Abdim’s Storks Ciconia abdimii were studied in a post-breeding staging area dominated by Sahelian grasslands in southeastern Niger. In late September 2003, a total of 5,763 birds was recorded on systematic transect counts. The estimated density was 5.66 per km², equivalent to a total of c. 17,000 Abdim’s Stork within the utilized area of 3,000 km². A high percentage of juveniles in the flocks in late August, when the Nigerien breeding population is still at their nests, indicate a southern origin of the birds. The storks probably make northward post-breeding movements into the Sahel to feed on locally abundant food supplies, first of all Senegalese Grasshopper Oedaleus senegalensis, the dominant grasshopper species in the area. The mean density of Oedaleus in late September 2003 was 11.2 per m² (6.7 g fresh weight/m²). Storks feeding on grasshoppers made on average 5.6 successful pecks per min during their first h of daily feeding, enabling them to fulfil 95% of their daily energy requirements within one h. In 2005, Oedaleus densities were only 5.1 per m² (2.8 g fresh weight/m²). Foraging storks made on average 2.5 and 1.9 successful pecks per min during the first and second h of daily feeding, respectively, and even two h of active foraging allowed them to fulfil only 70-75% of their daily needs. As a probable consequence, the storks left the area earlier than in 2003. Flocks of Abdim’s Stork are able to significantly reduce grasshopper densities in frequently used areas, but their impact on Oedaleus numbers within the 3,000 km² utilized area as a whole is probably negligible. However, the impact of the storks should not be viewed in isolation.

We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ¹³C and δ¹⁵N analysis, based on a study of Barau’s Petrels (Pterodroma baraui) and White-tailed Tropicbirds (Phaethon lepturus). Samples were analyzed for stable isotopes before and after lipid removal. Lipid-free muscle and liver were significantly enriched in ¹³C compared to those containing lipids (0.52‰ and 0.61‰ mean differences in δ¹³C respectively) implying that lipids should be extracted from these tissues to avoid effects of uncontrolled differential lipid content. However lipid extraction also slightly increased muscle δ¹⁵N values in tropicbirds. Researchers should thus run samples separately for δ¹³C and δ¹⁵N analysis, extracting lipids only in aliquots in which δ¹³C is measured, or apply arithmetic δ¹³C normalization methods on non lipid-extracted samples. Predictive models developed from our data, inferring δ¹³C values of lipid-extracted material from δ¹³C values and C:N ratios of non lipid-extracted material are presented and compared to five normalization methods taken from literature. Our models showed the best prediction efficiencies followed by that developed by McConnaughey and McRoy (1979). In feathers, no difference in stable isotopic measurements were noted between aliquots treated with sodium hydroxide or 2:1 chloroform:methanol. Both protocols seem suitable for preparing feather samples for isotopic analysis.

I examined the food exploitation patterns of three day herons, Great Egret (Ardea alba), Snowy Egret (Egretta thula), Tricolored Heron (E. tricolor) and a nocturnal species, the Black-crowned Night-Heron (Nycticorax nycticorax) that nested together in an estuarine colony. Types and sizes of prey were determined by analyzing the food of nestlings. These data were evaluated in light of relative abundance of prey, which was based on fish collected in nearby tidal creeks. The majority of food items (43%) taken by the heron assembly consisted of a two species of nekton, Mummichog (Fundulus heteroclitus) and Grass Shrimp (Palaemonetes pugio). Among the day herons, dietary compositions overlapped to the extent expected if each individual was foraging randomly. The diet of the Black-crowned Night-Heron diverged significantly from those of the Snowy Egret and Tricolored Heron, but not from that of the Great Egret. Considering relative abundance of different sized Mummichogs, the lengths of dietary Mummichogs overlapped as expected between each heron species. The three day herons coincided in their use of feeding microhabitats, most of which were in the intertidal zone. I found no evidence of social foraging: group sizes of feeding herons were the same as those of herons engaged in other activities, and most birds foraged alone. Foraging birds were rarely aggressive. Similarities (overlaps) in resource exploitation, as measured by type and size of prey and by microhabitat use, were as expected under a null model. Only two of 15 pairwise overlaps were less than expected; two were greater than expected. The four heron species formed an assembly of opportunists, whose members took prey according to abundance. The results provide little evidence that the herons partitioned food resources in any significant way. The lack of competitive or cooperative interactions between herons may be related to the superabundance of a few prey species, a condition probably typical of most estuaries.

We assessed potential factors contributing to variation in counts of staging Bonaparte’s Gulls (Larus philadelphia) on the Niagara River in southern Ontario. Much of the Mississippi Flyway population of this species stages each autumn at this site, en route to the Gulf coast and Mexico. Between 1986-96, weekly or bi-weekly counts were made of gulls flying to their nocturnal roost at the mouth of the Niagara River entering Lake Ontario, to assess the seasonal and temporal patterns of movement. Counts began each year in early October, corresponding to the ‘second wave’ of gulls. Generally, this second wave of autumn movements began in early October to late November (median 1 November) and continued until late January or mid-February (median 5 February). Model selection based on a repeated measures analysis (Generalized Estimating Equations) demonstrated a quadratic relationship between counts and time of year and a linear relationship with daily count duration. Less evidence existed for the role of mean daily temperature in explaining variation (positive relationship) in counts; more data, or inclusion of different weather variables (e.g., wind, cloud cover), may demonstrate that it is more important than our models suggest. Maximum counts were from early November to late January (median 6 December). Peak daily totals per season varied between 6,300 (1993/94) and 40,000 (1990/91). Migration counts may be useful to help monitor populations of this species, provided that variables affecting seasonality in counts are accounted for and the turnover rate of individual gulls staging in the area is determined (e.g., through mark-recapture or radio-telemetry studies).

Great Cormorant (Phalacrocorax carbo) is monomorphic in plumage such that sexes cannot be separated by plumage characteristics. In contrast, it displays sexual size dimorphism, with males generally being larger than females. Sexual dimorphism and variability in size of the continental Great Cormorant (P. c. sinensis) was studied in Greece to develop useful sexing techniques using morphometric measurements. Body mass, wing, culmen, and tarsus length of 81 birds controlled under license were measured during the wintering season in 1999-2002. The sex of each bird was determined by dissection and gonadal inspection. Forward stepwise discriminant analyses were performed to provide reliable functions that would enable the prediction of sex of a bird. Differences in size between adult and juvenile birds were not significant in both sexes, whereas males were larger than females in all measurements. Body mass (19.2%) and culmen length (11.1%) were the most dimorphic variables of those looked at followed by tarsus (6.5%) and wing (6.1%) length. Although wing length was the least dimorphic variable, it also displayed the lowest coefficient of variation (2.3%) thus being the best single measurement for separating the sexes. Three discriminant functions that correctly classified 92.6-95.1% of Great Cormorants of this sample were produced. These functions were reliable (similar accuracy for discriminant analysis and jackknife validation) and seasonally unbiased, as body mass was excluded from the analyses. The function including wing and culmen length as variables showed somewhat lower accuracy when tested with a new sample from The Netherlands suggesting that the obtained functions should be applied with caution to other populations, especially within the area of overlap between the sexes, unless inter-population sources of variation (e.g., geographic variation, hybridization, inter-observer bias) are sufficiently understood.

We used feathers and skeletal measurements, white and black areas at the wing tip and bill morphometrics of Yellow-legged Gulls (Larus michahellis lusitanius) in order to test for possible sex-differences. Overall, 157 individuals from the eastern Bay of Biscay (N Spain) were measured, and the sex determined in 155 individuals, by means of DNA-analyses. All feathers and skeletal-associated measurements, except the distance between each primary (P1 to P5) feather and the wing tip in a folded wing varied between the sexes, with males being larger than females. Sexual selection is discussed to be the major cause explaining these differences. A discriminant function is provided to separate sexes. By contrast, both wing tip patterns of coloration and bill morphology did not vary between sex classes.

Numbers of Black Brant (Branta bernicla nigricans) have declined dramatically in at least one important breeding area in the Western Canadian Arctic (WCA) and the regional population is small and widely scattered. The overall Pacific Flyway Population, to which the WCA Brant belong, has declined historically as well, probably in part due to high rates of harvest and low rates of survival during the 1960s and 1970s. To better understand how changes in survival rates may have influenced WCA Brant, band recoveries and recaptures were used to estimate historical (1962-67 and 1975-79), and more recent (1991-2001) survival rates. On the mainland WCA, adult survival rates (derived from band recoveries) averaged 0.719 ± SE 0.045 and 0.693 ± 0.082 in the 1960s and 1970s, respectively but increased significantly (P < 0.05) to 0.884 ± 0.052 (based on band recoveries of both sexes) or 0.886 ± 0.025 (based on recaptured females) during 1991-2001. Comparable survival rates for juvenile Brant, derived from band recoveries only, were 0.216 ± 0.051, 0.460 ± 0.112, and 0.694 ± 0.205, and increased significantly over time. On Banks Island, located 250 km northeast of our mainland study site, adult survival rates averaged 0.945 ± 0.037 during 1992-94. The harvest of Pacific Flyway Brant has declined substantially since the 1960s which possibly explains much of the observed increase in survival estimates in WCA Brant. The most recent survival estimates for WCA Brant are as high as, or higher than, those for other areas in arctic North America or Eurasia. Managing harvest to maintain current levels of survival, and maintaining or increasing current levels of productivity (known to have declined in at least one important breeding area) may be required to maintain WCA Brant at present population levels.

Inferences on seabird ecology from stable isotopes ratios (δ¹³C, δ¹⁵N) and mercury concentrations analysis of feathers have been made for temperate and polar species but are far more rare for tropical species. In this paper, we used this approach combined with analysis of regurgitations and feeding observations at colonies to examine diet segregation between Roseate Terns (Sterna dougallii) and Lesser Noddies (Anous tenuirostris) breeding sympatrically on Aride Island (Seychelles), western Indian Ocean. Our results indicated extensive overlap between the two species in trophic level and foraging area during the breeding season. Goatfish predominated (93-97%) in all diet samples of adults and chicks collected in the colonies, except in prey fed to mates by Roseate Terns, of which scad and tuna comprised 20%. The isotopic analyses of feathers replaced by adults during molt (primary and body feathers) suggested, however, that the two species differ in foraging ecology during the nonbreeding period. Roseate Tern adults had consistently lower δ¹⁵N values than Lesser Noddies which, in turn, had δ¹⁵N values comparable to those of chick feathers grown on Aride. Moreover, low but similar mercury levels were found in body feathers of Lesser Noddy adults and Roseate Tern chicks, whereas Roseate Tern adults were significantly more contaminated. Overall, these results support the hypothesis that the Lesser Noddy is largely sedentary, being associated with the same food web in the vicinity of the colonies year-round. In contrast, Roseate Terns rely on distinct prey during the molting (nonbreeding) season which may be also consistent with a change in food web (i.e., a migratory regime) although the assignment of potential wintering areas remain difficult without isotopic basemaps currently available for the Indian Ocean.

The Piping Plover (Charadrius melodus) is a federally listed species with three distinct breeding populations, including Great Plains (threatened), Great Lakes (endangered), and Atlantic Coast (threatened), all of which winter along the Atlantic and Gulf coasts of the United States. The spatial distribution and site fidelity of wintering Piping Plovers was investigated on Little St. Simons Island (LSSI), Georgia, from 2003-2006, with emphasis on the conservation significance of this site for the endangered Great Lakes population. Of the individually recognizable color-banded plovers observed on LSSI during 2003-2004 (N = 39), 31% (N = 12) were observed the following year; 69% (N = 9) of plovers that wintered in 2003-2004 returned to winter in 2004-2005. Although good winter survival in 2003-2004 was estimated, survival estimates dramatically declined in 2004-2005. Even with low survival estimates for 2004-2005, 44% of these wintering individuals returned to winter in 2005-2006. Wintering plovers on LSSI were site faithful to particular sections of beaches and occupied small home-ranges. These data on site fidelity and home-range suggest that relatively small areas on LSSI may be of disproportionate importance to wintering Piping Plovers. Critical habitat designations should take account of this within-island variation, and modest detection rates suggest plover numbers could be underestimated by single-visit surveys throughout their winter range.

Approximately 7,610 to 3,175 pairs of Great Blue Herons (Ardea herodias) nested along 420 river km of the Upper Mississippi River (UMR) from 1993 to 2003. Numbers declined precipitously in the mid-1990s stabilizing somewhat in the early 2000s. The average number of nests in colonies was 349 (SD = 283). Annual colony turn over rate for the eleven year period was 0.15 and ranged from 0.06 to 0.29 each year. The number of years that a colony was active was positively correlated with the average number of nests present while the colony was active. Of the eight colonies active in 1993 that averaged more than 349 nests, four were abandoned by 2003. Only one colony grew to greater than 349 nests during the study period. Custer et al. (2004) suggested that herons on the UMR may be limited by forage resources or foraging habitat and social factors, as evidenced by the even spacing of colonies that reflects the maximum feeding range of herons on the river. To rule out nesting and foraging habitat limitation, landscape habitat features of terrestrial and aquatic areas were examined for colony areas and areas without colonies. Available fish monitoring data were used to examine potential interactions between herons and forage resources. Colony areas did not differ from areas without colonies in any habitat feature. Indices of potential heron forage fish increased from 1993 to 2002, although low indices of fish abundance in 1993 were likely influenced by flood conditions that year. Although fish availability to herons is related to flows and water levels, available data suggested that herons did not negatively impact their potential forage base. Numbers of herons were not correlated with indices of fish abundance from the preceding year on a pool-wide scale. Indices of fish abundance were higher within 5 km of colonies than farther than 5 km from colonies, and indices of fish abundance increased from June through August both near and far from colonies. Numbers of herons and locations and sizes of colonies varied annually, whereas landscape features typically vary little if at all from year to year. Indices of fish abundance also varied greatly by sample location and year. Disturbance, particularly by humans in this highly used river, should be examined in relation to limiting foraging opportunities and influencing behavior (colony and individual) and productivity in colonies.

Three statewide surveys in South Carolina for American Oystercatchers, Haematopus palliatus, were conducted during the breeding season from 2001-2003. A mean of 1,105 oystercatchers were recorded each year. In 2002, 407 breeding pairs were documented and in 2003, 397 pairs. There were 378 nonbreeding oystercatchers in 2002 and 383 in 2003. The Cape Romain Region supported a majority of South Carolina’s breeding pairs and nonbreeding flocks. Oystercatchers nested, on average, closer to each other on estuarine islands, (specifically made of shell) and farthest apart on edge shell mounds. Although historically oystercatchers may have nested primarily on front beaches, this study documented only 28% of the breeding pairs on barrier island beaches, 27% on estuarine islands and 45% on edge shell mounds. Twenty-four percent of all pairs in South Carolina were on edge shell mounds adjacent to the Atlantic Intracoastal Waterway (AIWW). Nesting on shell mounds may become increasingly important as beaches become more disturbed by humans and dogs.

Least Terns (Sternula antillarum) have been documented as nesting along the central Platte River of Nebraska since 1949. The very first accounts of birds were on an island “which was formed in the dredging of sand” (Wycoff 1950). Since that time more than 90% of the documented nests occur on human created habitats consisting of commercial gravel mines and constructed river islands. From 1991 to 2005, Least Tern nests were monitored at sandpits that were managed specifically for nesting Least Terns and islands constructed in the Platte River and managed specifically to provide nest sites for Least Terns. In addition a set of sandpits which did not receive any management were monitored from 1994 to1997 to compare reproductive output to the managed sandpits. During the study period 647 Least Tern nests were documented at all sites. Of the nests observed 125 were on unmanaged sandpits, 473 were on managed sandpits and 49 were on islands. Hatching success for those nests was 38% on unmanaged sandpits, 65% on managed sandpits and 71% on constructed riverine islands. A total of 639 Least Tern chicks were observed to have fledged from these nests. Production of fledged chicks per nest for each type of nesting site were unmanaged sandpits 0.56 fledglings/nest, managed sandpits 1.13 chicks/nest and islands 1.04 chicks/nest. Nest success and fledgling survival was significantly greater at managed sandpits than unmanaged sandpits in the 1994 to 1997 time period.

A previously undocumented thermoregulatory behavior of adult cormorants for their pre-fledged young was recorded during observations of a Double-crested Cormorant (Phalacrocorax auritus) colony in Lake of the Woods, Ontario. Many adult cormorants were observed regurgitating water over their chicks’ bodies. The authors believe that the warm temperature, intense sun, and calm winds during the observation periods were the primary factors triggering this previously undocumented thermoregulatory behavior.

A complete tarsometatarsus from a small Pleistocene sinkhole in northwest central Cuba is identified as that of a Bare-throated Tiger-Heron Tigrisoma mexicanum. This constitutes the first record of any kind of tiger-heron (subfamily Tigrisomatinae) in the West Indies. The extinction of the species in Cuba is perhaps attributable to habitat loss due to climatic change.

We report a new locality for the Brazilian Merganser (Mergus octosetaceus), a critically endangered species from Southern and Central South America. The species’ range is considerably extended to the East, and a new habitat and basin used by the species are given. The species was found near the city of Ouro Preto, Minas Gerais State, Brazil, located in a transition zone between the Cerrado and the Atlantic Forest biomes. Our finding improve a little bit the hope for the conservation of the species but more detailed studies to determine if there is a resident population, or if we recorded a vagrant bird, are necessary.

Fidelity of individual shorebirds to stopover sites between years has been documented in only a few species. In May 2005, we recaptured a migrant male Western Sandpiper (Calidris mauri) on the Copper River Delta, Alaska, 5.8 km from its original 2004 capture site. We classified the individual as a first-year bird in 2004 and as an adult in 2005. This report extends our knowledge of site fidelity in migrant shorebirds to one of the most common species on the west coast of North America, and to a small geographic area within a larger stopover site.

Most species of wading birds are monomorphic and present few or no external characteristics to allow for sex determination in the field. We used standard morphometric measurements and discriminant function analysis to determine the sex of Great Egrets (Ardea alba) and White Ibises (Eudocimus albus). The models were validated based on sex determination from DNA. Two functions were created for Great Egrets; mass reliably discriminated 88% of our samples, while wing chord separated 81% of our samples. We included mass in the discriminant function analysis for Great Egrets because mass did not vary between years or within our pre-breeding sampling period. Mass was not included in our analysis of White Ibis because it differed by year and within our pre-breeding sampling period. White Ibis samples were separated by a discriminant function using the length of curved bill and tarsus. This function correctly classified 78% of our samples. We provide simplified linear equations to calculate the sex of Great Egrets and White Ibises as well as cut off points where the probability of correctly sexing individuals drops below 75%. Our model can be used to reduce the costs of sex determination by allowing researchers to use expensive DNA analysis techniques only for those individuals that cannot be reliably classified using the simple statistical model.