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Coastal ecosystems are under increasing pressure from human activity, introduced species, sea level rise, and storm activity. Hurricanes are a powerful destructive force, but can also renew coastal habitats. In 2003, Hurricane Isabel altered the barrier islands of North Carolina, flattening dunes and creating sand flats. American Oystercatchers (Haematopus palliatus) are large shorebirds that inhabit the coastal zone throughout the year. Alternative survival models were evaluated for 699 American Oystercatcher nests on North Core Banks and South Core Banks, North Carolina, USA, from 1999–2007. Nest survival on North Core Banks increased from 0.170 (SE = 0.002) to 0.772 (SE = 0.090) after the hurricane, with a carry-over effect lasting 2 years. A simple year effects model described nest survival on South Core Banks. Habitat had no effect on survival except when the overall rate of nest survival was at intermediate levels (0.300–0.600), when nests on open flats survived at a higher rate (0.600; SE = 0.112) than nests in dune habitat (0.243; SE = 0.094). Predator activity declined on North Core Banks after the hurricane and corresponded with an increase in nest survival. Periodic years with elevated nest survival may offset low annual productivity and contribute to the stability of American Oystercatcher populations.
Eared Grebes (Podiceps nigricollis) staging at the Great Salt Lake, Utah, USA, sometimes experience weather-induced downings where many individuals are killed. Downings of Eared Grebes moving south during the fall have been reported for decades; however, spring downings are rare and underrepresented in the literature. On 15 April 2013, 13,500 Eared Grebes flying northward encountered inclement weather, were attracted to lights on Dugway Proving Ground, and downed. This spring downing was documented, and population characteristics were compared with those observed in previous downings. An estimated 38% were killed outright. Rescue efforts promoted the survival of 88% of those not killed on impact. Grebes that were 9–10 months old were, on average, 10% lighter than adults in the same flight, perhaps indicating slow growth or age differences in foraging efficiency. Adults dominated all downings, supporting previous information that adults and young migrate on different schedules. The sex ratio in the North American population appears to be 1:1. Downings occur when Eared Grebes encounter inclement weather and are attracted to lights. Knowledge of the route, migration period, and flight speed of Eared Grebes allows predictions about when and where downings are likely to occur. Reducing the number and intensity of lights on snowy nights in high risk areas may decrease mortality.
The breeding parameters of the Black-faced Ibis (Theristicus melanopis) in pastures of southern Chile between 5 July and 30 November 2014 were evaluated. Thirty active nests were monitored in an area of 31 km2, using a mirror mounted on a 13-m retractable aluminum pole. Each nest was visited once a week. The Black-faced Ibis presented an asynchronous posture period, with a maximum of three egg clutches. The first eggs were laid on 6 August 2014, and the mean incubation period was 28.66 (± 4.41) days. Mean clutch size during the first posture was 2.23 (± 0.73) with a range of one to three eggs per nest. None of the structural parameters of the nesting site evaluated were related to clutch size. The nests were oriented with a mean angle of 218° SW. Hatching of the chicks began on 25 September 2014, and the mean period of parental care lasted 36.67 (± 14.49) days. The apparent hatching success was 0.54, the fledging success was 0.40, and the total breeding cycle success was 0.23 independent young per nest. Predation explained the 56.7% nest loss. Chimango Caracara (Milvago chimango) was the main predator of eggs and chicks. The Mayfield estimator indicated a daily survival probability of 4.4% for the incubation cycle, 26.2% for the fledglings and 11.3% for the total breeding cycle.
Poyang Lake is China's largest freshwater lake in summer and provides important habitat for an internationally significant assemblage of waterbirds in winter. Human-caused alterations to this system threaten to compromise the long-term viability of these bird populations due to the role of water in driving habitat suitability. Little is known, however, about the patch-scale habitat selection strategies of waterbirds within Poyang. Consequently, there is potential for spatial incongruence between protected area boundaries and key habitats given the system's high variability. This study used scan and focal sampling techniques to investigate patch selection by a wintering population of the Eurasian Spoonbill (Platalea leucorodia) within the Sha Hu sub-lake basin of Poyang Lake. Eurasian Spoonbills averaged higher foraging success rates in areas with water depth of 28.1-36.6 cm compared to other areas and preferred to forage in this depth class, as indicated by usage disproportionate to availability (Manly's standardized selection index = 0.817). Defining the patch-scale habitat selection of this indicator species both quantifies the impact of hydrological changes on resource availability and spatially predicts suitable areas for wintering birdlife within a dynamic environment.
The ecology of stork colonies in southern Asia are very poorly understood. Factors affecting provisioning times of adults were evaluated at nests of two stork species, the Asian Openbill (Anastomus oscitans) and the Lesser Adjutant (Leptoptilos javanicus), in lowland Nepal, where the landscape is dominated by multi-cropped agriculture fields. Analyses focused on understanding if provisioning times were influenced more due to colony-level variables, wetlands around colonies, or season. Using generalized additive mixed models and the information-theoretic approach, colony-level variables (brood size and chick age) showed non-trivial associations with provisioning times (substantially better than the null model). Univariate models with colony size and wetlands had poor support (worse than the null model). Season, which represented the changing cropping patterns, rainfall, and wetness on the landscape, was the most important variable for both species. The combination of season and wetlands was very important for provisioning Asian Openbills whose chicks fledged during the monsoon (July-October), but not for Lesser Adjutants whose chicks fledged in the drier winter months (November-February). Results strongly suggest that changing cropping patterns to a drier monsoonal crop, or reductions in wetland extents, will be detrimental to storks in Nepal.
The highly urbanized San Francisco Bay Estuary, California, USA, is currently undergoing large-scale habitat restoration, and several thousand hectares of former salt evaporation ponds are being converted to tidal marsh. To identify potential effects of this habitat restoration on breeding waterbirds, habitat selection of radiotagged Forster's Terns (Sterna forsteri) was examined at multiple spatial scales during the pre-breeding and breeding seasons of 2005 and 2006. At each spatial scale, habitat selection ratios were calculated by season, year, and sex. Forster's Terns selected salt pond habitats at most spatial scales and demonstrated the importance of salt ponds for foraging and roosting. Salinity influenced the types of salt pond habitats that were selected. Specifically, Forster's Terns strongly selected lower salinity salt ponds (0.5–30 g/L) and generally avoided higher salinity salt ponds (≥ 31 g/L). Forster's Terns typically used tidal marsh and managed marsh habitats in proportion to their availability, avoided upland and tidal flat habitats, and strongly avoided open bay habitats. Salt ponds provide important habitat for breeding waterbirds, and restoration efforts to convert former salt ponds to tidal marsh may reduce the availability of preferred breeding and foraging areas.
The effect of aquatic birds on nutrient cycling and energy flow was investigated in two soda pans, one turbid and the other colored, with different physical and chemical characteristics. Primary plankton production and respiration were measured together with an estimation of waterbird carbon, nitrogen and phosphorus loading during 2014. Both pans were hypertrophic and showed net heterotrophy. The nutrient loading of the birds in the turbid pan was approximately five times higher (C: 758 kg/ha/year, N: 122 kg/ha/year, P: 20 kg/ha/year) than in the colored pan, with significant guanotrophication. Despite the high chlorophyll a concentrations (turbid: 752 µg/l and colored: 369 µg/l, on average), the annual surface-related planktonic production was relatively low (turbid: 64 mg C/m2/year and colored: 23 mg C/m2/year), by contrast, respiration was similar in the two pans (turbid: 75 C/m2/year and colored: 78 mg C/m2/year). Nutrient loading showed a significant positive correlation with total and soluble reactive phosphorus, chlorophyll a and gross planktonic production, supporting the conclusion that the waterbirds significantly affected primary production. By contrast, there was no significant correlation between the nutrient loading and planktonic respiration. The low production and respiration ratio (Pro/Res) in the colored pan was presumably caused by a high dissolved organic carbon concentration (polyhumic). A possible explanation for the difference of Pro/Res between the turbid and colored pans is variation in the decomposition of the bird excrement and surrounding macrophytes.
The biology of the Common Tern (Sterna hirundo) has been studied on several continents, but information from central Asia is limited. Colony characteristics and nest site selection of Common Terns were studied in the desert and steppe of Mongolia to determine factors that influence their choices. Common Terns nested in marshy areas around small ponds, on sand bars adjacent to a lake in the Gobi, and on small islands in a water treatment plant in the steppe of Ulaanbaatar. In the Gobi, they nested with Pied Avocets (Recurvirostra avosetta) that defended the colony site, while the terns left. Common Terns selected colony sites surrounded by water and muck/ mud, and nest sites with good visibility. Their choice of colony and nest sites seemed to be a compromise between avoiding flooding, avoiding nest trampling by livestock, and finding any safe nesting place to avoid terrestrial predators.
Patterns of louse infestation in waterbirds deserve attention due to potential impacts on host populations. Red-necked Grebes (Podiceps grisegena) were visually examined for the presence of amblyceran chewing lice during the 2000–2015 breeding seasons in eastern Poland. Only one species of lice (Pseudomenopon dolium) was recorded. Amblyceran prevalence was low; four young birds (2.7%) were found infested out of 147 banded individuals (66 adults and 81 chicks). However, all infested Red-necked Grebes bore heavy parasite loads. Negative consequences of infestation for physiological condition were indicated by low hemoglobin and total protein values when compared with same-age non-infested birds. The low infestation rate can be related to the biology of the host (a diving species undergoing molt at sea, solitary breeder) and the apparent high pathogenicity of P. dolium, which left numerous holes in feathers and bleeding bites in all parasitized birds.
Fifteen polymorphic microsatellite loci were isolated from the endangered Barau's Petrel (Pterodroma baraui), endemic to Réunion Island, Indian Ocean, France, facilitating population studies for conservation. In 148 samples from two colonies, the total number of alleles per loci ranged from three to eight, observed heterozygosity ranged between 0.11 and 0.86, and null allele frequency ranged between 0.000 and 0.093. An observed similarity in annealing temperatures across loci and the wide range of fragment sizes facilitated polymerase chain reaction multiplexing and rapid multilocus genotyping. These results will enable further investigation into the genetic diversity, effective population size, and small-scale geographical relationships among populations of this endangered species, encouraging additional conservation initiatives.
Avian research that involves potential disturbance to the study species may have unintended fitness consequences and could lead to biases in measurements of interest. The effects of band resighting on the behavior of mixed-species flocks of staging waterbirds were evaluated against recreational pedestrian activity that was expected to cause flushing. We found a model with additive effects of distance (near, 0-50 m, or far, 50-200 m) and disturbance type (researcher or pedestrian) best explained flock behaviors. The proportion of staging flocks that flushed in response to pedestrians was greatest when pedestrians were within 50 m of the flock. Virtually no flushes were observed in response to researchers, regardless of distance. These results could assist in alleviating concerns that accepted protocols used for intensive band resighting studies on staging seabirds of special conservation status, such as Roseate (Sterna dougallii) and Common (S. hirundo) terns, may have adverse effects. Our framework could be used by others to test the effects of similar research on sensitive species.
To better understand how wading birds select among microhabitats that show spatial heterogeneity, a concrete weir located at the terminus of the Little Arkansas River in Wichita, Kansas, USA, was divided into patches based on water depth. Black-crowned Night-Herons (Nycticorax nycticorax; n = 396), Great Egrets (Ardea alba; n = 54), Snowy Egrets (Egretta thula; n = 36), and Great Blue Herons (Adrea herodias; n = 30) were observed for 60 hr from 10 June-29 July 2015. The total number of individuals was recorded, as was species-specific patch use, feeding activity, and aggression. Only time of day and water depth predicted the number of birds at the weir (R2 = 0.52). Wading bird species differed in capture efficiency, mean prey size, and patch use. Great Blue Herons and Black-crowned Night-Herons mainly captured larger fish below the weir, Snowy Egrets captured mostly smaller fish along the weir edges, and Great Egrets captured both large and small fish. Mean fish length differed by patch and ranged from 2.8–11.9 cm. Total aggression correlated with the number of large fish caught but not with total fish; per capita aggression correlated with the number of birds. Electrofishing showed a non-uniform spatial distribution of fish numbers and biomass. Species-specific foraging patterns reflected patterns of water depth, fish distribution, and aggression.
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