Nesting distribution, abundance, and reproductive success of colonially nesting herons and egrets in the central coastal region of California surrounding the San Francisco Estuary were analyzed from 1991 to 2005. Nesting activity among nine major wetland subregions was compared with regard to nesting distribution, nest survivorship, productivity of successful nests, habitat characteristics, and intraseasonal timing. An average of 73 active colony sites y-1 supported approximately 62 Great Blue Heron (Ardea herodias) colonies, 25 Great Egret (Ardea alba) colonies, 13 Black-crowned Night-Heron (Nycticorax nycticorax) colonies and twelve Snowy Egret (Egretta thula) colonies each year. Regional nest abundances were stable or increasing in all species. Annual changes in nest abundance were consistent with shifts in colony site preference as wetland suitability and disturbance patterns fluctuate across years and over space. Decreases in colony size were significantly related to higher rates of nest mortality, suggesting that conspecific nest failure may stimulate shifts in breeding distribution. A sharp decline in regional nest abundances suggested the effects of reduced recruitment associated with increased juvenile mortality in winter, rather than a decline in productivity. Persistence of colony site use increased substantially at sites that reached at least 20 active nests. Subregional increases in nesting abundance coincided with the restoration of tidal marshes. Significant declines in regional reproductive success of Great Blue Herons, Black-crowned Night-Herons, and Snowy Egrets resulted primarily from declining nest survivorship, which coincided with regional increases in abundances of Common Ravens (Corvus corax). We found small but significant subregional differences in nest survivorship, productivity, and overall reproductive success. Local and subregional productivity of successful Great Blue Heron and Great Egret nests fluctuated within larger-scale variation across the region, whereas nest survivorship was associated with processes at local or subregional scales.

Numbers of California Brown Pelicans (Pelecanus occidentalis californicus) along the coast of Oregon and Washington have increased sharply in recent years. We identified East Sand Island in the Columbia River estuary as the site of the largest pelican roost within this region. Numbers of pelicans roosting on East Sand Island have increased from less than 100 during 1979-1986 to a high count of 10,852 in 2002. The East Sand Island roost is currently the site of a major non-breeding aggregation of this endangered subspecies. Total numbers of pelicans roosting on East Sand Island increased seasonally from April to September or October, and then declined sharply with the onset of winter storms. Pelicans appeared to forage more during low tides, and return to the roost during high tides; therefore, pelican numbers on the island were positively associated with tide height. Land-based human disturbance was negatively associated with total pelican numbers, whereas water-based human disturbance had no significant effect on total pelican numbers on the island. Natural disturbances, although more frequent than human disturbances, apparently did not influence the total number of pelicans on the island.

The current male-costs hypothesis to explain variation in the timing of pairing in waterfowl acknowledges that relative parental investment and intra-sexual competition among males place females in control of pairing in most species. However, because females may benefit from early pair formation, it assumes that they should be willing to pair whenever males are energetically capable, and thus predicts that timing of pairing depends on decisions made by males. A compilation and review of available data on pairing behavior in waterfowl found little support for this hypothesis and considerable data that were inconsistent with its predictions. The mutual-choice hypothesis extends the male-costs hypothesis by incorporating cost-benefit trade-offs to females as well as males, and by giving more consideration to the various components of the pairing process, including time and energy invested into mate choice, the quality of mate chosen, and the state of being paired, including possible benefits of time spent gaining familiarity with a partner before breeding. This hypothesis differs from the male-costs hypothesis in two essential points: 1) that decisions by females rather than males primarily determine the timing of pairing, and 2) that it is necessary to incorporate the process of choosing a partner as well as the state of being paired. The new hypothesis was supported by available data and by results of preliminary, comparative analyses, and provides a theoretical structure to describe phylogenetic trends in pairing behavior. However, critical testing of many predictions is currently hampered by a lack of longitudinal data on age- and sex-specific pairing chronologies using individual-based measures of pairing chronology.

Intra-specific predictions of the male-costs and mutual-choice hypotheses to explain variation in the timing of pairing in waterfowl were tested in a longitudinal study of marked, known-aged Harlequin Ducks (Histrionicus histrionicus). Pairing chronologies and seasonal changes in time-activity budgets and rates of aggressive interactions were compared in relation to sex, age, and paired status. Results supported the mutual-choice and not the male-costs hypothesis. Paired females gained no immediate benefits relative to unpaired females from mate defense and vigilance, and there was no evidence that females preferred to pair as early as possible, as postulated by the male-costs hypothesis. Unpaired males spent much more time in courtship than paired males spent in mate defense and constraints on male time and energy budgets was not a plausible reason for delayed and protracted pairing of young and re-pairing females. As predicted by the mutual-choice hypothesis, decisions by females about how much time and energy to allocate to the pairing process appeared to be the main factor controlling the timing of pairing in Harlequin Ducks. Newly-pairing females invested an extended period of time in courtship and mate sampling before pairing, in spite of an abundance of courting males clearly energetically capable of maintaining a pair bond. Many young females decided to pair during mid-winter when time constraints to males should have been most severe. Time-budget trade-offs were apparent for young females and their date of pairing was related to the amount of time per day that they allocated to courtship. Pairing success of males was not related to their rate of courtship, nor was it related to the length of time they invested in courtship as they began courting while they were still immature and generally courted for several years before pairing.

We describe and analyze the bird community composition of the lacustrine water bodies of the seasonally flooded wetlands of the Mamirauá and Amanã Reserves, Amazonas, Brazil. Bird surveys were conducted in 54 water bodies within four water body systems aboard a speedboat, in July 2003, at the peak of the high water season. We recorded 2,823 individuals representing 79 bird species associated with aquatic environments, mostly resident; of these, 34 were aquatic (exclusively associated with aquatic environments), and 19 were primarily piscivorous. The aquatic bird communities of Mamirauá and Amanã comprise a few abundant species and a higher number of rare species. Seven species accounted for 71.7% of all 34 aquatic birds recorded. In general, the more elongated the water bodies, the lower the aquatic and piscivorous bird species richness, and the lower the bird abundance. Piscivorous bird abundance was not significantly related to water body shape. Matrices of bird species by water body were subjected to multivariate analysis using Principal Co-ordinate Analysis (PCoA). For the quantitative data (species abundance) and qualitative data (species presence/absence), the composition of the community of aquatic birds changed significantly among lacustrine water body systems, and was significantly affected by water body shape. The quantitative and qualitative composition of the piscivorous bird community did not change significantly among water body systems, and were not affected by water body shape. The numerical analyses revealed a remarkably different behavior of the communities of aquatic birds and piscivorous birds, the former changing significantly with lacustrine water body morphology and local geography (water body system), and the latter being relatively insensitive to variation in these parameters. Water body shape is one of the determinants of aquatic bird community composition in the seasonally flooded wetlands of this part of Amazonia.

The rainfall regime of the Pampas region of Argentina shows a long-term cyclic behavior that has increased in intensity over the historical mean during the last four decades. In this paper we explored the effects of changes in monthly cumulative rainfall on lagoon and riparian habitat, and, in turn on the wetland waterbird community. We also explored the responses of waterbird morphofunctional groups to fluctuation in water level and habitat diversity caused by the change in rainfall at the Mar Chiquita Coastal Lagoon, Argentina (37°32’ to 37°45’S, 57°19’ to 57°26’W). Analysis of satellite images shows that increases in rainfall increased wetland water surface, but reduced riparian habitat area and habitat diversity. Increases in water surface negatively affected the abundances and species richness of waterbirds; habitat diversity did not explain a significant portion of total waterbird variability. Shorebirds (i.e., yellowlegs, plover, sandpiper) were the most affected by reduction in mudflats and habitat diversity. Other waterbirds (i.e., long-legged wading birds, waterfowls) were affected by increases in water surface (ducks, swans, long-legged waterbirds and gulls), decrease in mudflat availability (long-legged waterbirds and gulls), and decrease in habitat diversity (ducks). Our results show that the inter-annual variability in the rainfall pattern influenced the presence and abundance of most waterbirds, and species richness and composition. Fluctuation in water depth per se is known to be a key factor for habitat use of many waterbirds, but habitat diversity also needs to be considered.

We assessed the effects of the presence and the frequency of canoe and pedestrian disturbance during two breeding seasons on multiple behavioral responses (scanning, freezing, grooming, sleeping, moving, wing-raising, and standing-up) of Black-crowned Night Heron (Nycticorax nycticorax) nestlings in a breeding colony in southeast Chicago. Short-term responses (min) of Black-crowned Night Heron nestlings showed that they were sensitive to the presence of aquatic and pedestrian disturbance by increasing vigilant (scanning) and anti-predator (freezing) behaviors and decreasing maintenance (grooming, sleeping) behaviors. Nestlings were also sensitive to recreationist behavior, with less time allocated to sleeping and more time to freezing and scanning in the presence of inquisitive pedestrians than pedestrians who passed by the colony without stopping. However, medium-term responses (days) were insensitive to the frequency of disturbance, but spatial proximity to the source of disturbance influenced time scanning, sleeping, and freezing). Our results have wide implications for the protection of the Black-crowned Night Heron in States in which it is considered a species of conservation concern. We recommend that boating activities should be precluded during the initial part of the breeding season and buffer zones of 50 m should be established around the colony to minimize human disturbance. However, under these conditions, restrictions on the number of visitors during the breeding period may not be necessary.

Each spring, Black Scoters (Melanitta nigra), Surf Scoters (M. perspicillata) and White-winged Scoters (M. fusca), pass through the Bay of Fundy in daytime on their northward migration to the sub-arctic breeding grounds. Their migrations along the Fundy coast were monitored from the Point Lepreau Bird Observatory at Point Lepreau, New Brunswick, from 1996 to 2004. Black Scoters migrated first (peak migration day: 13-17 April), followed by Surfs (23-25 April) and White-wings (22-28 April) which migrated together, although White-wings persisted over a longer period. Based on their rates of passage, we estimated the relative proportions of the wintering eastern North American populations of scoters, assumed to be of breeding age, which migrated by Point Lepreau each spring. We determined that 6-18% and 28-37% of the North American breeding populations of Surf Scoters and Black Scoters, respectively, utilized this northward migration route annually. The low numbers of White-wings (0.4-0.6%) suggested that larger numbers of this species employed a different migration route in spring or migrated at night. This observatory offers an exceptional facility for monitoring this group of sea ducks, over time.

Red, orange, and yellow carotenoid-based coloration abounds in birds, with over half of all avian orders known to display it in some form. Penguins (Order Sphenisciformes), however, are one order of birds for which the proximal causation of ornaments is unclear, i.e., whether such colors in plumage or bare-parts are carotenoid-based. We experimentally supplemented the diet of captive Gentoo Penguins Pygoscelis papua for two months with extracts of krill, a common carotenoid-rich food source for these animals in the wild, to determine whether orange coloration in the beak and feet is influenced by carotenoid content of the diet. We found using UV-Vis reflectance spectrophotometry that dietary carotenoid enrichment elevated beak but not foot brightness. This suggests that the crustacean part of the diet is at least in part responsible for orange beak coloration but not feet in Gentoo Penguins and that, like other carotenoid signals, these traits have the potential to reveal important aspects of mate quality (e.g., nutrition, health).

We identified foraging locations during a two-year radio telemetry study (2003-2004) and described chick diets over a seven year period (1999-2005) for co-nesting Arctic (Sterna paradisaea) and Common Terns (Sterna hirundo) at Country Island, Nova Scotia, Canada. The results of the radio telemetry study showed that both species foraged within nine km of the breeding colony, however, Arctic Terns foraged in deeper water on the seaward side of the colony while Common Terns foraged in relatively shallow water between the colony and the mainland. The results of the diet study showed that chick diets overlapped significantly, with both species feeding mostly on hake (Urophycis sp.) and sand lance (Ammodytes sp.). Despite the overlap in diet, Arctic Terns delivered proportionally more hake and less sand lance than Common Terns and the sand lance they delivered were smaller on average than those delivered by Common Terns. Overall, Arctic and Common terns at this site show foraging habitat segregation, but similar chick diets.

Until recently, our understanding of the role of movement in animal populations was limited due to a prevalence of studies on single local populations. Here we report on local and regional movement patterns of Razorbill (Alca torda), the least numerous Atlantic alcid, through the use of multi-site capture-mark-recapture/resight for five breeding locations spanning their entire North American breeding range. Razorbill philopatry and breeding site fidelity rates for the Gannet Islands, Labrador were high with 83% of young birds (N = 340) and 97% of adults (N = 149) returning to the same colony to breed. The distance moved between the natal colony and the colony where an individual later bred was significantly greater for birds banded as chicks, both between colonies on the same island and within islands in the Gannet Islands cluster. Regional movements of 40 banded individuals were recorded during 2003-2006, including seven birds that were confirmed breeding at a location different from their natal colony. Emigration distances among colonies in North America ranged from 57 to 1,737 km, providing an unexpectedly high rate of movement of birds between breeding colonies that has not been previously reported for any auk species. One bird, banded as a chick on Digges Island, Nunavut in 1982 was recaptured 24 years later as a breeder on the Gannet Islands (1,737 km away). A chick banded on Handa Island, Scotland in 1971 was seen four times in 2004 at the Gannet Islands (3,210 km away). Despite exhibiting low productivity and survivorship, Razorbill populations at some Atlantic Canada breeding sites have been increasing. We conclude that the dispersal and recruitment of individuals into new colonies that are characteristic of other seabird species may also partly explain patterns of population dynamics at North American Razorbill colonies.

Understanding how Interior Least Tern (Sternula antillarum athalassos) chicks hatched on rooftops interact with their environment is essential in the conservation of roof nesting colonies. We observed a colony of terns nesting on gravel roofs in Denton County, Texas, in 2003 and 2004. We used focal sampling to examine how chicks behave in relation to surface temperatures and in the presence of predators. We also placed two types of structures, artificial plants and wooden teepees, on the roofs to determine whether chicks would use them for shade or for protection from predators. As surface temperature increased, chicks increased time spent under cover (whether a man-made structure or being brooded) and decreased intraspecific interactions (ducking while an adult flew over, attacking or being attacked by other terns, submissive behaviors, and posturing). As chicks matured shade use decreased and body maintenance (preening and scratching) increased. When adults were mobbing potential predators over the colony, chicks ceased body maintenance, flight muscle preparation (stretching wings or flapping wings), and intraspecific interaction. Most chicks either fell prostrate where they stood when mobbing began or ran away from the predator. The use of structures by chicks did not change in the presence or absence of potential predators. Of the two experimental structures, only artificial plants were used more than expected. Overall, chicks hatched on roofs survive high surface temperatures by relocating to shade and survive predation by running or using camouflage. Artificial plants may be important for providing shade but not for providing protection against predators.

The Common Gull (Larus canus) is a typical breeding bird species of the Baltic Sea coast in Schleswig-Holstein, northern Germany, where it has declined substantially in recent decades. Since the mid-1990s, Common Gulls have started to colonize flat roofs of buildings, consisting mostly of gravel and small stones. The total number of roof-breeding Common Gulls in Schleswig-Holstein is estimated to be at least 400-450 pairs for the period 2000-2005, with further increasing trends. Minimum reproductive performance at two colonies in 2000 was 0.9 and 1.8 fledged chicks per nest. The diet at two colonies studied in July 2001 consisted mainly of terrestrial food items. The most important prey categories were cherries, lumbricids, insects and bivalves. It is concluded that Common Gulls show a flexible response to environmental conditions by successfully exploiting a new breeding habitat, by reproducing successfully there and by taking benefit of their wide food spectrum to exploit man-made sites.

The New World Snowy Egret (Egretta thula) and Old World Little Egret (Egretta garzetta) are ecologically similar and historically allopatric species both of which recently colonized Barbados, West Indies, as breeding species. Examination of their foraging behavior in their zone of recent sympatry suggests that they choose the same (very limited) foraging sites but differ in foraging behavior. The larger Little Egret was more active and diverse in its foraging, fed more in upright posture, chose open, unvegetated sites more frequently, and was dominant over the Snowy Egret. The conservation situation in Barbados for these two species, and their thus-far unique sympatry, is uncertain as both feeding and nesting sites are far from secure.

Seabirds and other colonial waterbirds nesting in the northern Bahamas are nearly undocumented. This study is the first complete inventory of seabirds and other colonial waterbirds nesting in the northern Bahamas (including the islands of the Abacos, Grand Bahamas, Biminis, and Berries). The survey found 20,267 nests of 19 species of seabirds and other colonial waterbirds at 113 colony sites. The over 40,000 seabirds and other colonial waterbirds found nesting in the northern Bahamas doubles population estimates previously published for The Bahamas as a whole, which included few of these sites. Sooty Tern (Sterna fuscata) was the most abundant species, having a nesting population of over 10,000 pairs. Next most abundant were the Bridled Tern (Sterna anaethetus), Laughing Gull (Larus atricilla), and Brown Noddy (Sterna stolidus). This paper documents the first nesting record in the Commonwealth of The Bahamas of the White Ibis (Eudocimus albus), the first recent nesting in northern Bahamas of the Magnificent Frigatebird (Fregatta magnificens), and the first recent nesting in Grand Bahama of the Brown Pelican (Pelecanus occidentalis). Based on the results, 27 sites may be recognized as of special importance to seabird conservation in the northern Bahamas. Opportunities for conservation, including community-based colony site stewardship and protection of the most important sites within twelve protected areas are discussed.

Super-normal clutches (five eggs or more) in the Caspian Gull (Larus cachinnans), Mediterranean Gull (Larus melanocephalus) and Whiskered Tern (Chlidonias hybrida) are described. These species have regularly bred in Poland since the beginning of the 1990s. The occurrence of super-normal clutches was 1.8%, 4.1% and 0.3% in the Caspian Gull, Mediterranean Gull and Whiskered Tern, respectively. The first descriptions of a female-female pair in the above species as well as in the Yellow-legged Gull (Larus michahellis) and an unusual mixed female-female pair of two gull species (Yellow-legged Gull and Caspian Gull), never mentioned in the literature before, are also presented. The first fully documented case of a multi-female association of the Mediterranean Gull was also identified. The frequency of the SNCs in this study was higher than in other colonies located in different parts of the geographical range of the species.