Female Northern Pintails (Anas acuta) were sampled in California's three main Central Valley wintering regions (Sacramento Valley, Suisun Marsh, San Joaquin Valley) during September–October before most regional movements occur and microsatellite and mitochondrial DNA were analyzed to examine population structure and relatedness. Despite reportedly high rates of early-fall pairing and regional fidelity, both sets of markers indicated that there was little overall genetic structuring by region. Pintails from Suisun Marsh did exhibit higher relatedness among individuals and capture groups than in the Sacramento or San Joaquin Valleys, likely reflecting a sample comprised of a greater proportion of local breeders. The lack of genetic structuring among regions indicates that a high degree of movement and interchange occurs among pintails wintering in the Central Valley. Thus, although maintaining the existing distribution of pintails among Central Valley regions is important for other reasons, it does not appear to be critical to retain current patterns of population genetic variation. Because of potential lack of independence among highly related study individuals, researchers should consider regional differences in relatedness when designing sampling schemes and interpreting research findings.

The use of tissue stable isotope values to track animal movements is well-established but independent tests of existing models and assignment accuracy at coarse spatial scales and for non-model species are rare. Assignment error associated with an existing model for distinguishing origins of North American Mallards (Anas platyrhynchos) on the basis of feather δ³⁴S, δD, δ¹⁵N and δ¹³C values was evaluated. Prior information about regional movements reported in Mallard mark-recapture studies was accounted for, and new models generated and applied to independent data obtained from flightless, juvenile Mallard and Lesser Scaup (Aythya affinis). Assignment error of an existing model was reduced from 14 to 8% by incorporating prior information about mallard movement rates between Pacific and Mid-continent Flyways (range 0 to < 1%) in Flyway-specific models. The revised Mid-continent model correctly assigned 86% of 70 flightless hatch-year Mallards captured at breeding areas in central North America during 2005 to origin. Assignment accuracy ranged from 76 to 91% over five 1° latitude increments where Boreal Forest and Prairie regions were increasingly separated from a focal Aspen Parkland region; here, separating Boreal Forest and Prairie regions from the Aspen Parkland by 4° latitude provided the highest relative assignment success rates among all three regions. Estimated origins of known-source scaup were accurate (14 of 16) for birds with feathers grown in Aspen Parkland but not (0 of 5) for those grown in the Canadian North-western Boreal Forest. The results support the use of multiple feather-isotopes for assigning natal origins of birds at broad geographic scales but evaluation of factors affecting species-specific isotope differences is required for application of existing models to other species.

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 that offspring winter closer to the male rather than the female parent (P-value = 0.03), and adult males and females appear to exhibit latitudinal segregation (P-value < 0.001). Females reach the winter grounds before males, arriving in July and staying through April (∼9 months) or 75% of the annual cycle. The study is the first to identify winter distribution for the Great Lakes Piping Plover population. The significant proportion of the annual cycle spent on the wintering grounds emphasizes the importance of habitat protection during the non-breeding season for this federally-listed population.

Forager (predator) abundance may mediate feeding rates in wading birds. Yet, when modeled, feeding rates are typically derived from the purely prey-dependent Holling Type II (HoII) functional response model. Estimates of feeding rates are necessary to evaluate wading bird foraging strategies and their role in food webs; thus, models that incorporate predator dependence warrant consideration. Here, data collected in a mangrove swamp in Puerto Rico in 1994 were reanalyzed, reporting feeding rates for mixed-species flocks after comparing fits of the HoII model, as used in the original work, to the Beddington-DeAngelis (BD) and Crowley-Martin (CM) predator-dependent models. Model CM received most support (AIC_c w_i = 0.44), but models BD and HoII were plausible alternatives (ΔAIC_c ≤ 2). Results suggested that feeding rates were constrained by predator abundance. Reductions in rates were attributed to interference, which was consistent with the independently observed increase in aggression as flock size increased (P < 0.05). Substantial discrepancies between the CM and HoII models were possible depending on flock sizes used to model feeding rates. However, inferences derived from the HoII model, as used in the original work, were sound. While Holling's Type II and other purely prey-dependent models have fostered advances in wading bird foraging ecology, evaluating models that incorporate predator dependence could lead to a more adequate description of data and processes of interest. The mechanistic bases used to derive models used here lead to biologically interpretable results and advance understanding of wading bird foraging ecology.

Resource partitioning in three sympatric stork species: Black-necked Stork (Ephippiorhynchus asiaticus) Painted Stork (Mycteria leucocephala) and Asian Openbill (Anastomus oscitans) ) was studied in the Keoladeo National Park, India from October 1994 to May 1997. Little is known about their feeding success in variable water depths and habitat use. The Black-necked Stork, a solitary generalist forager, uses tactile and visual methods with a high proportion offish in the diet. The Painted Stork and Asian Openbill forage in groups of two to 100. Both Painted and Asian Openbill Storks are specialists and tactile foragers, with the former preferring fish and the latter snails (Pila spp.). Differences in prey composition were mainly due to difference in feeding behavior and water level at foraging sites. Peck rate, steps and success rate varied significantly among the three species and water level influenced feeding success. The three stork species showed variations in foraging parameters in relation to fine-scale habitat use. All stork species showed preferences for foraging habitat that differed with respect to water level, vegetation community structure and the presence of prey species. The fishing depth component of resource segregation, as described in many wading bird communities has played a major role in determining feeding success and reducing niche overlap. The findings have application to foraging habitat management and the conservation of stork species.

Stable-isotope analysis of whole blood was used to examine the feeding of adults and chicks of five seabirds (Wedge-tailed Puffinus pacificus and Christmas Shearwaters P. nativitatus, Bonin Pterodroma hypoleuca and Bulwer's Petrels Bulweria bulwerii and Tristram's Storm-petrel Oceanodroma tristrami) in the northwestern Hawaiian Islands. The goal was to compare community foraging patterns as determined by stable-isotope analysis with traditional studies conducted in the early 1980s. Furthermore, chick-rearing Procellariiformes have been hypothesized to practice a bimodal food-provisioning strategy, a behavior yet to be documented in any of the northwestern Hawaiian Islands species outside the albatrosses. Except for Christmas Shearwaters, adults and chicks had significantly different isotope ratios, suggesting differential self- and chick-provisioning by adults. Wedge-tailed Shearwaters foraged opportunistically for themselves, while providing prey of higher trophic position to their chicks. Bulwer's Petrel and Tristram's Storm-petrel adults likely brought prey of more uniform trophic position to their chicks, while relying on more permanent prey patches differing in composition for themselves during the breeding season. Results suggested little overlap in stable-isotope ratios among species and were likely a result of behavioral and morphological differences in feeding.

Time activity budgets, foraging habitat quality and behavior of Semipalmated Plovers (Charadrius semipalmatus) were examined during three non-breeding seasons in a large estuarine system in southeastern Georgia, USA. Among the foraging sites available to shorebirds at each tidal stage, non-breeding plovers tracked those with the greatest biomass and density of invertebrate prey. Prey biomass differed according to tidal conditions but was strongly predicted by the salinity, organic content and particle sizes of the sediments. Foraging rates (pecks/ min) and densities (birds/ha) of plovers were both predicted by invertebrate density and biomass. Foraging rates correlated significantly with the rate of defecations, indicating that peck rates were related to intake rates. Foraging rates reached an asymptote of 25 pecks per minute, suggesting an upper limit to the rate of capture unconstrained by digestive bottlenecks. While available, nearly all plovers foraged when on mudflat habitats, while about 33% foraged on salt marsh habitats and 12% foraged on beaches. There was no effect of density of foraging birds on their rate of foraging at mudflats, suggesting that birds were not experiencing intra-specific competition at this productive site.

Diets of breeding Imperial Cormorants Phalacrocorax atriceps were studied at two breeding colonies, Islas Blancas and Isla Arce, located approximately 30 km apart in an area subject to increasing fishing pressure off Central Patagonia, Argentina. The goal was to assess differences between locations and diet variation among stages of the breeding cycle. Pellet casts (403 and 358 pellets per colony, respectively) were collected from November 2002 to February 2003. Analyses of the pellets revealed that Imperial Cormorants at Islas Blancas and Isla Arce fed on at least 25 and 23 prey types, respectively. Fish showed the highest frequency of occurrence at both colonies (> 70%), followed by crustaceans and molluscs. Of the fish prey, Merluccius hubbsi (22–71%), Engranlis anchoita (16–51%) and Raneya brasiliensis (5–48%) showed the highest frequencies of occurrence, depending on the colony and breeding stage. At Islas Blancas, the consumption of fish and crustaceans was similar among breeding stages (incubation, young chicks and old chicks), while it was significantly different at Isla Arce. Overall contribution by frequency of occurrence showed that M. hubbsi was the most frequent prey at Islas Blancas (58%), and E. anchoita and Pleoticus muelleri were more frequent at Isla Arce (48 and 45%, respectively). Also, overall contribution by mass of the main fish prey indicated differences between colonies. Given the commercial value of the main prey species, cormorant feeding requirements and spatial ecological needs should be included as considerations in coastal fisheries management and future development.

A discriminant function analysis (DFA) model was developed with DNA sex verification so that external morphology could be used to sex 203 adult California Gulls (Larus californicus) in San Francisco Bay (SFB). The best model was 97% accurate and included head-to-bill length, culmen depth at the gonys, and wing length. Using an iterative process, the model was simplified to a single measurement (head-to-bill length) that still assigned sex correctly 94% of the time. A previous California Gull sex determination model developed for a population in Wyoming was then assessed by fitting SFB California Gull measurement data to the Wyoming model; this new model failed to converge on the same measurements as those originally used by the Wyoming model. Results from the SFB discriminant function model were compared to the Wyoming model results (by using SFB data with the Wyoming model); the SFB model was 7% more accurate for SFB California gulls. The simplified DFA model (head-to-bill length only) provided highly accurate results (94%) and minimized the measurements and time required to accurately sex California Gulls.

Archived Great Blue Heron (Ardea herodias) eggs (N = 16) collected in 1993 from three colonies on the Mississippi River in Minnesota were analyzed in 2007 for perfluorinated compounds (PFCs) and polybrominated diphenyl ethers (PBDEs). One of the three colonies, Pig's Eye, was located near a presumed source of PFCs. Based on a multivariate analysis, the pattern of nine PFC concentrations differed significantly between Pig's Eye and the upriver (P = 0.002) and downriver (P = 0.02) colonies; but not between the upriver and downriver colonies (P = 0.25). Mean concentrations of perfluorooctane sulfonate (PFOS), a major PFC compound, were significantly higher at the Pig's Eye colony (geometric mean = 940 ng/g wet weight) than at upriver (60 ng/g wet weight) and downriver (131 ng/g wet weight) colonies. Perfluorooctane sulfonate concentrations from the Pig's Eye colony are among the highest reported in bird eggs. Concentrations of PFOS in Great Blue Heron eggs from Pig's Eye were well below the toxicity thresholds estimated for Bobwhite Quail (Colinus virginianus) and Mallards (Anas platyrhynchos), but within the toxicity threshold estimated for White Leghorn Chickens (Gallus domesticus). The pattern of six PBDE congener concentrations did not differ among the three colonies (P = 0.08). Total PBDE concentrations, however, were significantly greater (P = 0.03) at Pig's Eye (geometric mean = 142 ng/g wet weight) than the upriver colony (13 ng/g wet weight). Polybrominated diphenyl ether concentrations in two of six Great Blue Heron eggs from the Pig's Eye colony were within levels associated with altered reproductive behavior in American Kestrels (Falco sparverius).

Horseshoe Crab (Limulus polyphemus) eggs are an important shorebird food during the Delaware Bay spring stopover, and shorebird management plans aim to increase and monitor this resource. If shorebirds focus their foraging on Horseshoe Crab nesting depressions they may find richer food supplies than if they forage randomly on the beach. The amount of shorebird sign in quadrats centered on Horseshoe Crab nest depressions was compared with the amount of sign in paired beach areas with no Horseshoe Crab nests. Horseshoe Crab nest depressions had more pecks, probes, digit marks, Ruddy Turnstone excavations, Horseshoe Crab eggs and a greater coverage by shorebird sign than paired beach plots with no Horseshoe Crab nests. Foraging disproportionately within Horseshoe Crab nesting depressions may facilitate the rapid mass gain needed to prepare shorebirds for their flight to the breeding grounds. Horseshoe crab egg monitoring currently estimates mean egg abundance per beach. However, birds are able to find patches with high egg densities even when foraging on beaches with lower average densities.

With the exception of western Europe, little is known about foraging by White Storks on rubbish dumps. Information is presented on this phenomenon along the migration routes and wintering grounds of the White Stork. White Stork foraging on rubbish dumps is a common behavior in northern Africa and the Middle East and appears related to the wintering of European White Storks in new areas closer to their breeding grounds. South Africa, where a local breeding population has established, is another region where foraging on rubbish dumps has been observed. The development of rubbish dumps may have major consequences for the future ecology of White Stork.

The identification of predators of aquatic birds can be difficult. The Common Snapping Turtle (Chelydra serpentine) is considered a major predator of waterfowl and other aquatic birds, but the evidence for this reputation is based largely on circumstantial or indirect evidence rather than direct observations. Herein, the first documented observations of a snapping turtle attacking and killing an adult Western Grebe (Aechmophorus occidentalis) are described.

The Hooded Crane (Grus monacha) is a globally threatened waterbird. From October 2007 to April 2008, the time-activity budgets of the cranes were recorded in Shengjin Lake, the main wintering area for the crane in China. Instantaneous scan sampling was used to observe the behavior of the wintering cranes. Foraging and alerting were the most frequent diurnal behaviors, with average diurnal time-activity budgets of 60.4% and 15.5%, respectively. The time budgets for diurnal behaviors were significantly different from 07:00 to 18:00 for all behavior categories except for alerting and social behaviors. Over the winter period, the time budget for foraging increased from 56.2% in the early stages to 65.7% in the late stage. However, the percentage of time spent alerting decreased from 20.7% to 10.4% as winter progressed. In family groups, adults usually spent more time on maintenance, alerting, locomotion and social behaviors, and less time on foraging and resting than juveniles, in all wintering stages. In the early and middle of winter, the foraging time budget of adults was significantly different from that of juveniles, while at the late stage it was not. The alerting time budget of adults was significantly different from that of juveniles in the early and middle stages of winter, but the difference were less statistically significance in the late stage. The results imply that wintering cranes in Shengjin Lake exhibit different behavioral patterns over the different winter stages to adapt to the degraded and disturbed environment, and parental care of offspring should increase juvenile survival.

Post-juvenile molt of Common Snipe was investigated during 2004-05 at the Jeziorsko reservoir, central Poland. Body mass and mass of fat stores were dependent on the stage of post-juvenile molt. The body mass increased prior to the commencement of molt, but during the intensive stage of the process it decreased and returned to the previous level. Fat-free body mass increased during molt, which may be attributed to increased protein synthesis or the higher water content of growing feathers. Fat stores were similar in snipe before and in the initial stage of molt; however, they decreased significantly during the transition to the intensive stage of the process. In total, snipe lost approximately 57% of the mass of fat loads over the course of molt (4.9% of lean body mass). Being a highly energetic constraint, post-juvenile molt is suggested to affect certain life history traits of Common Snipe such as the length of the staging periods during the autumn migratory period.