The junk-food hypothesis attributes declines in productivity of marine birds and mammals to changes in the species of prey they consume and corresponding differences in nutritional quality of those prey. To test this hypothesis nestling Black-legged Kittiwakes (Rissa tridactyla) and Tufted Puffins (Fratercula cirrhata) were raised in captivity under controlled conditions to determine whether the type and quality of fish consumed by young seabirds constrains their growth and development. Some nestlings were fed rations of Capelin (Mallotus villosus), Herring (Clupea pallasi) or Sand Lance (Ammodytes hexapterus) and their growth was compared with nestlings raised on equal biomass rations of Walleye Pollock (Theragra chalcograma). Nestlings fed rations of herring, sand lance, or capelin experienced higher growth increments than nestlings fed pollock. The energy density of forage fish fed to nestlings had a marked effect on growth increments and could be expected to have an effect on pre- and post-fledging survival of nestlings in the wild. These results provide empirical support for the junk-food hypothesis.

Sexual selection can operate throughout the annual cycle and likely shapes the winter plumage and courtship displays of many northern waterfowl that choose mates during winter. Less conspicuous effects of sexual selection are likely and in this study I asked whether winter distribution patterns and grouping behavior of Harlequin Ducks (Histrionicus histrionicus) are partially shaped by sexual selection. Harlequin Ducks are typically dispersed in small groups and observed grouping behavior supported the hypothesis that unpaired adult and immature birds will show sexually-selected changes in their spacing to facilitate courtship and mate sampling. Unpaired birds occurred in larger groups than paired birds during October-February, and group-related differences in the sex ratio and in the proportion of females that were unpaired indicated that unpaired birds were aggregating specifically for courtship. Behavior similar to lekking was observed at one site. Males gathered at this site at daybreak, unpaired females visited the site each apparently to attract a group of courting males, and these courting groups left the site without feeding. When herring spawn was available in March, unpaired birds were more likely to move to exploit it and gained both direct nutritional benefits as well as indirect benefits related to changes in time budgets and spacing behavior that facilitated courtship and mate sampling. Overall, results suggest that sexually-selected behaviors that affect the process of mate choice and the timing of pairing are important to consider if we are trying to explain winter spacing patterns of waterfowl.

Nesting habitats and nest success of five species of marsh birds were studied during 1997 and 1998 at the Iroquois National Wildlife Refuge (NWR) and the adjacent Oak Orchard and Tonawanda State Wildlife Management Areas (WMA) located in western New York. Nest searches located 18 American Bittern (Botaurus lentiginosus), 117 Least Bittern (Ixobrychus exilis), 189 Pied-billed Grebe (Podilymbus podiceps), 23 Sora (Porzana carolina), and 72 Virginia Rail (Rallus limicola) nests. Average nest densities in 1998, our best nest searching year, ranged from 0.01/ha for Soras (N = 8) to 0.28/ha for Pied-billed Grebes (N = 160). Mayfield nest success estimates for Least Bittern were 80% (N = 16) in 1997 and 46% (N = 37) in 1998. Nest success estimates were 72% (N = 55) for Pied-billed Grebe, 43% (N = 6) for Sora, and 38% (N = 20) for Virginia Rail. Nests of all five species were located in 70% emergent vegetation with a mean water depth of 24-56 cm and an average vegetation height that ranged from 69-133 cm. Logistic regression models were developed for each species using habitat variables at nest and random site locations. Each model was ranked with Akaike’s Information Criterion for small sample size (AIC_c). In general, our best models indicated that increased emergent vegetation and horizontal cover with shallow water depths improved the odds of encountering marsh bird nests in the wetlands of western New York. We suggest that managing wetlands as a complex, at different stages of succession, would best benefit marsh bird species.

From 1997 to 2005, the distribution, seasonal abundance, and age and sex ratios of wintering Barrow’s Goldeneyes (Bucephala islandica) was documented in the St. Lawrence River Estuary and Gulf, Canada, with a combination of ground and helicopter surveys. Ground surveys showed that Baie-Comeau and Baie-des-Rochers were the most important localities, with monthly averages of 250 (max. = 1020) and 273 (604) individuals, respectively, from November through April. Helicopter surveys showed that four areas (Baie-Comeau, Baie-des-Rochers, Baie-Sainte-Catherine and La Malbaie/Cap-à-l’Aigle) harboured on average 74% of all Barrow’s Goldeneyes in the estuary, that numbers of individuals were more stable at these sites, and that the distribution of Common Goldeneyes (Bucephala clangula) within the estuary differed from that of Barrow’s Goldeneyes. Because of ice conditions, goldeneyes were not found on the south shore of the estuary during the coldest winter months, although they were quite numerous in spring and fall. In contrast, large numbers of goldeneyes used the north shore of the estuary all winter long and through the end of April. In January-February of 1999, 2002 and 2005, helicopter surveys (N = 8) yielded on average 2428 Barrow’s Goldeneyes (CV = 8%), 2503 Common Goldeneyes (6%) and 1320 Red-breasted Mergansers (Mergus serrator; 70%) per year in the estuary. These species averaged 2087 (CV = 81%), 2214 (41%) and 2898 (34%) individuals/year, respectively, in the gulf in January-February of 2002 and 2005 (N = 3). Helicopter survey results indicated possible identification errors between these three species, stressing the need to survey them concurrently. The January-February ratio of adult males and ‘brownheads’ was greater in 1998 (57.0%) than in 1999 (51.8%), partly because there were more immatures in the population in 1999 (18.1%) than in 1998 (10.2%). Adult sex ratios were significantly different from 1/1 in January-February of 1998 (P < 0.0001) and 1999 (P = 0.0072), whereas immature sex ratios were not (P ≥ 0.27). The monthly proportion of immatures increased between January and May of 1998 (P < 0.0001) and 1999 (P < 0.0001), because of adults departing for breeding areas. The eastern North American wintering population of Barrow’s Goldeneyes may include a maximum of 6187 individuals, of which >90% would winter along the St. Lawrence Estuary and Gulf. Thus, the St. Lawrence corridor should undoubtedly be considered as the winter stronghold for Barrow’s Goldeneyes in eastern North America

Many bird species use human-made habitats and an important issue is whether these are equally suitable foraging habitats as are historical, natural habitats. Historically, Lesser Snow Geese (Chen caerulescens caerulescens; hereafter Snow Geese) wintered in coastal marshes in Louisiana but began using rice-prairies within the last 60 years. Time spent feeding was used as an indicator of habitat suitability and time and energy budgets of Snow Geese were compared between rice-prairies and coastal marshes in southwest Louisiana. Composite diets of Snow Geese have a lower energy density in the rice-prairies than in coastal marshes; thus, we predicted that Snow Geese would spend relatively more time feeding in rice-praires to obtain existence energy. However, time spent feeding was higher in coastal marshes and thus, not proportional to energy density of composite diets. Snow Geese in coastal marshes ingested less apparent metabolizable energy than did Snow Geese in rice-prairies. In rice-prairies, juveniles spent more time feeding than did adults; however, time spent feeding was similar between age classes in coastal marshes. Undeveloped foraging skills probably cause juvenile Snow Geese to forage less efficiently in coastal marshes than in rice-prairies. These findings are consistent with recent trends in Snow Goose numbers, which increased in rice-prairies but remained stable in coastal marshes.

From May 2000 to November 2003 we studied waterbird use of mangroves, intertidal flats, shrimp ponds and coastal forests surrounding Leizhou Peninsula at the southernmost extent of mainland China. We recorded 61 waterbird species. The most species-rich habitat was intertidal flat with 45 species, followed by mangrove with 38 species, shrimp ponds with 37 species and coastal forest with 15 species. Greatest bird abundance was on intertidal flats, which supported 69% of all birds recorded and 81% of all migrants. Leizhou Peninsula is in the East Asian-Australasian flyway of migratory birds and is an important staging site for migrants. Intertidal flats proved important to nationally and provincially protected and threatened species. Species richness and abundance at shrimp ponds nearly equaled that in mangroves. Charadriids, scolopacids and ardeids used shrimp pond dikes as roosts and foraging habitats during high tides. Shrimp pond dikes play an important role by substituting for natural high-tide roosts such as sandbars, which, in many cases, they replaced. Mangrove-planting programs should avoid conversion of important intertidal flats. When restoring abandoned shrimp ponds, it is also important to retain some dikes as high-tide roosts and foraging areas. Because of the complexity of coastal-zone land administration on Leizhou Peninsula, it is critical that government departments work together to plan and implement mangrove restoration and intertidal flat conservation projects.

One of the proposed benefits of colonial nesting in birds is the protection afforded against avian predators. This advantage may be counter-balanced by the negative effects of intraspecific aggression on breeding success. Effects of nest density, nest location within the colony, and timing of nest initiation on productivity of Caspian Terns (Sterna caspia) were investigated on Crescent Island in the mid-Columbia River, Washington, USA. In the absence of intense nest predation at the Crescent Island tern colony, it was hypothesized that nest density would be negatively associated with productivity. A rangefinder was used to determine spatial distribution of Caspian Tern nests, and these data used to calculate nest characteristics (nest density, nearest neighbor distance, and distance to colony edge) for a randomly-selected subset of nests monitored for nest chronology and productivity. Productivity did not differ between nests in high- and low-density areas of the colony, and was positively associated with earlier nest initiation. Early nests were more productive, were located in areas of higher nest density, and were further from the colony edge than late nests. The strong effect of timing may have been attributable to seasonal declines in prey resources for terns at this site. Our results suggest that Caspian Terns nesting at the highest densities observed in this study did not incur immediate reproductive costs, despite increased potential for encounters between chicks and aggressive conspecific adults.

The breeding population of Double-crested Cormorants (Phalacrocorax auritus) increased in the Beaver Archipelago of northern Lake Michigan, while simultaneously, a Smallmouth Bass (Micropterus dolomieui) population in the region declined. However, the role that cormorants played in this decline has remained uncertain. During summer 2003, VHF radiotelemetry and rafting locations were used to determine whether birds foraged primarily in bass habitat. The foraging activities of ten breeding cormorants were monitored by radiotelemetry from both land and water on a daily basis, weather permitting, throughout the breeding season. In addition, cormorant foraging raft locations were documented by boat survey throughout the breeding season. Radiotelemetry indicated that cormorants typically foraged 2.5 km away from their colonies, at the northeastern end of Beaver Island. This area overlaps with the area determined from rafting locations; however the latter were centered further south. These data allow for better estimation of foraging patch use by archipelago cormorants and indicate that birds are not typically concentrating their foraging in Smallmouth Bass habitat. Cormorants forage in open water in areas with dramatic changes in depth, and these locations agree with diet data that indicates that Alewife (Alosa pseudoharengus) are important prey. Data gathered has led to a better understanding of cormorant foraging patterns in the study area, and indicate that if cormorant foraging areas remain spatially separate from bass habitat, the probability of birds directly impacting these fish is low.

Although chicks of waterbirds usually stay in their nesting territory, in a few species they precociously leave the nesting site and join together in a “crèche”. While several authors have suggested a relationship between crèching behavior and reduced aggression in Larids, quantitative data on aggression in crèching species are missing. In this paper, we quantify the level of aggression through the breeding season in two evolutionarily independent species pairs, each consisting of two closely-related crèching and non-crèching species (Black-billed Gull, L. bulleri, crèching; Red-billed Gull, L. scopulinus, non-crèching; versus Slender-billed Gull, L. genei, crèching; and Black-headed Gull, L. ridibundus, non-crèching). Aggressiveness was similar among species until the chicks were 1-2 weeks old and then decreased in crèching species and increased in non-crèching ones. This change in aggressiveness at an age when chicks usually join a crèche strongly suggests it is related to crèching behavior. To broaden our study we suggest a comparative approach including Tern species.

Sexual size dimorphism (SSD) occurs in the vast majority of birds, although explanations for its existence are controversial. We studied SSD in the Painted Stork (Mycteria leucocephala), a large wading bird, by recording copulating birds on a video camera and obtaining measurements of tibia, tarsus, bill, body length and body depth, on each individual in a pair. Field studies were conducted in the natural heronries of the Delhi Zoo in North India. For quantifying the dimensions of various body parts we improvised upon a microscopic software (MOTIC IMAGES) and developed a protocol for obtaining the dimensions of body parts in metric units. Males were larger than the females in all of the 100 pairs recorded during the study period. A PCA performed on the available data set of male and female independently showed a significant difference in the first PC scores, which were highly correlated with body length in both sexes. A tendency towards positive assortative mating was observed by plotting the male and female values of different variables. There were no significant differences in the median body lengths of individuals recorded copulating early and late in the nesting season. However, early male birds were recorded to have significantly larger tarsus, compared to later birds. The methodology used in this field study has wide applicability for studying the SSD and mating patterns in various groups of waterbirds.

As raptor populations recover following the banning of organochlorine pesticide use, there may be consequences for prey populations. While Bald Eagles (Haliaeetus leucocephalus) actively prey on Glaucous-winged Gulls and their offspring (Larus glaucescens), their presence at colonies and roost sites may also influence reproductive success of gulls by impacting activity budgets. Here we investigate changes in Bald Eagle abundance in relation to gull breeding phenology over 6 years at Seabird Rocks (Vancouver Island, Canada) and compare activity budgets of gulls in relation to Bald Eagle abundance. Bald Eagle abundance varied seasonally, peaking during late incubation and hatching of gull eggs. As Bald Eagle presence increased, gulls showed a strong increase in time allocated to vigilance (54%) and frequency of flushing (up to 6 times/hr). These results indicate that Bald Eagle attendance patterns at gull colonies coincide with hatching of gull chicks and can influence time-activity budgets of gulls. Predator-induced changes in gull behavior during the breeding season may influence reproductive success by impacting time and energy budgets and facilitating egg and chick predation. These findings could be important for understanding failure at gull colonies in Barkley Sound and evaluating impacts of increasing Bald Eagle populations in the region.

Primarily due to loss and disturbance of their open beach habitat, Least Tern (Sterna antillarum) nesting colonies often occur on flat or gently sloped gravel rooftops throughout the Southeastern United States. Currently, these rooftops are being converted to a new substrate, unsuitable for Least Tern nesting, because of changes in state building codes. The purpose of this study was to determine which rooftops Least Terns are currently selecting to help develop man-made structures for nesting and determine where these structures should be placed. From 1998-2003 in Pinellas County, Florida, all previously occupied Least Tern rooftops were surveyed to see if they had a colony and new colonies were located. In 2003, there were 36 rooftops with colonies and 34 unoccupied rooftops that had been previously occupied sometime from 1998-2002 but still had gravel rooftops. In addition, 36 gravel rooftops that had no record of supporting a Least Tern colony were randomly selected. At each building distance to any body of water, distance to a large body of water, distance to a higher building, distance to another colony, height of building, area of rooftop, number of taller trees/poles within 50 m and number of trees that touched the roof were measured. Backwards stepwise regression indicated that only distance to water significantly predicted if a rooftop was currently or never occupied. These results indicate that even relatively small, low structures, located near any body of water may be judged suitable by Least Terns and have the potential to help add to the species’ overall productivity.

Despite recent interest in the interactions between birds and feather microbes, little is known about the identity of these microbes, and all studies of feather microbes thus far have focused on passerines living in temperate regions. Comparisons of the microbial groups living on different groups of birds may provide valuable insight into the ecological roles microbes play on feathers. We used culture-independent molecular techniques to identify the assemblages of bacteria found on the feathers of two closely related seabirds (Crested and Least Auklets (Aethia cristatella and A. pusilla)) and, for comparison, domestic Chickens (Gallus gallus). Some isolates were found on all three species (as well as on other species, as reported in the literature), while others were only found on Auklets. In particular, bacteria of the cold- and salt-tolerant genus Psychrobacter were only recovered from Crested Auklets. These results suggest that some genera of bacteria may be commonly found on birds, while others may be restricted in their distributions.

Forster’s Terns (Sterna forsteri), like most seabirds, are monomorphic and are difficult to sex without extensive behavioral observations or genetic sexing. We conducted the first morphological study and discriminant function analysis on Forster’s Terns to develop a method to accurately identify their sex in the field. A sample of 84 terns from the San Francisco Bay estuary were captured or collected, measured, and the sex of 40 female and 44 male terns was confirmed by genetic analyses or via necropsy. Male Forster’s Terns were larger than females for 7 of 9 morphological measurements, with head-bill length showing the least amount of overlap between the sexes, followed by culmen length and culmen depth at the gonys. Sexual size dimorphism was greatest with retrix R6 length, followed by culmen width, and culmen depth. A discriminant function including only head-bill length accurately sexed 82% of Forster’s Terns, whereas a second discriminant function incorporating both head-bill length and culmen depth at the gonys increased sexing accuracy to 87%. When we used a 75% posterior probability or greater of accurately sexing Forster’s Terns, we excluded only 18% of the sample that overlapped and accurately sexed 94% of the remaining individuals. Our results indicate that Forster’s Terns can be accurately sexed in the field using only 2 morphological measurements.