This study describes qualitatively and quantitatively the kleptoparasitic behavior of the Brown-hooded Gull (Larus maculipennis) and Grey-hooded Gull (Larus cirrocephalus) on the American Oystercatcher (Haematopus palliatus), and considers the influence of environmental variables on the occurrence and success of the kleptoparasitism. Focal and scan samplings were performed, recording a total of 358 kleptoparasitic attempts. The overall occurrence rate was 1.2 ± 1.3 attempts per 5 min., of which 42% of attempts were successful. All kleptoparasitic attempts were performed when oystercatchers were feeding on Stout Razor Clams (Tagellus plebeius). Gulls stole food from Oystercatchers by two kleptoparasitic tactics; running (used in 40% of cases) and flying (used in 60% of cases). A significant difference in the rate of success of kleptoparasitism and an increase in the use of flying kleptoparasitism were observed under windy conditions. Gulls showed limited ability to open clams by themselves, and never swallowed whole clams. Kleptoparasitic attacks occurred within three seconds of the clam being ingested by the host, indicating the accurate kleptoparasitic skills of hooded gulls. Possible factors that affected the decisions taken by gulls about when and how to start the robbing behavior are discussed. Features of the kleptoparasitic behavior performed by hooded gulls on oystercatchers provide some relevant questions regarding the “generalist” or “specialist” character of these parasites.

The δ¹³C, δ¹⁵N, and δ³⁴S stable isotopic values of feathers from pre-fledged Laughing Gulls (Larus atricilla) in coastal Virginia and Jamaica Bay, New York were used to examine dietary variation during the nestling period. The tip portions of the feathers were used to indicate diet during the initiation of primary feather growth, whereas the base portions indicated diet during the period immediately prior to fledging. The results indicate that diets of the nestlings in Virginia moved to a higher trophic level during the period prior to fledging, however the New York nestlings did not appear to undergo any appreciable dietary change during this period. Overall, nestlings from both colonies consumed proportionately more foods of marine origin than freshwater or terrestrial. Therefore, the results do not support those of earlier studies that suggested that partially developed salt glands in young gulls might restrict the diet to more terrestrial or freshwater prey in the early stages of nestling growth.

We studied the diet of the Common Tern (Sterna hirundo) in several islands of the Azores during 1994, based on the analysis of 777 food pellets. The diet of Common Terns was based on a few species of small pelagic fish. Trumpet Fish (Macroramphosus spp.) dominated the diet in terms of both frequency of occurrence (84%) and numerical frequency (69%). This species, together with Boarfish (Capros aper), Blue Jack Mackerel (Trachurus picturatus) and lantern fish (Families Myctophidae, Sternoptychidae, Diretmidae), accounted for more than 96% of the prey taken by Common Terns on all the islands. Insects occurred in 10% of all pellets analyzed and were present in almost 15% of the pellets from Corvo. Lantern fish represented an important fraction of the diet of Common Terns in the Azores and included several species previously undescribed as prey of seabirds in the region. Comparisons with dietary data obtained in subsequent years showed little inter-annual variability in the frequency of abundance of the main prey species, except for the lantern fish, which exhibited a higher frequency of occurrence in 1995.

Social stimulation in concert with environmental factors may influence the degree of reproductive synchrony among colonial breeders. Synchronous breeding has been shown to enhance reproductive success by decreasing predation. Although Common Murres (Uria aalge) typically have a cyclic pre-lay attendance pattern, during one of four consecutive breeding seasons we observed one acyclic pre-lay period (1999). The present study investigated how differences in pre-lay attendance patterns may influence breeding synchrony and reproductive success in a Common Murre sub-colony on Great Island, Newfoundland. Compared to the cyclic pre-lay period (2000), the acyclic pre-lay period showed: i) less synchronous egg-laying, ii) pairs spent less time together at their site due to the overall lower attendance by both sexes, but particularly by females, and iii) higher predation during early and first half of peak egg-laying, although overall reproductive success did not differ between years due to high re-laying rates. These results suggest that cyclic attendance during the pre-lay period of Common Murres may influence breeding synchrony within a sub-colony, which may reduce predation during early incubation and late chick rearing.

We studied the way, timing and diurnal rhythm of young Atlantic Puffins (Fratercula arctica) leaving colonies in NW Norway and Faeroes. The colonies differed in nesting habitat and predatory pressure. Both adult and young Puffins from Bleiksøy were significantly larger and heavier than those from Nólsoy. Young birds left the Bleiksøy colony about ten days later in the season, but considerably earlier during the night (22.00-04.00 h; peak: 00.00-01.00 h) than those on Nólsoy (24.00-0600 h; peak: 02.00-03.00 h). The fledging period was more synchronized on Bleiksøy, both within the season and on particular nights. Body mass and size of young puffins leaving the colony tended to decrease through the fledging period. Well-developed young birds from sloping parts of the Bleik colony flew down to the sea, while those from the lower-lying, flatter parts of the colony and those in poor condition walked to the sea. Fledglings which left on the wing reached the sea about one hour earlier and could fly beyond the inshore waters before daybreak, thus avoiding the risk of gull predation. They were more numerous during the first six days of the 10-day fledging period and were larger than those, which left on foot. The latter lost much time and energy overcoming dense vegetation, boulders and the tidal zone on their way to the open sea. As a result, they were still near the shore at dawn, in the zone intensively penetrated by predators. We suggest that predatory pressure of the big gulls, which are numerous on Bleiksøy but almost absent from Nólsoy, could have a significant impact on timing of fledging of their prey.

Global warming is expected to result in an acceleration in current rates of sea level rise, inundating many low-lying coastal and intertidal areas. This could have important implications for organisms that depend on these sites, including shorebirds that rely on them for feeding habitat during their migrations and in winter. We modeled the potential changes in the extent of intertidal foraging habitat for shorebirds at five sites in the United States that currently support internationally important numbers of migrating and wintering birds. Even assuming a conservative global warming scenario of 2°C within the next century (the most recent projections range between 1.4°C and 5.8°C), we project major intertidal habitat loss at four of the sites (Willapa Bay, Humboldt Bay, San Francisco Bay, and Delaware Bay). Projected losses range between 20% and 70% of current intertidal habitat. Such losses might jeopardize the ability of these sites to continue to support their current shorebird numbers. The most severe losses are likely to occur at sites where the coastline is unable to move inland because of steep topography or seawalls. The effects of sea level rise may be exacerbated by additional anthropogenic factors. In southern San Francisco Bay, for example, sea level rise may interact with land subsidence due to aquifer depletion, and the constraints imposed by existing seawalls on the landward migration of habitat, resulting in the greatest habitat loss. At the fifth site (Bolivar Flats) we project smaller losses as the intertidal habitats are unconstrained by sea walls and will be able to migrate inland in response to rising sea level. Installation of additional coastal protection barriers at this site and others is likely to exacerbate the rate and extent of intertidal habitat loss.

High levels of egg predation by numerous vertebrates has been implicated as a limiting factor in many avian populations. In response, ornithologists often attempt to control potential egg predators through lethal methods or large scale fencing of breeding habitat. More recently, individual nest exclosures have been employed to deter egg predators. During 1999 and 2000, we experimentally tested nest exclosure effectiveness at enhancing Killdeer (Charadrius vociferus) nest success in the Great Basin, USA. We demonstrated that nests with exclosures had significantly lower daily mortality rates compared to nests without exclosures. Although nest exclosures increased Killdeer nest success in this study, it is necessary to identify predators impacting nest success prior to the exclosure design. Nest exclosures are unlikely to be equally successful among sites, and variation in exclosure design may be required across both the range of a species and/or breeding seasons at a single site. The exclosure design we used did not deter small mammals and birds, or reptiles; and we observed small mustelids killing incubating birds. However, these exclosures were effective at increasing hatching success by deterring larger predators (ravens, gulls, canids). Any benefit derived from the nest exclosure used may potentially be offset by increased predation on incubating adults. Nest exclosures are not a means of preserving biological diversity over geologic time, but rather a potential temporary site-specific tool that increases nest success while long-term conservation plans are developed.

Coordinated waterbird counts have been carried out in major Kenyan wetlands annually over the last decade. The lakes of Naivasha, Elmenteita, Nakuru (counted since 1991) and Bogoria are close to each other in the southern Rift Valley and hold the bulk of both resident and migrant waterbirds counted each year. Levels of the four lakes fluctuate substantially and all but Naivasha are saline. By contrast, Dandora Ponds near Nairobi is a site with stable water levels. We compared trends in numbers of birds, categorized by family and by migratory status, with an earlier analysis in 1996 and between the fluctuating Rift Valley lakes and Dandora Ponds. Flamingo numbers remained highly variable at all sites, showing no long-term trends. In 1996, significant declines were found in many piscivorous waterbird groups, including grebes, pelicans, cormorants, storks, terns and gulls, mainly associated with falling lake levels at Lake Nakuru; by 2000, numbers had recovered. Consistent declines in rallids, birds of prey and kingfishers were evident in 1996, mainly due to falling numbers at Lake Naivasha. By 2000, kingfisher numbers had fully, and raptor numbers had partially, recovered. Rallids, mainly Red-knobbed Coot (Fulica cristata), continued to decline sharply through 1998, but recovered slightly to 1996 levels by 2000. After notably high numbers in 1996-1999, Palaearctic ducks declined dramatically in 2000 to a ten-year low. With the exception of rallids, none of the groups that had declined from 1991-1996 showed any trend in numbers over the extended time period. At Dandora, numbers of most waterbird groups fluctuated substantially despite constant conditions. The fluctuations showed little synchrony with between species or with those at the southern Rift Valley lakes, suggesting waterbirds were responding to the availability of suitable wetlands over a large area. The declines from 1991-1996 in the southern Rift Valley were temporary; recoveries in waterbird numbers were not attributable to improved environmental management (human pressures on these wetlands intensified from 1997-2000), but to higher lake levels in 1997/98. The ten-year data set covers a full cycle of low and high lake levels, which the six-year dataset did not, and may now form an adequate baseline for monitoring.

We present the first detailed information on breeding marine birds from the southern Lagoon of New Caledonia, southwest Pacific. The area under consideration, 5,000 km², hosts 74 islets varying in size from ca. 0.05 to 30 ha. We found 13 breeding seabird species, of the 23 known to breed in the New Caledonian region. The most significant seabird numbers included large colonies of Black Noddy (Anous minutus, 50,000-100,000 pairs) and especially Wedge-tailed Shearwaters (Puffinus pacificus); the latter species totaling half a million pairs and probably the largest colony in the world. About 5,000 pairs of Roseate Tern (Sterna dougalli) have been found. Several species of conservation concern are also breeding in appreciable numbers, e.g., Fairy Tern (Sterna nereis) and Tahiti Petrel (Pseudobulweria rostrata); both New Caledonian endemic subspecies. However, some species are now very rare (e.g., Red-footed Booby Sula sula), and others have appreciably declined over the last eight years (Fairy Tern, Black-naped Tern Sterna sumatrana and Crested Tern S. bergii). The recent increase in the frequency of visits to islets by people from Nouméa (ca.100,000 inhabitants), resulting from the increase in the number of leisure boats, may be the principal factor responsible for the current trends and threats. Human disturbance seems to be a major threat that may lead to desertion of seabirds on islets, or reduced breeding success.

The nesting ecology of the Greater Adjutant Stork (Leptoptilos dubius), the rarest stork in the world, was studied in the Brahmaputra Valley, Assam, India during 1994-97. We made a study of nine colonies in the valley during the 1994-95 nesting season, followed by a more intensive study in two subsequent nesting seasons (1995-96 and 1996-97) of two colonies at Nagaon, in central Assam. We measured the dimensions of both nest and non-nest trees, nearest distance between nest trees, and nearest house, nearest forest, nearest road, nearest water source and nearest foraging ground from each colony. All of the colonies were near human settlements. The structure of nest trees differed significantly from non-nest trees in both the overall and the intensive studies. Number of nests was highly correlated with tree height, diameter at breast height (DBH) and canopy area. About 90% of nests were built on the top of the canopy. Storks preferred to nest in compact colonies on large, widely branched trees with thin foliage cover and nearby food sources.

We report on the breeding of several individuals of Atlantic Cory’s Shearwater (Calonectris diomedea borealis) in a small colony of Mediterranean Cory’s Shearwater (C. d. diomedea) in the western Mediterranean (Columbretes Islands, northeastern Spain). We briefly discuss the potential role of Atlantic Cory’s Shearwaters in gene flow at small and declining Mediterranean colonies.

We describe the distribution and estimate the density of the Flightless Steamer Duck (Tachyeres pteneres) and the Kelp Goose (Chloephaga hybrida) along the Beagle Channel, Tierra del Fuego, during the summer season (February and March) 1997. Using a 10-min transects method from a vessel; we estimated density and evaluated its relation with different characteristics of habitats. The study area was divided a priori into six zones. Due to the scarcity of information about these species, we reviewed previous literature to evaluate seasonal movements and made comparisons with other regions of Tierra del Fuego. Differences in habitat distribution compared with the previous studies in the same area are reported. In the Beagle Channel, the Flightless Steamer Duck was more abundant than the Kelp Goose. The observed distribution seems to be a result of a preference for the inner waters of the Beagle Channel, at the western sector of the study area. In spite of the difference in the distribution of the two waterfowl, both preferred similar habitats. The preferred habitat was protected coasts such as small bays, inlets, or sectors of the islands sheltered from the prevailing winds and currents. The geese moved during autumn and winter from the Beagle Channel and Staten Island to the Atlantic coast. In terms of difference in density between areas, the Kelp Geese were twenty times more frequent in Staten Island than around the Beagle Channel, while Flightless Steamer Duck were twice as dense in Staten Island than the Beagle Channel.

In keeping with many species of waterbirds, there is little difference in the body size or external appearance of adult male and female Northern Gannets (Morus bassanus). Previous work has indicated that some morphological characteristics and behavioral patterns differ on average between sexes but there has yet to be a quantitative evaluation of the accuracy or applicability of these different criteria in determining sex. The aim of this study was to use DNA-based techniques to determine the sexes of adults and to use this information to evaluate a range of behavioral and morphological criteria for sex determination. Nape-biting behavior was frequently observed, was performed almost exclusively (>99% of observations) by males and was completely accurate in assigning sexes on the basis of multiple observations at each nest: this confirms previous results which indicated that nape-biting is highly sex-specific. Collection of nest material was also performed primarily by males, but this seldom occurred and so despite over 500 h of observations at each nest, fewer than 30% of pairs were sexed correctly using this criterion. Only two-thirds of birds were sexed correctly from head plumage color and fewer than 30% from foot web-line color. Behavioral observations were as accurate as DNA-based sexing and more effective than morphology for sexing adult birds at all stages of chick rearing.

Nesting in association with species that aggressively attack predators may reduce nest predation in some birds. For example, nesting ducks sometimes benefit from aggressive defence by nesting Canada Geese (Branta canadensis). Although Common Eiders (Somateria mollissima) commonly nest with gulls (Larus spp.), the costs and benefits for eiders of this association remain uncertain. Over two years, 32 instances of kleptoparasitism of Herring Gulls (Larus argentatus) by Canada Geese were recorded in arctic Canada. The Canada Geese nested amongst Common Eiders and interrupted Herring Gulls while taking eider eggs. The geese displaced Herring Gulls from approximately ten percent of all eider eggs taken from nests, and ate egg contents themselves. Kleptoparasitism may provide Canada Geese with an important exogenous food resource, but the small overall number of eggs stolen from gulls (less than five percent of all eider eggs laid) limits the potential consequences of additive compensatory predation pressure by gulls within the eider colony.

Between October 1999 and April 2000, we surveyed the waterbirds at Lake Lashihai, China. A total of 52 species were recorded, of which one species was a resident, 34 were winter visitors, and 17 were passage migrants. Species richness was highest in November. Passage migrants mainly occurred in October, November, and April, and they stayed longer at the lake during their autumn migration than during the spring migration. The seasonal distribution pattern of total numbers of all waterbirds was bimodal. One peak occurred between late December and early January, and the other in middle March. The seasonal distribution patterns of 15 common species have been classified as bimodal, unimodal, or irregular. The numbers of five common species were variable in middle winter, and their numerical change in contiguous weeks were more than 30%, suggesting that local movements might be frequent.

Early attempts to identify sex in sexually monomorphic birds were based on morphological or chromosomal characters but since avian W-specific DNA sequences were identified, their PCR amplification has become commonly used molecular sexing method. We report here a DNA technique that amplifies an intrinsic CHD region without a DNA extraction. This test was applied to twelve species belonging to three waterbird orders, Ciconiiformes, Pelecaniformes and Phoenicopteriformes. All birds were sexed successfully with high reproducibility. There was complete agreement between our results and sex diagnosis by parallel methods. Because the proposed method eliminates the DNA extraction step, this protocol is more efficient and simple. It demands only minute amounts of DNA and reduces both time and the quantities of reagents consumed.

We evaluated the basal metabolic rate (BMR), thermal conductance (C_m), and lower critical temperature (T_lc) of Leach’s Storm-petrel (Oceanodroma leucorhoa) using open-flow respirometry. Measurements were taken from six adults collected at their nests at Great Island, Witless Bay Ecological Reserve, Newfoundland, Canada. In order to establish T_lc and C_m, we determined rates of oxygen consumption after exposing birds to different ambient temperatures (10°C, 20°C, 26°C, and 30°C). Storm-petrels had a minimal C_m of 0.122 ± 0.019 ml O₂/g·°C·h and T_lc was 24°C. The basal rate of oxygen consumption was 1.85 ± 0.24 ml O₂/g·h. Incubating Leach’s Storm-petrels had a basal rate of metabolism lower than previously reported for this species. Possible explanations for this discrepancy include the use of different techniques to measure metabolic rates, and the physiological state of the birds being measured. In this respect, our results coupled with those from previous studies, suggest decreased metabolic rates in incubating Procellariformes compared to those of non-reproducing birds measured at the same temperature. This decline in metabolism is possibly related to metabolic depression due to fasting.

The “Incubatory Reserves Constancy” hypothesis asserts that incubation could be a departure from breeding stress that allows for the maintenance or recovery of body reserves after laying effort (females) or territory defense (males) in those species with bi-parental incubation such as gulls. The plasma composition and body mass of incubating Yellow-legged Gulls (Larus cachinnans) were analyzed and related to the number of days after egg-laying. Female gulls showed an increase in uric acid and cholesterol levels, whereas males showed only an increase in uric acid values throughout this period. Moreover, females increased while males maintained their body masses. These results could reflect a recovery process after the laying effort supporting the Incubatory Reserves Constancy hypothesis in females. Uric acid and urea levels are positively correlated to body condition in Yellow-legged Gulls, which could be the result of a change in diet composition. This disagrees with recent findings on body composition in incubating gulls and could be related to variations in food availability among populations or years, and could reflect flexibility in the investment devoted by each sex.