We documented nest habitat selection, nests success, and factors affecting nest success of Black Terns (Chlidonias niger) at Agassiz National Wildlife Refuge in northwestern Minnesota. During 1992-1994, 289 Black Tern nest sites and 400 random sites were sampled on five search areas totaling 1,325 ha. Four habitat characteristics were measured at each nest and random site: (1) mean water depth, (2) distance to open water, (3) dominant vegetation within a 2-m radius, and (4) amount of open water within a 2-m radius. Habitat variables were highly correlated with each other, making it difficult to estimate independent effects of each habitat variable on nest-site selection. However, conditional logistic regression models indicated that locations closer to open water and in deeper water were more likely to be associated with nest sites. Locations in bulrush (Scirpus acutus) and sedge/grass were preferred, although 68% of nests were in cattail (Typha spp.) reflecting the greater availability of that habitat in the study area. Nest success ranged from 48-69% (Apparent) and 33-62% (Mayfield) among years. Except for five nests that were abandoned or had infertile eggs, nests that failed to hatch apparently were depredated. Nest success was higher for nests with larger clutch sizes and for nests located farther away from other nests. Nests with 3-egg clutches were 2.8 times as likely to hatch as 2-egg nests. The odds of a nest being successful increased by 25% for each 5 m increase in distance to the nearest nest. Earlier nests were also more successful (the odds of a nest being successful was estimated to decrease 7% for each additional day that passed before the nest was initiated). Nest success was not related to nest cluster size and was negatively related to habitat factors associated with nest site-selection.

Knowledge of the ontogeny of the sex ratio is required for proper framing of evolutionary hypotheses regarding adaptive parental sex allocation, competition for mates, evolution of mating systems, and endangered species management. We traced the development of a male-biased adult sex ratio in Nazca Boobies (Sula granti) by determination of the sex ratio at hatching, fledging, and at returning to join the adult population. The sex ratio at hatching and fledging did not differ from unity, while the return sex ratio was significantly male-biased. Therefore, the observed adult sex ratio bias arises after the period of parental care ends, during the subadult/juvenile stage, with important implications for mate competition.

Colonial seabirds such as alcids often do not rapidly recolonize former breeding habitat following extirpation of nesting colonies. Social attraction (e.g., use of decoys, recorded vocalizations and mirrors) artificially stimulates nesting by providing social cues that encourage colonization. Common Murres (Uria aalge) stopped breeding at Devil’s Slide Rock, San Mateo County, California following the 1986 Apex Houston oil spill. Natural recolonization did not occur between 1987 and 1995. Common Murres began regular visits to Devil’s Slide Rock within 24 hours of social attraction equipment installation in January 1996 and six pairs nested by June 1996. Over 90% of murre observations were in decoy plots in contrast to control plots and outside of plots where few murre observations occurred. Significantly more murre presences versus absences were recorded in low density decoy plots and these birds most often frequented open areas (aisles) within decoy clusters. Significantly larger groups of murres visited high density decoy plots and aisle sub-plots. Murre densities were significantly greater within 30 cm of mirrors. Five of six nests were within 60 cm of mirrors. Nests coincided with areas where prior nesting and last pre-1996 attendance had been concentrated. Rapid breeding response combined with recent nonbreeding attendance suggests that the first colonists may have been surviving breeders from the original colony or young produced at the rock prior to the oil spill. The initial recolonization event and continued restoration efforts have prompted further colony growth to 190 pairs nesting by 2004. This study suggests that social stimuli can limit natural colonization of otherwise suitable habitat.

Gull predation is an important source of egg and chick mortality for many seabirds. From 2003-2005, the effects of gull predation and a predator control program on tern nesting success were studied at Eastern Egg Rock, Maine. In 2003, gull predation was uncontrolled, and in 2004 and 2005, attempts were made to shoot Herring (Larus argentatus), Great Black-backed (L. marinus), and Laughing (L. atricilla) gulls that preyed on Common (Sterna hirundo), Arctic (S. paradisaea), and Roseate (S. dougallii) tern adults, eggs, and chicks. To evaluate the effectiveness of gull removal, daily watches were performed from an observation tower and tern hatching and fledging success were measured annually. Despite shooting efforts in 2004-2005, many known predators could not be removed. Great Black-backed Gull predation was a function of year, tidal state, and visibility, while Herring Gull predation depended only on the stage of the tern breeding cycle. Using disappearance of eggs and chicks from monitored nests as a proxy for gull predation pressure, an estimated 23% of Common, 32% of Arctic, and 6% of Roseate tern nests were depredated by gulls during the study period. Predation risk depended on nest position within the colony, but not year, with some areas consistently more vulnerable to gulls than others. We discuss the difficulty of removing predatory gulls from a tern colony lacking nesting Herring and Great Black-backed gulls and suggest the importance of human presence and associated research activities for reducing gull predation at this site.

We analyzed temporal and spatial trends in annual nest counts of Brown Pelicans (Pelecanus occidentalis), Royal Terns (Sterna maxima), and Sandwich Terns (Sterna sandvicensis) throughout South Carolina from 1969 through 2005. There was an increase in the number of active pelican nests from 1969 through the mid 1980s, although this was followed by a steady decline that continued through 2005. Numbers of Royal Tern nests have declined during the study period, especially since 1990. In contrast, annual counts of active Sandwich Tern nests remained relatively stable through the mid 1980s, then increased substantially and have since remained stable. During the early years of the study, a greater proportion of nests from each species occurred on colonies within the Cape Romain region, although this distribution appears to have shifted with a greater proportion of nests now occurring along the southern coast. At the statewide level and at each of the primary colonies, we observed a positive correlation in counts of Brown Pelican and Royal Tern nests. Mechanisms underlying the observed trends are unclear. We suggest that priorities for research include (1) determination of diet and foraging locales for all three species, (2) impacts of ectoparasites on condition and survival of pelican chicks, and (3) metapopulation structure of all three species. Management activities should focus primarily on protection of colony sites.

Studies using stable-isotope analyses of feathers to determine molt locations in marine birds are increasingly common but generally lack verification through ground-truthing. In this study, we examined the stable isotope compositions of wing feathers from King Eiders (Somateria spectabilis) implanted with satellite-transmitters. We compared stable carbon, nitrogen, and hydrogen isotope compositions (δ¹³C, δ¹⁵N, and δD, respectively) of primary feathers with the geographic location of wing molt in the subsequent year. Longitude of molt locations of eiders was highly correlated with δ¹³C (r² = 0.69, N = 12) and δD (r² = 0.90, N = 12) isotope values from their primary feathers grown in the previous year. There was no relationship between δ¹⁵N and location of wing molt (r² = 0.007, N = 12). The results of this study provide further evidence for site fidelity during wing molt by King Eiders.

We report an unusually high return rate (16%) of one-year-old Roseate Terns (Sterna dougallii) to their natal colony on Aride Island, Seychelles, in 2005. Detailed accounts of these birds are provided in terms of timing of arrival, breeding status, and plumage characteristics, and compared with those of two other age classes (2-year-olds and 3 to 6 year-olds) in the same colony and with temperate populations. One-year-old individuals returned on average three weeks later than older birds and did not attempt to breed. Their immature plumage dress (‘portlandica phase’) differed from their one-year-old temperate counterparts, with most birds showing several characteristics of adults in full breeding plumage, such as red bill and red legs, long tail-streamers, and absence of a dark carpal bar. Contrary to expectations from temperate studies, nonbreeding two-year-old individuals did not retain any characteristic of the portlandica plumage, and were virtually inseparable from breeding adults. The ad hoc return rate of Roseate Tern one-year-olds found in this particular year is high compared to recapture/resighting data from colonies in temperate areas, but is comparable to observations made at other tropical (Caribbean) breeding colonies. Altogether, these findings suggest that tropical Roseate Terns are prone to return to their natal site earlier than their temperate counterparts, and show a more rapid acquisition of the adult plumage. This may be especially the case in years of good food supply conditions, since the 2005 event coincided with the two years (2004-2005) of highest marine productivity recorded in the vicinity of Aride Island over the 1997-2005 period.

Geographic variation in the body mass and acoustic parameters of territorial ‘yodels’ recorded from male Common Loons (Gavia immer) were assessed for individuals breeding on territories across the eastern United States. Multivariate analyses incorporating male body mass, body size, the acoustic parameters of yodels, and geographic latitude and longitude indicated that males inhabiting lakes in northwestern regions were smaller and produced higher-frequency yodels. These relationships strengthen previous observations of clinal geographic variation in loon body size and vocal behavior across North America, but also support the hypothesis that the dominant frequencies of yodels are in part influenced by male body size. Therefore, the frequencies loons use for long-distance communication are apparently influenced, at least in part, by those selective forces responsible for shaping optimal body size.

Annual apparent survival rates of the Magnificent Frigatebird (Fregata magnificens) were estimated from 1998 to 2003 using a capture-resight model with 870 marked adult birds on Isla Isabel, México (21°51’N, 105°54’W). The most parsimonious model was a time since marking model (or two age class model) with constant resighting rate for males and females (p_m and p_f), constant apparent survival rate for males in both age classes (ϕ¹_m and ϕ² _m), and time-dependent apparent survival rate for females (ϕ¹_f and ϕ² _f) in both age classes. We found higher resighting rates in males than in females, a tendency of higher apparent survival in females than in males in 1999, a clear higher apparent survival rates in females than in males in 2000, nearest the same apparent survival rates of the two age classes of males throughout, and differences in apparent survival between age classes of females showing considerable annual variation within age classes. The results suggest permanent emigration of females from the breeding colony, whereas males showed site fidelity.

From 26 March to 2 August 2003, both the time budget and the diurnal rhythm of behavior of breeding Black-necked Cranes (Grus nigricollis) were studied at Ruoergai Wetlands National Natural Reserve, Sichuan Province, China. The breeding season was divided into three phases: Pre-reproduction, Incubation and Chick-rearing periods. Foraging behavior was the most prevalent during the breeding season, accounting for 45% of the diurnal time budget, followed by breeding activity (28%), locomotion (10%), maintenance (9%), alert (7%), resting (1%) and “other behavior” including excretion, calling and antagonism (0.6%). During the three breeding phases, there were significant differences in the time budget of all behavior types except for locomotion and “other behavior”. In terms of frequency of events, alert behavior was the highest, occurring 43 times per hour, followed by foraging (31), maintenance (17), locomotion (11), breeding activity (5), “other behavior” (1) and resting (0.7). During the three breeding phases, there were significant differences in the frequency of various behavior types except for “other behavior”. During the day, the rhythm of different behavior types varied according to time.

The Black-faced Spoonbill (Platalea minor) is a critically endangered species. Over 50% of individuals winter regularly in Chiku Wetland on the southwestern coast of Taiwan. This study investigated the stomach contents of the Black-faced Spoonbills killed by avian botulism between December 2002 and January 2003 to identify diet of this species at the wintering site. Fourteen fish species belonging to eight families and one species of prawn were retrieved from 43 stomachs. The Shannon-Weiner index for the diet was 1.90. Estimated mean total dry weight of contents per stomach containing animal items was 23.3 g (0.1-111.7 g). Dogtooth-toxic Goby (Yongeichthys caninus) was the most abundant diet species comprising 39% of the total diet items but contributed only 2% of the estimated total dry weight. Large-scale Mullet (Liza macrolepis), comprising only 17% of the total diet items but contributed 54% of the estimated total dry weight, was the most important diet species. Our results suggest that conservation of the Large-scale Mullet is important to this endangered wader.

We examined sexual dimorphism of Dovekie (Alle alle) from the breeding colony in Hornsund (south Spitsbergen). Each bird was sexed using DNA extracted from blood. Body morphometrics including flattened wing, head-bill, tarsus length, bill width and body mass were recorded in 331 birds caught during the breeding season in 2003-2006. Analysis of measurements of mated pairs showed that males are usually bigger than females in case of head-bill length, bill width and body mass. Only head-bill length was significantly correlated within a pair (r₆₉ = 0.354, P < 0.005). A forward stepwise discriminant function analysis (DFA) was used to evaluate sexual size dimorphism in Dovekie. The first function, applied to 4 measurements, identified head-bill length and bill width as the best measurements for sexing and correctly classified 70% of our sample (but only 38% better than chance). The second function, which was applied to only 3 parameters (excluding bill width), identified head-bill length as the best measurement for sexing and correctly classified 65% of our sample (30% better than chance). In Dovekie, a species having a high degree of overlap between the sexes, discriminant function should be used with caution. It is recommended that a combination of morphometrics, behavior observation and genetic analysis be used to obtain the highest accuracy in sexing individuals correctly.

The Imperial Shag (Phalacrocorax atriceps) is monomorphic in plumage, but males are larger than females. We analyzed the sexual size dimorphism and variability of six morphometric characteristics (bill length, bill depth, head length, tarsus length, wing length, and body mass) measured on 291 breeding Imperial Shags at Punta León colony in coastal Patagonia, Argentina, during 2004 and 2005 breeding seasons. Discriminant analyses were performed on external measurements that we considered potentially useful in sexing Imperial Shags. All the birds were sexed by a distinctive behavior (vocalizations) and a sub sample of fifty were also sexed by DNA-based genetic techniques, showing 100% agreement between the two methods. All measured characteristics differed between the sexes, with males being larger than females. Body mass (17.8-18.0%) and bill depth (12.8-13.2%) showed the highest level of dimorphism whereas bill, head, tarsus, and wing length were less dimorphic (ranging 4.8-6.0%). Dimorphism in body mass for breeding shags was lower than previously reported during winter, prior to the breeding season. Although the wing length showed the lowest degree of dimorphism (5.3-5.4%), it presented the lowest coefficient of variation (1.9-2.0%) resulting in the most accurate single-measurement indicating sex. A cross validation process with a new sample, revealed that discriminant functions comprised by two characteristics were more accurate and reliable for sex determination than single-measurements. We obtained two functions correctly classifying 94-97% of shags. These functions were reliable (similar accuracy for discriminant analysis, Jackknifed validation, and cross-validation with a new sample) and seasonal unbiased, as body mass was not included in the analysis.

Diet of the Great Cormorant (Phalacrocorax carbo) was studied in three coastal wintering areas (Axios and Evros Deltas, Messolonghi Lagoon) of Greece, in order to assess spatial differences and commercial value of prey. Thirteen birds were collected from the Axios Delta, 28 from the Evros Delta, and 16 from Messolonghi Lagoon. Pellets were collected from the Evros Delta (26) and Messolonghi Lagoon (30). A variety of fish taxa were found in the samples, but only one or two dominated in Great Cormorant’s diet, either by numbers or biomass. Grey mullets (Mugilidae and Golden Grey Mullet Liza aurata) were the most important prey by numbers and biomass in the Axios Delta; Giebel (Carassius auratus gibelio) dominated by numbers and biomass in the Evros Delta; whereas Boyer’s Sand Smelt (Atherina boyeri) was most important by numbers and Mugilidae by biomass at Messolonghi Lagoon. Differences found in diet between areas are probably due to differences in prey species composition and abundance. Fish of high commercial value contributed in low proportions in Great Cormorant’s diet, by numbers and biomass, being highest at Messolonghi Lagoon (22.4% by numbers, pellets; 11.5% by biomass, stomachs). The small overlap between the bird’s diet and valuable prey suggests minimal competition with fisheries.

Jehl (1988) observed that the departure of Eared Grebes Podiceps nigricollis from Mono Lake, California, a major fall staging area, did not occur in relation to time of year or weather but was initiated after the density of brine shrimp (Artemia monica)-the major prey-fell below a predictable threshold. Although Caudell and Conover (2006) found no such relationship at Great Salt Lake, the other major staging area, reevaluation of their data indicates that the threshold concept applies there as well. Substantial differences in the staging ecology of Eared Grebes at the two lakes remain to be demonstrated.

Techniques most commonly used to estimate migratory shorebird abundance often yield estimates with a wide margin of error, and fail to consider extent of habitat use. This study was designed to investigate whether observation of percentage of a given area covered by shorebird footprints may be useful in obtaining accurate estimates of habitat use. Flocks of Semipalmated Sandpipers (Calidris pusilla) foraging on mudflats in the upper Bay of Fundy, Canada, were videotaped and percent-cover by footprints was observed upon their departure. Through review of the videotapes, habitat use was determined in bird-seconds m^-2 (sum of time each individual was present divided by the area observed). There was a strong positive, non-linear relationship between percent-cover and habitat use, which suggests that the former can be used to estimate the latter. A theoretical value for habitat use resulting in 100% footprint cover, beyond which the method would be ineffective, was calculated. Observed values did not approach this upper limit, and in other related studies 100% cover has rarely been noted, suggesting that this technique is appropriate for use in the Bay of Fundy and in other similar settings.

We determined diurnal time-activity budgets of Mute Swans (Cygnus olor) at Chesapeake Bay, Maryland, USA with the principal aim of determining intensity of their feeding activity. Although Mute Swan herbivory is believed to contribute to declines in submerged aquatic vegetation (SAV) in the Bay, there is a lack of comprehensive quantitative data indicating the magnitude of feeding activity by Mute Swans. We collected time-activity budgets from May through August 2003 (N = 50 10-minute observation periods) and from March through August 2004 (N = 818). Mute Swans spent more time feeding (38.4%) than in non-foraging activities, including swimming (21.8%), resting (18.4%), self-maintenance (18.6%), agonistic activity (1.7%), and disturbance-induced activities (1.2%). Feeding intensity was not influenced by seasons (spring and summer). Mute Swans foraged more actively during the morning than they did midday. Mute Swans in flocks ( three individuals) spent more time feeding than those in pairs and birds in larger flocks spent more time feeding than those in smaller flocks. Moreover, a recent exclosure study on the Chesapeake Bay indicated that grazing by Mute Swan flocks caused a higher SAV decline than grazing by paired Mute Swans. It is likely that individuals in flocks (especially large ones) pose a greater risk to the SAV in the Bay as compared to those in pairs. Thus, management authorities should seriously consider controlling Mute Swan flocks (especially large ones) in the Bay in addition to pairs.

We studied the breeding ecology of Black-crowned Night Herons (Nycticorax nycticorax) in three mixed species heronries in Pyeongtaek, Gyeonggi-Do, Korea during 2000 and 2001. Population size and breeding species changed between 2000 and 2001. Mean clutch size, hatching success and fledging success was not significantly different between years. Fledging success varied significantly in 2000 but not in 2001 with regard to number of hatchlings per nest. Mass, culmen-length, and wing-length growth rates of Black-crowned Night Heron chicks did not differ between years. With regard to hatching order in 2000 and in 2001, only tarsus-length growth rates differed between years. Clutch size, reproductive success, and growth rate of Black-crowned Night Herons did not differ between years.

The reproductive biology of the Coot (Fulica atra) was studied in a shallow pond, Timerganine, in the semi-arid Hauts-Plateaux. Our results contrast with a previous study carried out in the coastal wetlands of Numidia showing differences in laying dates, egg size and clutch size. Nest site selection was strongly influenced by spatial patch structure and vegetation structure may act as a cue of habitat quality. Coots bred at Timerganine at a high nest density and reproductive performances were influenced by adverse weather and more markedly by both predation and anthropogenic activities. We also found that alternative reproductive strategies were present within the studied coot population which exhibited a high rate of conspecific brood parasitism.

Great Crested Grebes (Podiceps cristatus), especially when nesting in large colonies, are known to suffer huge egg losses during storms. However, if the devastation of nests is not complete, partial or entire clutches can still be saved. The effects of high waves and strong wind can be countered to some extent by continuous and accelerated building. Even eggs floating in the water inside the remains of destroyed platforms may be recuperated by rebuilding the nest around and pushing the eggs with the beak ever higher on the weed. Due to the high resistance of eggs to cooling, they may even hatch after having passed several hours in cold water. In addition, grebes are capable to resume or continue laying quickly to replace lost eggs.

Black-headed Gulls (Larus ridibundus) were caught on the southern Baltic coast during early phase of their autumn migration between 27 July and 9 August from 1992 to 1995. Due to involvement in breeding, adult Black-headed Gull started primary replacement later than second-year birds, but their molt was slightly faster during the studied two-week period. This suggests that the difference in primary molt score between the age classes may decrease toward the end of the molt period. There were no differences in primary molt between sexes. Adults had larger hole in wing area and they had higher body condition index than second-year birds. This might reflect higher cost of flight of adults due to their lower aerodynamic efficiency of the wing and their tendency to buffer themselves against increased energetic stress. Second-year Black-headed Gulls migrate for longer distances farther than adults on average and this might be a reason of their slower rate of primary replacement.

A non-breeding adult female White Ibis (Eudocimus albus) was observed tending multiple nests during the 2006 wading bird breeding season in the Florida Everglades. This is the first known case of adult multiple nest-attending breeding behavior documented for the Ciconiiformes order.

The brood size of the White Stork (Ciconia ciconia) was investigated at 30 localities within the breeding range of the species in Greece in 1993, 1994 and 1995. These localities were grouped in four major habitat types: river, lake, delta and dry habitat (lacking water bodies nearby). Brood size groups of 1, 2, and 5 nestlings (less common) and 3-4 nestlings (common) for all years and major habitats were compared. No significant spatial or temporal differences in the brood sizes were found. The mean brood size of the White Stork in Greece was among the highest in Europe attributable to favorable feeding conditions associated with cultivations.

Data were collected at one of the important stop-over sites in the southern Baltic between 1989 and 1995. Sandwich Terns were not only more advanced in primary molt than Common Terns, but also replaced their flight feathers faster due to larger number of primaries growing simultaneously. All caught adult Sandwich Terns were in active molt, whereas over 21% Common Terns either had not started primary molt or suspended it. The difference in migration strategy may be the main reason for the discrepancy between these two species in molt advancement. Biometrical analysis showed that juveniles of both species did not reach adult size at this stage of migration. Sandwich Terns caught in late summer in northeast England had shorter wings than birds from Puck Bay probably due to different origin of birds caught at these two sites. Common Terns caught in Puck Bay were larger than birds from German and Scottish breeding colonies and also from birds measured in northeast England. Moreover in Puck Bay, 84% of Common Terns were replacing primaries during autumn migration, whereas only 45% in Teesmouth did it at the same time. It seems that Common Terns from west Europe and terns passing the Baltic Sea belong to different populations, which differ in the distance they cross between breeding and wintering grounds and also in biometrics.