Cormorants are desirable subjects for food web studies using stable isotopes (C and N) because of global fisheries conflicts, but no validated lipid-normalization procedures are currently available for any cormorant species. Accordingly, the effects of chloroform-methanol and petroleum-ether lipid extractions and three published lipid-normalization models on stable C and N isotope signatures in Double-crested Cormorant (Phalacrocorax auritus) muscle and liver tissues were investigated. The presence of lipids in cormorant muscle and liver decreased δ¹³C values by approximately 1–2‰, more so than has been reported in other birds. Cormorants showed large variation in the relationship between the C:N ratio of bulk tissue and the change in δ¹³C values after lipid extraction, violating a major assumption of published lipid-normalization models. Despite this violation, two of the three tested models performed reasonably well for correcting δ¹³C values. The circumstances under which these models might fail are unknown, so caution is warranted when applying them to new species. Petroleum-ether lipid extractions did not reduce the C:N ratio of tissue samples to those of pure proteins (4.0 or below; over half of the samples ranged from 4.38 to 5.27); thus, lipid extraction using chloroform-methanol is recommended to ensure the greatest accuracy of carbon isotope analyses of cormorant tissues.

Empirical studies testing the predictions of theoretical models on interspecific competition are scarce. The present study focused on the effects of competition on trophic niche by: (1) analyzing temporal changes in the diet of Snowy Egret (Egrella thula) on a Brazilian mangrove swamp before and after its breeding site was colonized by two congeners, Little Blue Heron (E. caerulea) and Tricolored Heron (E. tricolor) ; and (2) comparing spatial changes in the diet of the three egret species at the study site with six additional localities from the literature. Nestling boluses were analyzed in the 1993 and 1994 breeding seasons, when Snowy Egret was the only species in the area, and in 1995 and 1996, when the two other species were present. At the study site, although Snowy Egret consumed a greater proportion of molly fish (Poecilia spp.) than the two other egrets, all egrets fed mainly on mollies and shrimps, providing grounds for competition and trophic interference. However, contrary to the predictions of trade-off models, the Snowy Egret's trophic niche enlarged when the area was colonized by the other two egrets, suggesting that environmental variability is more relevant than competition in shaping trophic niche. The three egrets fed on similar resources to those found at other sites collated from the literature. Tricolored Heron appeared the most specialized species, showing a consistent, mangrove-related diet; Snowy Egret had a similar, but more variable diet, and Little Blue Heron showed the greatest trophic diversity, with a highly variable diet between sites. Overall, temporal and spatial variability in the trophic niches of egrets better match an independently-evolved pattern of resource use rather than predictions from competitive models of niche coevolution.

Near-threatened Black-tailed Godwits Limosa limosa and other shorebirds rely on non-tidal areas during their annual migration but understanding of stopover ecology in these areas is lacking. Here, field observations, analysis of droppings and prey abundance were combined to investigate diet and prey-size selection by Black-tailed Godwits during fall migration in salinas (also called salt works or salt ponds) of southern Europe. Although several potential macroinvertebrate prey species were available and abundant, godwits positively selected the chironomid Chironomus salinarius. The larvae and pupae of this prey represented >95 % of the total number of items present in droppings during migration (July-September). Consumption of prey of a given size class was not dependent on its abundance. Thus, although larger size-classes of chironomid larvae were not necessarily the most abundant for some months (mean size of available larvae: 8.2 ± 0.2 mm, 6.4 ± 0.2 mm and 8.4 ± 0.2 mm in July, August and September, respectively), they were the ones most frequently consumed by the godwit (mean size of larvae predated: 9.9 ± 0.8 mm, 9.2 ± 1.7 mm, and 9.4 ± 1.3 mm in July, August and September, respectively). The role salinas play as stopover foraging areas for godwits appears dependant not only on the abundance of C. salinarius but also on the abundance of large size-classes of this soft-bodied prey. Conservation and management of salinas that allows the production of high densities of chironomids during the peak of Black-tailed Godwit migration would assist the conservation of this species.

Western Sandpipers and Dunlin are capable of grazing biofilm. As there has been no assessment of this dietary constituent in stomach contents, the stomachs of 89 Western Sandpipers and 56 Dunlin collected during breeding migration through the Fraser River delta, British Columbia, Canada, were examined. Invertebrates, traditionally regarded as the principal prey, comprised a minor fraction of mean stomach volumes (Dunlin: <25%; Western Sandpiper <10%). Three phyla accounted for most of these invertebrates: molluscs, annelids and arthropods. In comparison, sediment (a mixture of sediment particles, broken and unbroken diatoms plus organic detritus) comprised the major component of stomach volumes (Dunlin: >40%; Western Sandpipers: >75%). Although the mean volume of sediment was significantly greater in Western Sandpipers than Dunlin, there was no effect of sex for either species. Stomach sediment volume appears a convenient index of biofilm intake and sediment loads indicative of biofilm grazing have been reported in stomach contents from other shorebird species. Re-examination of shorebird diets appears necessary given that conditions promoting biofilm are not necessarily conducive for invertebrate prey.

Existing hypotheses only partially explain male biased parasitism in mammals and birds. The present study examined whether male biased parasitism by a common trematode and nematode exists in breeding Doublecrested Cormorants (Phalacrocorax auritus) from Lake Erie and if any sex bias in parasitism could be explained by sex differences in body size and foraging ecology, evaluated using stable isotope profiles (based on δ¹³C, δ¹⁵N). Male cormorants had three times the abundance of Drepanocephalus spathans (a trematode) than females; however, there were no significant sex differences in abundance or intensity of Contracaecum spp. Relationships between body size and parasitism were either non-existent or inconsistent. Stable carbon isotope profiles indicated that male and female cormorants that foraged in more pelagic habitats had more Contracaecum spp. In summary, male biased parasitism was present in a sample of Lake Erie cormorants and differences in foraging ecology might affect the levels of parasitism in cormorants.

To face energetic demands of reproduction, female birds need to build up body reserves before breeding and/or feed while producing eggs and incubating. Five female Common Eiders were implanted with data loggers that recorded flying and diving activity for a year. The pre-laying period, defined as the interval between the end of spring migration and laying of the first egg, extended over eleven to 27 days and represented a period of intense foraging activity. Daily time spent diving (DTSD) during the pre-laying period averaged 159.6 ± 16.0 min compared to an annual average of 91.4 ± 37.8 min. Diving decreased to 69.8 ± 7.4 min during laying and became almost negligible at the onset of incubation. Females showed hyperphagic behavior during follicular growth, suggesting that they may directly utilize ingested food for egg production and laying. Given the small number of instrumented females, available evidence was reviewed on foraging and time of arrival in various populations and subspecies. Despite large variations in migration distance, the pre-laying period was similar to other populations (16–28 days), as well as DTSD (160–211 min). Reduced take-off capability may constrain the timing of accumulation of body reserves and foraging effort. Further, the level of body mass required for nesting (laying and incubation) was estimated to be 543 g higher than in winter, of which about 41–72% would be accumulated on the breeding grounds. Protection of foraging areas during the pre-breeding period is important to maintain healthy populations.

Rice fields in southwestern Louisiana provide breeding habitat for several waterbird species; however, little is known about nest density, nest survival and the importance of landscape context of rice fields in determining breeding activity. In 2004, 42 rice fields were searched for nests, and 40 were searched in 2005. Land uses surrounding rice fields, including irrigation canals, trees, crawfish ponds, rice, fallow and soybean fields, were examined to determine influence on nest density and survival. Nest densities were 13.5–16.0 nests/km² for Purple Gallinules (Porphyrio maitinica), 3.0–13.7 nests/km² for Fulvous Whistling Ducks (Dendrocygna bicoloi), 2.6–2.8 nests/km² for Common Moorhens (Gallinula chloropus), 0.3–0.92 nests/km² for Least Bitterns (Ixobiychus exilisi) and 0–0.6 nests/km² for Mottled Ducks (Anas fulvigula). Nest survival was 52–79% for Purple Gallinules and 39–43% for Fulvous Whistling Ducks. Apparent nest success of Common Moorhens was 73–75%, 83% for Least Bitterns and 33% for Mottled Ducks. Purple Gallinule and Common Moorhen nest densities were highest in fields with a larger proportion of irrigation canals surrounding rice fields. Purple Gallinule nest densities were greater in fields devoid of trees and landscapes dominated by rice fields and pasture, rather than landscapes containing soybean fields and residential areas. Fulvous Whistling Duck nest densities were higher in agriculturally-dominated landscapes with few trees.

Movements of adult Snowy Plovers (Charadrius alexandrinus nivosus) tending broods were examined in coastal northern California. Chicks moved an average of 518 ± 52 m from their nests one to three days after hatch; thereafter, movements decreased. In their first ten days, there was no difference in distances moved or home range size between chicks that eventually fledged and those that died. Plovers consistently used the same areas of the beach each year, and these areas were positively associated with nest locations and negatively correlated with human activity. A fenced refuge for breeding plovers was created in the area most used by humans. Fledging success doubled in the refuge during the five years it was protected (37% chicks survived), compared to three years when the area lacked protection (15% chicks survived).

Trumpeter Swan nesting in Yellowstone was monitored from 1987–2007 to assess the effects of environmental conditions, density-dependent factors and habitat characteristics on two metrics of productivity: clutch size and fledging success. Average clutch size was 4.2 eggs per nest (range = 3–6, SE = 0.2) and a positive relationship was found between clutch size and area of wetland complex surrounding the nesting site. The probability of fledging success (survival until September of at least one cygnet per nest) was associated with an increasing metric of territory quality (measured as historical site use from 1931–1986) and decreasing April precipitation. The probability of fledging success was estimated to range from 0.062 (95% CI = 0.060, 0.064) for a nest located in a wetland occupied only one time historically to 0.275 (95% CI = 0.073, 0.466) in a wetland occupied 38 times historically. The need to protect and maintain high quality nesting areas is underscored by the variability among nesting territories. The importance of adult survival is highlighted by the low productivity of Yellowstone Trumpeter Swans because pairs likely need to survive and nest many times to replace themselves.

Mallard (Anas platyrhynchos) populations in the Lower Mississippi Alluvial Valley (hereafter, LMAV) comprise the largest concentration of wintering Mallards in North America. Radiotelemetry techniques were employed to assess movements by female Mallards during winters of 2004–2005 and 2005–2006; 467 paired (diurnal and nocturnal) observations on 80 radiomarked females were attained to assess effects of date, female age, hunting regime and habitat type on distances moved and potential habitat switching. Distance moved increased with date for females diurnally located in RICE but decreased for females in FOREST. Median movement distance was 1.5 km, suggesting suitable habitats for all activities were in close proximity. Habitat switching varied among diurnal habitat types used by females. Females diurnally located in FOREST and REFOR switched habitats in ≤22% of paired observations, whereas females diurnally located in RICE switched habitats in 55% of paired observations. The decreased movement distances and less frequent habitat switching by females using forested habitats should reduce their energy expenditure and exposure to predation risk. The results document the importance of forested wetlands to Mallards wintering in the LMAV and provide support for programs that protect and restore such habitats.

Southward migrating Red Knots (Calidris canutus) were surveyed on Cape Cod, Massachusetts. Unique markers, including ones applied to birds in wintering areas in North and South America, were found. Northern and southern-marked knots had different migration chronologies, plumage characteristics and flight feather molt. Knots from the two groups were found to have different foods and foraging habitats. Numbers of knots more than one year old were found to increase from mid-July to mid-August, decline during late August and then increase in September–October. As numbers declined in August, the proportion of knots from South America decreased and, by 1 September, all remaining marked birds had been tagged in North America. Average minimum stopover durations were found to vary according to original banding locations, e.g. 8.5 (±2.6) days for South America, 14.2 (±3.2) days for Delaware Bay, 16.1 (±3.5) days for the U.S. mid-Atlantic coast and 49.5 (±24.6) days for Florida. The proportion of knots with alternate plumage was higher in July–August than in September and by mid-October almost all had basic plumage. Also, low numbers (tens) of basic-plumaged knots—probably one-year-old subadults were found during July–August; most had active flight feather molt. First-arriving juvenile knots were seen beginning in the third week of August and their numbers peaked in mid-September. Differential uses of foraging and roosting habitats were found to be related to migration destinations. Vital habitats that should be managed for protection of threatened Red Knots at this key southward migration stopover area were identified.

The Least Bittern (Ixobrychus exilis) and the Pied-billed Grebe (Podilymbus podiceps) are secretive marsh bird species that breed in the Illinois and Upper Mississippi River Valleys. Marsh bird surveys were conducted on public and private wetlands in this region during the breeding seasons of 2006 and 2007. Detection probability () and site occupancy probability () were estimated for each species separately for each year. Candidate models including sampling and habitat covariates were compared using AIC_c to determine what variables had the greatest influence on and . Average for Least Bitterns was 0.29 in 2006 and 0.18 in 2007, and varied throughout the 2007 survey season. Average for Pied-billed Grebes was 0.44 in 2006 and 0.22 in 2007, and an observer effect was found in 2007. Overall for Least Bitterns was 0.17 in 2006 and 0.14 in 2007. Least Bittern occupancy was positively related to tall emergent vegetation cover in both years and to water-vegetation interspersion in 2007, and was negatively related to woody vegetation cover in 2007. Overall for Pied-billed Grebes was 0.21 in 2006 and 0.31 in 2007. Pied-billed Grebe occupancy was negatively related to woody vegetation cover in both years, and was positively related to areas of open water in 2006. Land managers targeting these species should provide wetlands free from woody vegetation with extensive areas of open water for Pied-billed Grebes, and tall emergent vegetation interspersed with small pools of water for Least Bitterns.

A reliable and effective technique for capturing rails would improve researchers' ability to study these secretive marsh birds. The time effectiveness and capture success of four methods for capturing rails in emergent marsh and agricultural wetlands in southern Louisiana and Texas were evaluated during winter and breeding seasons. Methods were hand and net capture from an airboat at night, an all-terrain vehicle (ATV) at night, an ATV during daylight rice harvest and passive capture using drop-door traps with drift fencing. Five hundred and twenty rails were captured (and 21 recaptures): 192 King Rails (Rallus elegans), 74 Clapper Rails (R. longirostris), 110 Virginia Rails (R. limicola), 125 Sora (Porzana Carolina) and 40 Yellow Rails (Coturnicops noveboracensis). Methods used at night were effective at capturing rails: capture from airboats yielded 2.13 rails per hour each airboat was operated and capture from ATVs yielded 1.80 rails per hour each ATV was operated. During daylight, captures from ATVs during rice harvest (0.25 rails per hour each ATV was operated) and passive drop-door traps with drift fencing (0.0054 rails per trap hour) were both inefficient.

Open marsh water management (OMWM), a method of mosquito reduction through habitat alteration, is widely practiced in Mid-Atlantic salt marshes. The effect of these habitat modifications on obligate salt marsh breeding birds is poorly understood. The present study was conducted to quantify the extent of OMWM and determine if the technique affected Seaside Sparrow (Ammodramus maritimus) reproductive success and nesting ecology. Seaside Sparrow territory density, nest density, nest survival, productivity and vegetation cover was estimated on 19 plots (1–3 ha) within tidal marshes in Sussex County, Delaware in May–August 2006–2007. Plots were characterized as limited (N = 10) or extensive OMWM (N = 9) based on the amount of alterations and time since manipulations. Seaside Sparrow territory density and nest density were two times greater on limited OMWM plots than extensive OMWM plots. Also, the number of Seaside Sparrow eggs/ha and fledglings/ha were greater on limited OMWM plots. Seaside Sparrow nest survival rates did not differ between limited and extensive OMWM plots, but reproductive output (# nests/ha, eggs/ha, and fledglings/ha) was greater on areas with limited OMWM. OMWM may be an alternative means of mosquito control but should not be considered a method of habitat enhancement for Seaside Sparrows and possibly other obligate salt marsh bird species.

Loss and modification of tidal marsh habitat has contributed to the decline of marsh bird species. For many marsh birds that inhabit tidal ecosystems, little information exists on habitat use, particularly in relation to movement and response to prey availability. In this study, radio-telemetry was used to investigate home range size, movement patterns and response of Clapper Rails (Rallus longirostris) to prey availability within tidal marshes in coastal Mississippi. Mean fixed kernel 95% home range for breeding Clapper Rails was 1.37 ha ± SE 0.27 (N = 10 birds) with a 50% core use area 0.32 ha ± SE 0.07 (N = 10 birds), which are estimates similar to those obtained throughout this species' range. The extent of Clapper Rail movements during the incubation period was negatively correlated with density of fiddler crab burrows within 50 m of nest sites. Clapper Rails' use of marsh edge decreased relative to tidal height. Use of this habitat type may have been further restricted during the first few weeks of the parental-care period when adults were caring for recently fledged young. Collectively these results illustrate the importance of edge and interior marsh habitats and may provide an explanation for the variation in Clapper Rail densities found within and between tidal marsh systems.

Monitoring programs aimed at understanding the population trends of secretive marshbirds can be altered to benefit from the creative interplay between predictions, designs and models, and provide the template for doing so. Effective application of information to decision making typically requires integration of several types of information in a common framework, including “found” data and retrospective studies, innovative sampling designs and the use of hierarchical data structures. Hierarchical and state-space modeling provide a unified modeling structure for such designs and data. These ideas are illustrated with the problem of investigating and mitigating the effects of climate change on secretive marshbirds in coastal North America. How both ecological theory and available data can be used to provide predictions about the impacts of regional and local climate changes on these avian communities are illustrated.

A small, isolated population of Common Terns (10–30 pairs) has bred at Bermuda since at least the 1920s. In September 2003, a hurricane eliminated all the adult males; only females returned in 2004 and these paired together and laid clutches of three–seven infertile eggs. The breeding population was re-established in 2005–06 by four adult males that had been too young to breed in 2003–04. These males paired with females that were probably young and bred with high success (mean 2.6 fledged chicks/pair) through 2009. Two males apparently each mated with two females to form productive trios. The old females continued to pair together and lay infertile eggs, even though males were raising chicks on the same islets. Consequently, the effective population size at the ‘bottleneck’ was only four males and four females. Although the population is now increasing rapidly, it remains critically endangered.

The Dovekie (Alle alle) is a small colonial High Arctic-breeding seabird that lays a single egg clutch. Occasionally, two eggs have been observed in Dovekie nests although incubation of both eggs has not previously been documented. Here, the incubation of a two-egg clutch by both members of a pair over an extended period is described and the origin of the eggs plus value of the observation discussed.

A feather-loss disorder, first observed in captive African Penguin (Spheniscus demersus) chicks in a South African rehabilitation center in 2006, was found one year later in wild Magellanic Penguin (Spheniscus magellanicus) chicks in four colonies in Argentina. Two years later, it was found in African Penguin chicks in the wild. The featherless African Penguin chicks in the rehabilitation center (N = 176) lost their down and emerging juvenile feathers, remaining featherless for several weeks until they died (N = 31) or grew juvenile (N = 3) or adult plumage (N = 145) before being released. The featherless African Penguin chicks took 16 days longer to reach the rehabilitation center's standards for release than feathered chicks (t₁₇₆ = -8.8, P < 0.00001). Likewise, the featherless wild Magellanic Penguin chicks (N = 13) lost their second coat of down, remaining featherless for several weeks; but those that survived to fledging all grew normal juvenile plumage (N = 4). Featherless Magellanic Penguin chicks grew more slowly and were smaller at fledgling age than most feathered chicks. The disorder in Africa and Argentina is new, rare, and more common in a rehabilitation center in Africa than in the wild. The cause of the feather loss is unknown, but the disorder results in slower growth, smaller fledglings, and appears to increase mortality in Magellanic Penguin chicks in the wild.