan to develop an ensemble model of the breeding habitat in Pakistan for this Vulnerable species. The model predicted a total area of 10,410 km 2 as potential breeding habitat for the species nationally. Of this, 2979 km 2 (28.6%) were potentially highly suitable (P > 0.4), 2544 km 2 (24.4%) were moderately suitable (0.2 >P < 0.4), and 4887 km 2 (46.9%) were of low suitability (P < 0.2). The breeding sites of the species were recorded with mean global human modification gradient of 0.33 ± 0.06 which implies that habitat suitability for the Tragopan now appears associated with areas of moderate land modification. Therefore, the predicted highly suitable area (core breeding area) was only 79 km 2 (or 2.6%) of the total predicted area suitable for breeding. Hence, the potential breeding habitat of this species may be degraded owing to human habitat interference. We propose that the remaining pockets of high suitability for breeding which remain free from human impacts are declared as protected areas with immediate effect. Areas of high suitability with already existing human disturbance should receive high attention by conservation managers and policy makers, attempting to reduce further human impact. Our model further suggests that more detailed studies at a landscape level should be carried out urgently to successfully protect this globally threatened species from further habitat deterioration.

Population size and spatial distribution of the white stork Ciconia ciconia in Poland in 1958 with insights into long-term trends in regional and global population

Although white stork Ciconia ciconia counts go back to the XIX century, making the species a model in population investigations, substantial gaps remain in the knowledge of its large-scale population dynamics. In particular, incomplete past estimates from the core breeding areas leave the long-term changes uncertain. In this paper, we provide the earliest estimation of population size and spatial distribution of the white stork in its main stronghold (Poland) to reconstruct the species long-term trends. Based on original survey data collected during the 2nd (1958, incomplete in Poland) and 3rd (1974, successful) International White Stork Census (IWSC) we compared stork numbers in a random sample of villages surveyed on both occasions. We applied linear models to estimate the population growth rate between 1958 and 1974 and to assess spatial variation in population change across the country. Finally, we collated worldwide stork numbers obtained from all IWSCs and discuss the long-term population trends in light of new data. The stork population in Poland in 1958 was estimated at 46,100 breeding pairs and the nationwide density at 14.7 pairs/100 km2. A strong decline (by 30.2%, 1.88% per year) was noted between 1958 and 1974 across Poland with prominent spatial variation reflecting differences in local densities. The strongest declines in absolute terms affected the most abundant populations in Eastern Poland. Our data show that in the mid-20th century, the stork population in Poland was close to the current level, but it experienced a massive decline during the 1960s–1980s. This decline was consistent with trends in the worldwide and regional European populations, contrary to earlier statements indicating limited, if any, changes in the core European area. Overall, our data expand knowledge on the long-term dynamics in the white stork numbers and show that even massive changes may easily go undetected if based on non-solid data.

Collision risk of Montagu’s Harriers Circus pygargus with wind turbines derived from high‐resolution GPS tracking

Flight behaviour characteristics such as flight altitude and avoidance behaviour determine the species‐specific collision risk of birds with wind turbines. However, traditional observational methods exhibit limited positional accuracy. High‐resolution GPS telemetry represents a promising method to overcome this drawback. In this study, we used three‐dimensional GPS tracking data including high‐accuracy tracks recorded at 3‐s intervals to investigate the collision risk of breeding male Montagu's Harriers Circus pygargus in the Dutch–German border region. Avoidance of wind turbines was quantified by a novel approach comparing observed flights to a null model of random flight behaviour. On average, Montagu's Harriers spent as much as 8.2 h per day in flight. Most flights were at low altitude, with only 7.1% within the average rotor height range (RHR; 45–125 m). Montagu's Harriers showed significant avoidance behaviour, approaching turbines less often than expected, particularly when flying within the RHR (avoidance rate of 93.5%). For the present state, with wind farms situated on the fringes of the regional nesting range, collision risk models based on our new insights on flight behaviour indicated 0.6–2.0 yearly collisions of adult males (as compared with a population size of c. 40 pairs). However, the erection of a new wind farm inside the core breeding area could markedly increase mortality (up to 9.7 yearly collisions). If repowering of the wind farms was carried out using low‐reaching modern turbines (RHR 36–150 m), mortality would more than double, whereas it would stay approximately constant if higher turbines (RHR 86–200 m) were used. Our study demonstrates the great potential of high‐resolution GPS tracking for collision risk assessments. The resulting information on collision‐related flight behaviour allows for performing detailed scenario analyses on wind farm siting and turbine design, in contrast to current environmental assessment practices. With regard to Montagu's Harriers, we conclude that although the deployment of higher wind turbines represents an opportunity to reduce collision risk for this species, precluding wind energy developments in core breeding areas remains the most important mitigation measure.

Occupancy Patterns of Breeding American Black Ducks

ABSTRACTOccupancy patterns can assist with the determination of habitat limitation during breeding or wintering periods and can help guide population and habitat management efforts. American black ducks (Anas rubripes; black ducks) are thought to be limited by habitat and food availability during the winter, but breeding sites may also limit the size or growth potential of the population. The Canadian Wildlife Service conducts an annual breeding waterfowl survey that we used to explore the hypothesis that black duck carrying capacity is limited by wetlands available for breeding in Québec, Canada. We applied single‐visit, multi‐species occupancy models to the 1990–2015 population survey data to determine if there was evidence the black duck population was limited by breeding habitat. Using a dynamic (multi‐season) occupancy modeling approach, we estimated latent occupancy (occupancy accounting for imperfect detection) of black ducks and then used latent occupancy estimates to derive occupancy, colonization, and extirpation rates. We jointly modeled the occupancy dynamics of black ducks and other duck species in wetlands where both species were present. Throughout the duration of the survey, 44% of wetlands were never observed to be occupied by black ducks. Occupancy models showed wetland size was positively associated with occupancy at the first time step (initial occupancy) and colonization. All 2‐species models indicated initial black duck occupancy, persistence (continued occupancy), and colonization were positively associated with the presence of a second species. Colonization rate over the 26‐year period ranged from 7% to 27% across all models. Extirpation rates were similar and were constant through time within each model. Low occupancy rates, combined with approximately equal colonization and extirpation rates, suggest there are available wetlands for breeding black ducks in their core breeding area. If breeding habitats are not saturated, this suggests migration or wintering areas may be more limiting to black duck population abundance. © 2019 The Wildlife Society.

Monarch Habitat as a Component of Multifunctional Landscape Restoration Using Continuous Riparian Buffers

Stabilizing the eastern, migratory population of monarch butterflies (Danaus plexippus) is expected to require substantial habitat restoration on agricultural land in the core breeding area of the Upper Midwestern U.S. Previous research has considered the potential to utilize marginal land for this purpose because of its low productivity, erodible soils, and high nutrient input requirements. This strategy has strong potential for restoring milkweed (Asclepias spp.), but may be limited in terms of its ability to generate additional biophysical and socioeconomic benefits for local communities. Here we explore the possibility of restoring milkweed via the creation of continuous riparian buffer strips around perennial and intermittent streams throughout the region. We use a GIS-based analysis to consider the potential of several different buffer-width scenarios to meet milkweed restoration targets. We further estimate the ability of these habitat areas to provide additional functionality in the form of crop pollination and water quality regulation across the entire region. Finally, we estimate the conservative economic value of these ecosystem services and compare it with the lost value of crops associated with each scenario. Results suggest that riparian buffers could be used to meet 10-43% of the total milkweed restoration target of 1.3 billion new stems with moderate management. The value of water quality and pollination benefits provided by buffers is estimated to exceed costs only for our smallest buffer-width scenario, with a cost-benefit ratio of 1:2.05. Larger buffer widths provide more milkweed, but costs to farmers exceed the benefits we were able to quantify. The large-scale restoration of multifunctional riparian corridors thus has the potential to add milkweed stems while also providing a variety of other valuable benefits. This suggests the potential to leverage monarch habitat restoration efforts for the benefit of a wider variety of species and a broader coalition of beneficiaries.

A gloomy future for light-bellied brent geese in Tusenøyane, Svalbard, under a changing predator regime

The endangered population of light-bellied brent geese (Branta bernicla hrota) breeding in Svalbard and north-east Greenland used to have its core breeding area in the archipelago of Tusenoyane in south-east Svalbard. Studies carried out during 1987–1991 showed that the Tusenoyane population was subject to heavy egg predation by polar bears and, in one year, Arctic foxes. Revisiting some key nesting islands in August 2018, we found few nests used by brent geese and no families. The high density of common scurvygrass (Cochlearia officinalis), a food favoured by brent geese and therefore formerly depleted by them, indicates that the geese have been absent for some time. Among other bird species, such as barnacle goose and common eider, very few young were observed as well. As potential predators, polar bears, or signs of their recent presence, were observed on most islands, and great skuas occurred on almost all islands, with 60 individuals on Luroya, formerly an important island for geese. In contrast, only a single pair of great skuas was observed 30 years ago. The observations suggest that recent expansion of great skuas in the North Atlantic, including Svalbard, has led to a novel extreme predation pressure, additional to that caused by mammalian predators. Despite the loss of Tusenoyane as a breeding ground, the population of brent geese has increased in recent decades; so we can infer that the population now recruits from remote but mainly unknown breeding grounds.

Analysis of the Genetic Diversity and Structure of the Grey-Faced Buzzard (Butastur indicus) in Japan, Based on mtDNA.

The grey-faced buzzard (Butastur indicus) is a raptor that inhabits East Asia, including Japan. Because the number of individuals has decreased by 75% over the last 40 years, this species is classified as vulnerable (VU) in Japan. In the present study, wesought to reveal the genetic structure of the Japanese grey-faced buzzard population at several breeding sites, and to assess the levels of genetic diversity within the Japanese population. We sequenced 555 bp of the mitochondrial DNA of 96 individuals sampled during the breeding season at 18 sites, and 11 individuals sampled during the winter season at one site. In total, 21 variable sites were found in the control region, and we detected 26 haplotypes among the 107 individuals. Fukuoka represented the core breeding area for grey-faced buzzards, as half of all haplotypes were detected there. Four unique haplotypes were detected in the overwintering area. The results of the network and mismatch distribution analyses indicated that the grey-faced buzzard has not experienced a genetic bottleneck in the past, but did experience recent population expansion. In addition, comparisons with other raptors revealed rich genetic diversity in the grey-faced buzzard population. Our results indicate that conservation of both breeding and wintering areas is important for the protection of the grey-faced buzzard.

Managing forest habitat for conservation-reliant species in a changing climate: The case of the endangered Kirtland’s Warbler

Conservation and recovery of species of concern necessitates evaluating forest habitat conditions under changing climate conditions, especially in the early stages of the delisting process. Managers must weigh implications of near-term habitat management activities within the context of changing environmental conditions and a species’ biological traits that may influence their vulnerability to changing conditions. Here we applied established population-habitat relationships based on decades of monitoring and research-management collaborations for the Kirtland’s Warbler (Setophaga kirtlandii) to project potential impacts of changing environmental conditions to breeding habitat distribution, quantity, and quality in the near future. Kirtland’s warblers are habitat-specialists that nest exclusively within dense jack pine (Pinus banksiana) forests between ca. 5–20 years of age. Using Random Forests to predict changes in distribution and growth rate of jack pine under future scenarios, results indicate the projected distribution of jack pine will contract considerably (ca. 75%) throughout the Lake States region, U.S.A. in response to projected environmental conditions in 2099 under RCP 4.5 and 8.5 climate scenarios regardless of climate model. Reduced suitability for jack pine regeneration across the Lake States may constrain management options, especially for creating high stem-density plantations nesting habitat. However, conditions remain suitable for jack pine regeneration within their historical and current core breeding range in northern Lower Michigan and several satellite breeding areas. Projected changes in jack pine growth rates varied within the core breeding area, but altered growth rates did not greatly alter the duration that habitat remained suitable for nesting by the Kirtland’s Warblers. These findings contribute to Kirtland’s Warbler conservation by informing habitat spatial planning of plantation management to provide a constant supply of nesting habitat based on the spatial variability of potential loss or gain of lands environmentally suitable for regenerating jack pine in the long-term.

Change of foraging behavior of cormorants and the effect on river fish

Since the European population of great cormorants (Phalacrocorax carbo sinensis) rapidly increased 30 years ago, Denmark has been one of the core breeding areas for this colonial water bird. Following a 10-year period with stable breeding numbers in Denmark, the population of great cormorants decreased. At the same time, a combination of cold winters and low availability of coastal prey fish apparently triggered birds to seek new foraging areas. Thus, cormorants began to appear in rivers and streams coinciding with an observed massive decline of fish, mainly brown trout (Salmo trutta) and grayling (Thymallus thymallus). In this paper, we present the results from studies using radio-telemetry, PIT-tagging, and traditional fish surveys to estimate the impact of predation in Danish lowland rivers. Recovery of PIT-tags revealed that an estimated 30% of wild trout and 72% of wild grayling tagged in a small river were eaten by cormorants. In another medium-sized river, 79% of radio-tagged adult grayling were removed, presumably by cormorants during winter. Thus, predation from cormorants appears to be at a level that explains the observed collapse of grayling and brown trout populations in many Danish streams.

Development of a Survey Protocol for Monitoring Reddish Egrets (Egretta rufescens) in Florida, USA

Abstract The Reddish Egret (Egretta rufescens) is North America's rarest heron, and roughly 10% of its population resides in Florida. Its dark plumage, subcanopy nesting, and rarity make it difficult to count with aerial surveys, and assessments of ground- and boat-based methods for estimating the abundance of nesting pairs at breeding sites in Florida are lacking. The efficacy of flight-line surveys (boat-based counts of adults flying to and from colonies) and direct counts (ground- or boat-based counts of nests) were compared using data collected by multiple observers during repeated visits to 16 Reddish Egret colonies in three core breeding areas in the State of Florida, USA. Detection rates on direct counts were 77% for a single observer and 89% for two observers combined. Variance between repeated flight-line surveys was high (61%) for 1-hr surveys but substantially lower for 2-hr (18%) and 3-hr (14%) surveys. Estimated nest counts from flight-line surveys were substantially greater than those produc...

Analysis of the genetic diversity and structure of the Eastern Marsh Harrier in Japan using mitochondrial DNA

The Eastern Marsh Harrier (Circus spilonotus) is a raptor and inhabitant of East Asia, including Japan, and is classified as endangered (class IB) in Japan. The aim of this study was to reveal the genetic structure of a C. spilonotus population among several breeding sites, and to estimate whether the current population contains sufficient genetic diversity. We sequenced 1142 base pairs of the mitochondrial DNA of Eastern Marsh Harrier among 37 individuals sampled during the breeding season and four individuals sampled during winter. In total, seven variable sites were found in the control region, and we detected nine haplotypes among the 41 individuals. Hachirogata, Akita prefecture in Japan, was found to be the core breeding area for the Eastern Marsh Harrier as all haplotypes were detected there. The results of network and mismatch distribution analyses indicated that the Eastern Marsh Harrier did not experience a genetic bottleneck in the past, rather it experienced a recent population expansion. In addition, comparisons with other raptors revealed a rich genetic diversity in the Eastern Marsh Harrier population in Japan.

Using a full annual cycle model to evaluate long‐term population viability of the conservation‐reliant Kirtland's warbler after successful recovery

Summary Long‐term management planning for conservation‐reliant migratory songbirds is particularly challenging because habitat quality in different stages and geographic locations of the annual cycle can have direct and carry‐over effects that influence the population dynamics. The Neotropical migratory songbird Kirtland's warbler Setophaga kirtlandii (Baird 1852) is listed as endangered under the U.S. Endangered Species Act and Near Threatened under the IUCN Red List. This conservation‐reliant species is being considered for U.S. federal delisting because the species has surpassed the designated 1000 breeding pairs recovery threshold since 2001. To help inform the delisting decision and long‐term management efforts, we developed a population simulation model for the Kirtland's warbler that incorporated both breeding and wintering grounds habitat dynamics, and projected population viability based on current environmental conditions and potential future management scenarios. Future management scenarios included the continuation of current management conditions, reduced productivity and carrying capacity due to the changes in habitat suitability from the creation of experimental jack pine Pinus banksiana (Lamb.) plantations, and reduced productivity from alteration of the brown‐headed cowbird Molothrus ater (Boddaert 1783) removal programme. Linking wintering grounds precipitation to productivity improved the accuracy of the model for replicating past observed population dynamics. Our future simulations indicate that the Kirtland's warbler population is stable under two potential future management scenarios: (i) continuation of current management practices and (ii) spatially restricting cowbird removal to the core breeding area, assuming that cowbirds reduce productivity in the remaining patches by ≤41%. The additional future management scenarios we assessed resulted in population declines. Synthesis and applications. Our study indicates that the Kirtland's warbler population is stable under current management conditions and that the jack pine plantation and cowbird removal programmes continue to be necessary for the long‐term persistence of the species. This study represents one of the first attempts to incorporate full annual cycle dynamics into a population viability analysis for a migratory bird, and our results indicate that incorporating wintering grounds dynamics improved the model performance.

Small‐scale spatial and temporal variation in the demographic processes underlying the large‐scale decline of eiders in the Baltic Sea

AbstractThe application of uniform conservation schemes often fails to account for small‐scale spatial variation in the drivers of population decline. Demographic comparisons of imperilled populations across locations are therefore crucial for successful conservation, but progress is hampered by lack of long‐term data from more than a single population. The recent large‐scale decline of eider ducks (Somateria mollissima) in the Baltic Sea is ideal for determining to what extent mechanisms underlying population decline can be extrapolated over larger areas. We utilized stochastic demographic methods incorporating both environmental and sampling variation to assess small‐scale spatial and temporal variation in the population dynamics of eiders at Söderskär (eastern range‐margin) and Tvärminne (core breeding area), situated 130 km apart. The stochastic growth rate models accurately predicted the observed differences in the rate of decline between sites and time periods. At Söderskär, established breeder survival had by far the greatest elasticity, whereas elasticity was more evenly distributed among vital rates at Tvärminne. Although the study sites showed the single largest difference in fecundity, stochastic life table response experiment analyses revealed that reduced adult female survival at Tvärminne mainly determined the observed difference in growth rates between sites. In contrast, reduced fecundity primarily differentiated the past population increase from the present population decline at Söderskär. Our results demonstrate that different mechanisms may be associated with population decline across adjacent geographic locations, and indicate that dispersal of first‐time breeders may be important for population dynamics. Safeguarding adult female survival and/or fecundity should be prioritized in management efforts.

The increase in the Corncrake Crex crex population of the United Kingdom has slowed

Capsule The UK Corncrake population increase has slowed, but has rapidly recovered from a large decline in 2013.Aims To provide an update on the population size and distribution of breeding Corncrakes in the UK, including the results of the most recent full national survey and annual monitoring of the core population.Methods A full survey of singing Corncrakes was undertaken in the UK and the Isle of Man in 2009, following the last full censuses in 1978/79, 1988, 1993, 1998 and 2003. Monitoring of singing male Corncrakes within the core range in northern and western Scotland has been undertaken annually since 1993.Results The 2009 results show that numbers increased substantially since 2003, from 829 to 1166 singing males. Corncrake numbers in the core range have increased in 17 of the 21 years between 1993 and 2014, and peaked at 1274 singing males, in 2014. Numbers of singing males dropped by 24% between 2012 and 2013, probably due to a particularly cold spring in 2013 that inhibited growth of vegetation cover, but numbers recovered markedly in 2014.Conclusion The recovery of the UK Corncrake population has continued since a low point in 1993. However there are no signs of range expansion into mainland UK, away from the core breeding areas in Scotland. The large decline in the core population between 2012 and 2013 highlights the sensitivity of the population to external factors, although the subsequent increase in 2014 shows a capacity for rapid recovery.

Evidence for contrasting causes of population change in two closely related, sympatric breeding species the Whinchat Saxicola rubetra and Stonechat Saxicola torquata in Britain

Capsule The recent population decline of Whinchats has accelerated, including core breeding areas of Britain. Contrasting patterns of change with Stonechat suggest a large-scale environmental driver is affecting the entire Whinchat population.Aims To explore broad geographical and landscape related differences in long-term patterns of population change in the Whinchat and Stonechat across Britain to identify candidate mechanisms of change.Methods The study uses 40 years of large-scale, long-term data from a series of three atlas studies to compare trends in range and abundance in Whinchats and Stonechats relative to landscape and weather variables.Results For Whinchats there has been a long-term and accelerating decline in abundance, that includes stronghold areas of Britain. The Stonechat population has undergone a net gain in abundance with regional and altitudinal variations. These two very different patterns of change suggest the relative ubiquity of decline in Whinchats has a common source affecting the whole population.Conclusions The scale and magnitude of decline in Whinchats should stimulate a revision of the species conservation status in Britain, with renewed focus on studying the species' ecology across its breeding and winter range in order to determine the likely large-scale drivers of its decline.

EU protection is inadequate for a declining flyway population of Black-tailed Godwit Limosa limosa: mismatch between future core breeding areas and existing Special Protection Areas

SummaryThis study analyses whether effective conservation of Black-tailed Godwit Limosa limosa breeding populations in the Netherlands can be achieved through the EU network of Special Protection Areas (SPAs). An internationally important number of pairs of Black-tailed Godwit breeds in the Netherlands but the breeding population is declining steeply and is, in effect, unprotected, as the Netherlands has not designated SPAs for it. To contribute to firmer and more efficient protection of the Black-tailed Godwit, we set out to identify the core areas in the Netherlands where this species is expected to breed in 2020. On the basis of an optimal combination of three main habitat requirements (groundwater level, land-use and openness of the landscape) we identified five core areas in lower-lying (western) Netherlands: Zuidwest Friesland, Waterland, the IJssel delta area, Arkemheen and Eem polders, and Groene Hart. Because these areas are currently not designated for the breeding period of Black-tailed Godwit within the SPA network, the protection of this flagship species of Dutch meadows could be at risk. It seems likely that the Black-tailed Godwit population will continue to decline, with the result that the Netherlands will breach several policy commitments for the conservation of this species.

Reproductive ecology of American Oystercatchers nesting on shell rakes

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 flood events or predators by relocating to higher or more protected portions of a shell rake. Based on comparative data for American Oystercatchers from elsewhere in their range, it does not appear that shell rakes in the Cape Romain region are inferior breeding habitat. Our data suggest that conservation actions targeting nest and chick loss from flooding and predation have the greatest opportunity to enhance reproductive success in this core breeding area, and that an assessment of the availability, structure, avian use, and protection status of shell rakes is warranted.

Daily survival rate for nests of Black Skimmers from a core breeding area of the southeastern USA

Little is known about the reproductive success of Black Skimmers (Rynchops niger) throughout the southeastern USA where availability of undisturbed beaches for nesting is limited. Daily survival rates (DSR) of nests were examined at three nesting sites in Cape Romain National Wildlife Refuge (CRNWR), South Carolina, USA, 2009–2010. The percent of successful nests (n = 346 nests) ranged from 42–69% among colony sites when data were pooled across both years. The DSR of nests was primarily related to colony site, predation risk, height of high tide, and clutch size. Predation and overwash were the principal causes of identifiable nest loss, each accounting for ∼33% of nest failures during the two study years. Because of the challenges of resighting skimmer chicks, we were not able to measure chick survival effectively and therefore accurate measures of productivity remain elusive. High variability in nest success among sites within close proximity to each other (<20 km) suggests factors at local scales such as disturbance, predation, and overwash events strongly influenced nest success of Black Skimmers during these 2 years as opposed to more region-wide stressors such as tropical storms or food availability. Although time-intensive techniques to control predators do exist, management options to limit flooding and overwash are far more limited. Conservation of Black Skimmers in the southeastern USA would benefit from coordinated, multi-state efforts to measure nest and chick survival.