Shoebills (Balaeniceps rex) breed in central-eastern Africa with a world population of only 5,000-8,000 individuals. To provide protection to this threatened species, conservationists need a better understanding about Shoebill foraging and breeding ecology, their habitat use and their distribution. For this study, nest attendance and prey provisioning were recorded with nest cameras for Shoebills in the Bangweulu Wetlands in Zambia in 2012 and 2013. Chick growth and breeding success were monitored at the same time. Parental attendance was constant in the first 40 days of chick rearing, with attending parents only leaving the nest briefly to collect water for cooling the chicks or to collect material to maintain the nest. Attendance decreased as chicks aged, but prey provisioning remained constant throughout the nestling stage at 1.2 deliveries per day. Feeding peaked during the early and late morning. Chick growth rates were as expected given the size of the species, and chicks reached a fledging mass of approximately 5.7 kg. During 2011, breeding success was particularly low (20%, n = 10 nests) due to high levels of human disturbance, with chicks being removed from nests. Parents fledged 0.89 chicks per nest (n = 11 nests) when nests were actively protected from human disturbance and theft in 2012–2013. These findings could be useful for formulating guidelines for sustainable tourism to minimize disturbance and optimize breeding success in Shoebill populations.

Least (Calidris minutilla, n = 110) and Western (Calidris mauri, n = 37) sandpipers collected in Cuban wetlands were sexed by gonadal examination on dissection and used to assess the robustness of two morphometric methods commonly used to assign sex in shorebirds. Discriminant function analyses were performed and then tested by jackknife validation. The best discriminant function for Least Sandpiper included culmen and wing lengths and correctly classified 91% of the birds. Using culmen length, the discriminant function correctly sexed 97% of the Western Sandpiper. Sex ratio and morphometric estimates obtained through sexing Least and Western sandpipers by discriminant functions were not significantly different from the population sexed by gonadal examination on dissection. The range of the bill lengths used for sex determination of Least and Western sandpipers were then assessed by fitting the known-sex data. Classification accuracy of the bill length method was high for Western Sandpiper (95%), but was imprecise (44%) and female biased for Least Sandpiper. Consequently, a female biased sex ratio and under-estimation of male culmen length occurred for Least, but not Western, sandpipers classified by the bill length method. The findings suggest that sex determination based on the single measurement of culmen length is only accurate for Western Sandpiper, a species with high sexual size dimorphism. Linear measurements are also important for sex assignment in Least Sandpiper, but only using a discriminant function analysis approach.

The Changtang Plateau is located in the northern part of Tibet in western China, with the most numerous, high altitude lake complexes in the world. High altitude lakes (n = 48) were visited from July to August, 2008, to investigate the summer abundance and distribution of waterbirds. A total of 43,143 individuals of 49 waterbird species were recorded during our survey. Among them, the most abundant were Bar-headed Goose (Anser indicus), followed by Brown-headed Gull (Larus brunnicephalus), Ruddy Shelduck (Tadorna ferruginea) and Great Black-headed Gull (L. ichthyaetus). These four species comprised 81.2% of all the waterbirds counted. A total of 12,796 Bar-headed Geese were counted at 39 lakes and comprised 29.6% of total birds counted. The lakes with greatest number of individuals were Dong, Rebang, Kunzhong, Yaduo, and Yueqia; the lakes with greatest species richness were Bangong, Dangreyong, Aiyong, Yaduo, and Zharinanmu, while the lakes with greatest bird species diversity were Dangreyong, Bangong, Kunzhong, and Aiyong. In addition, a total of 514 Black-necked Cranes (Grus nigicollis) were counted at 39 lakes, including 326 individuals in Nagqu Prefecture and 188 in Aili Prefecture. There were significant differences between the waterbird species, among the different salinities of the lakes and with the area of the lakes. The principal long-term threat to lakes in the Changtang region is wetland degradation, primarily from mineral exploitation.

The influence of both environmental conditions and social cues on the distance flown to foraging sites was examined for breeding Wood Storks (Mycteria americana) in the Florida Everglades, USA. Adult Wood Storks (n= 73) were followed in a small plane from their nesting colony to their foraging locations during the time when adult Wood Storks were incubating and feeding chicks. On average, foraging sites were close to the nesting colony (mean = 9.6 km ± 1.1), and in shallow water (mean = 9.9 cm ± 0.7) that was receding at a moderate rate (-0.36 cm/day ± 0.13). Wood Storks landed at foraging sites already occupied by other white wading birds 99% of the time, with a mean flock size of 64 ± 14 birds. Model selection identified flock size and water recession rate as the most important variables that influenced Wood Stork foraging flight distances. Distances flown to foraging sites increased with increasing flock sizes and decreased with increasing recession rates (increasing by 39% and decreasing by 18% across the observed range of data, respectively) while accounting for colony location and water depths. These findings are particularly important because they demonstrate that both social and environmental factors play critical roles in the foraging site selection process Wood Storks use during the breeding season. Further, these results in part can be linked to management activities because at least in the case of water recession rates, managers can actively influence recession rates across much of the Everglades landscape.

Darkness comprises more than half of each 24-hr cycle during winter in California's Sacramento Valley, but no studies have assessed nocturnal habitat use by wintering shorebirds at this inland site. From February to May 2013, the day and night habitat associations of radio-tagged Dunlin (Calidris alpina) were compared between post-harvest flooded rice fields and managed freshwater wetlands in the Sacramento Valley. Dunlin had decreasing associations with rice during both day and night from February to April. Dunlin exclusively used rice at night until 25 March, when they shifted to wetlands. During the day, Dunlin were regularly associated with both rice and wetlands until 4 March, and they exclusively used wetlands beginning 25 March. Diel movements by individual Dunlin revealed that birds using rice during the day also used rice during the subsequent night. Our findings suggest that flooded rice, when available, may be more suitable as nocturnal habitat than managed wetlands, and the removal of water from rice fields in February and March causes Dunlin to either use wetlands exclusively or leave the area. Conservation of Dunlin, and likely other migratory shorebirds, may be enhanced by managing the agriculture-wetland mosaic in the Sacramento Valley to ensure that an adequate amount of shallow-water habitats remain during March and April, prior to spring migration.

The global decline in natural wetland cover has enhanced the importance of artificial wetlands, such as rice fields, as waterbird habitats. In this study, relationships of waterbird assemblages, in terms of abundance, diversity and spatial distribution to their invertebrate prey, were investigated across rice paddy fields at various growth stages in western Kenya. Waterbirds were first grouped as large or small waders and prey items as aquatic or non-aquatic. Waterbird assemblage patterns were then tested against prey abundance across three rice growth stages. Overall, waterbirds were most abundant in the middle stages of rice growth (F_2,732 = 3.304, P = 0.041). The most common large waterbirds were in the Ardeidae and Threskiornithidae families, while the most common and abundant small waterbirds were in the Charadriidae and Scolopacidae families. Most small waterbirds were present in the early rice growth stages, while most large waterbirds were present in the middle stages of rice growth. Species diversity differed significantly by rice growth stage among the large but not the small waterbirds (F_2,52= 4.505, P = 0.025). Abundance of small waterbirds was affected more by diversity than by abundance of their prey (R = 0.771, P = 0.034), suggesting a selective feeding strategy that may be driven by frequent mobility or density-dependent dispersal pressures during flooded-field phases. Conversely, large waterbirds were more abundant in more prey-dense areas regardless of prey diversity (R = 0.886, P = 0.024), reflecting a more opportunistic feeding strategy, exploiting both flooded and dry field stages. This strategy explained the wider spatial distribution of large waterbirds. Because of their wide selection of prey type, large waterbirds potentially play a greater role in controlling ground-level rice pests across all rice growth stages. Field management options that favor presence of large waterbirds may enhance this ecological role of natural rice pest control.

Reduced nest survival has been suggested as a primary cause for the decline of Snowy Plover (Charadrius nivosus) populations. The fates of Snowy Plover nests (n = 589) were determined from five locations at the Great Salt Lake in Utah during the 2003, 2005–2010 and 2012 breeding seasons. A five-stage hierarchical modeling procedure was used, and five competing models (ΔAIC_c < 2) that best described variation in nest survival were identified. These competing models included the influences of study site and year with a quadratic time trend and covariates quantifying nest age, temperature, precipitation, distance to water control structures (dikes), and nesting substrate (barren mudflat, vegetation patches, or conspicuous objects). Among unsuccessful nests (45.6%; n = 277), the most common cause of failure was predation (72.9%), followed by weather and abandonment (10.5% and 10.1%, respectively). Daily nest survival rates ranged from 0.89 to 0.97 and varied annually and across sites. Nests located on barren flats had lower daily nest survival than those located in vegetated patches or near conspicuous objects. Proximity to dikes influenced nest survival as nests within 100 m had lower daily survival rates than nests further than 100 m from dikes. The population of Snowy Plovers on the Great Salt Lake contributes substantially to an overall imperiled North American population. Managers should consider measures to reduce the attractiveness of dikes as nesting habitat to increase nest survival rates for Snowy Plover.

Shorebird assemblage composition and habitat-use patterns were characterized at Punta Rasa during the austral summer, autumn and winter. Compared to other sites within the region, this area showed high species richness, reflected by a total of 22 species recorded within a relatively short time frame. Differences in assemblage structure were driven by the use of estuarine mudflats and oceanic sandy beaches as feeding habitats. During low tide, more species used estuarine environments, achieving the highest total densities. Abundance patterns and assemblage composition also changed seasonally. Maximum total abundance occurred during the austral summer, and minimum total abundance during the austral winter. During the austral summer, the assemblage was dominated by Nearctic migrants such as American Golden-Plover (Pluvialis dominica), Hudsonian Godwit (Limosa haemastica) and White-rumped Sandpiper (Calidris fuscicollis). In addition, Two-banded Plover (Charadrius falklandicus) and American Oystercatcher (Haematopus palliatus) were abundant during the austral autumn. The Red Knot (Calidris canutus), a shorebird that dominated the austral autumn assemblage 25 years ago, was recorded in relatively small numbers during this study, probably reflecting the global population trend of a subspecies of the Red Knot (C. c. rufa) in the past two decades. During the austral winter, resident birds largely dominated the assemblage. However, it is noteworthy that some individuals of nine Nearctic migrant species remained in the area. In the case of the endangered Red Knot, Punta Rasa is, along with Lagoa do Peixe in Brazil, one of the sites in South America with the highest known abundances during the austral winter.

Predicted sea-level rise and increases in the frequency and magnitude of storm surges are potential threats to waterbird nests and associated breeding habitat on low-lying landforms, such as barrier islands. Sea-level rise in Northumberland Strait of eastern Canada, predicted to rise by at least 0.50–0.60 m by 2100, could permanently flood large tracts of barrier island habitat. Potential impacts of higher sea levels on breeding habitat of Red-breasted Mergansers (Mergus serrator) were studied on three barrier islands at Kouchibouguac National Park, New Brunswick, Canada. Objectives of the study were to: 1) identify the range of dates for which nests (n = 189) were active and thus vulnerable to flooding; 2) determine elevation and distance to water for each nest; 3) examine whether birds selected nest sites that were relatively elevated and far from water; and 4) estimate the proportion of nests that could be flooded under four plausible sea-level rise and storm surge scenarios. Peak nesting occurred during mid-June to mid-July. Red-breasted Mergansers generally sought elevated regions with beach grasses for nest placement. Nearly 50% of nests were < 2 m above mean sea level. Nest elevations were greater than a conservative estimate of sea-level rise of 0.60 m. However, ≥ 50% of these nests are predicted to be flooded during a high spring tide if sea levels are 0.60 m greater, and these impacts would be exacerbated when phased with a storm surge. A predicted surge of 2.55 m above mean sea level would inundate 90% of nests on the islands. Results indicate that predicted sea-level rise for Northumberland Strait over the next century threatens the habitat and survival of waterbird nests on barrier islands, particularly if there is little accretion to the islands during this period. Accordingly, rates of sediment accretion or erosion on the Tern Islands should be monitored closely as sea levels continue to rise.

Information on Nearctic shorebirds is scarce for inland South America. This work presents information on abundance and habitat use of the species that inhabit water bodies in the highlands of western Santa Cruz province, Argentina. Surveys were conducted during four austral summers (January to March) from 2010 to 2013, with annual data collected at 378 lakes. Results indicate that species distribution varies from year to year. The most abundant species was Baird's Sandpiper (Calidris bairdii). Habitat modeling showed that this species favors ‘depression’ type lakes and that individuals do not distribute uniformly across the area, with higher yearly abundance at Strobel Plateau and the plateaus of the ‘Austral complex’. Size of the water body is positively related to abundance of White-rumped Sandpiper (C. fuscicollis) and Wilson's Phalarope (Phalaropus tricolor). Results show that these highlands are sites of interest for the conservation of migratory shorebirds.

Although several studies have reported basic information about the size of Kelp Gull (Larus dominicarius) eggs, no attention has been paid to the comparison of patterns of intra-clutch variation at different breeding sites. Here, the variation in egg size of Kelp Gulls at two colonies from Patagonia, Argentina, was analyzed. The objectives were to characterize egg size variation in Kelp Gulls breeding at a recently established colony in Punta Loma that primarily relies on natural prey; and to evaluate if patterns of intra-clutch variation in that colony differ from those at Vernaci Sudoeste Island, a larger and well-established colony with access to supplementary food in the form of fishery waste. In two-egg clutches, first-eggs were larger than second-eggs. Neither average egg size nor intra-clutch patterns differed between study sites. Also, in two-egg clutches, egg size decreased as date of laying increased, probably due to younger birds laying smaller eggs later in the season. The pattern of intra-clutch variation in three-egg clutches differed between sites. Three-egg clutches at Vernaci Sudoeste Island presented similar sizes for first- and second-eggs and these were larger than third-eggs. This pattern contrasted with the steady decrease in relation to laying order that was observed at Punta Loma. Also, second-and third-eggs from Vernaci Sudoeste Island were larger than corresponding eggs from Punta Loma. Our data suggest that differences in egg size between colonies could be the consequence of enhanced food availability at Vernaci Sudoeste Island in the form of discards generated by trawl fisheries. Future studies to evaluate age of birds and inter-annual environmental stochasticity are needed to elucidate the effect of these factors on egg size variation.

Western (Aechmophorus occidentalis) and Clark's (A. clarkii) grebes are long-lived, migratory waterbirds that are sensitive to human-caused disturbance while nesting. Sampling the age distribution of post-hatch chicks provides a method for estimating the timing of nest initiation without causing disturbance to breeding colonies. The goals of this work were to describe trends in breeding productivity at two of the largest nesting colonies in northern California and illustrate how brood size can be used to evaluate nesting phenology in Aechmophorus grebes. No differences were found in brood size between species. Brood size decreased linearly as nest initiation date increased, showing no differences in the rate of decline among age classes of young. Within seasons, older broods were found to be significantly smaller than younger broods, suggesting that mortality was occurring after hatching thereby reducing the potential number of chicks recruited into the adult population.

The Black Guillemot (Cepphus grylle) is a monomorphic seabird characterized by its muted plumage and bright red feet, which it prominently displays during courtship. Foot color and oxidative stress were analyzed in a Black Guillemot colony at the Bay of Fundy during the 2006 and 2007 breeding seasons. While no relationship between red intensity of feet and carotenoids was uncovered, the level of plasma oxidative damage was negatively correlated with foot color. Additionally, red intensity of male feet was significantly correlated with the red intensity of their mates' feet, suggesting the possibility of assortative mating by foot color in this species. Further experimental work is necessary to determine whether foot color is used in this species as an honest signal to relay information on the ability of an individual to manage oxidative stress.