The response of Great Blue Herons (Ardea herodias), Great Egrets (Casmerodius albus), Wood Storks (Mycteria americana), and White Ibises (Eudocimus albus) to water level (index of depth) and vegetation in the northern Everglades of Florida was studied in two years, each with dissimilar water levels. A regression model was constructed for each species in an average year (1988) and a dry year (1989) to examine the relationship of bird abundance to water depth and area of eight vegetation classes. The analyses showed that bird abundance is related to both water level and the vegetation community, but water level generally had the greatest effect. Models showed that in the average year (1988), there was a water level threshold, above which bird abundance was predicted to decline. The level threshold varied among species and may have reflected species-specific foraging constraints. However, in the dry year (1989), the relationship between bird abundance and water level was positive and linear, indicating that few places had water deeper than the thresholds observed in the average year. Overall, the area of slough vegetation appeared to have the second greatest effect on bird abundance. Generally, all models had low coefficients of determination (R² range 0.06-0.42) suggesting that factors other than water level and vegetation were important, or birds were responding to variables in the model, but at different spatial scales than that which the data were collected. Models for Great Blue Herons and Great Egrets had higher coefficients of determination than models for Wood Storks and White Ibises. The more solitary feeding behavior of the herons and egrets resulted in a more even distribution across the marsh than for storks and ibises, which were usually found in flocks. Our study suggests that if restoration of the Everglades results in more natural hydrologic cycles, an increase in the amount of slough habitat, and a decrease in the proportion of cattails, foraging conditions for wading birds may improve.

Nest defense theory interprets the behavior of animals faced with the threat of predation within an optimality framework in which risks to parents are balanced against risks to offspring. We conducted “flights” of a model Peregrine (Falco peregrinus) towards nesting Common Terns (Sterna hirundo). Nesting parameters such as laying date, clutch-size (one to four eggs), and offspring age (fresh eggs to newly-hatched chicks) were known for 57 individual parents, while egg mass (16.5-24.6 g) was known for 50 parents. Age (three to 23 yr) and sex were known for 27 and 41 parents, respectively. We defined nest attentiveness as the number of outflights performed by each bird in the first 15 min after the Peregrine flight. Multivariate analysis showed that high attentiveness was associated with early laying and large eggs, but not with sex of the parents, distance from the predator, nor with clutch-size. Age of parents and age of offspring were less strongly correlated with nest attentiveness, but could not be excluded as explanatory variables. Among existing hypotheses, our results are most consistent with the hypothesis that nest attentiveness should increase with increasing value or quality of offspring. Given that previous studies have shown early laying and large eggs to be indicators of high parental quality in terns, we propose a new hypothesis that the intensity of nest attentiveness also increases with parental quality.

This paper addresses the hypothesis that parental quality, expressed in terms of nest location, determines differences in breeding parameters between colonies and colony areas. I compared hatching date, egg size, egg shape, clutch size, breeding success and chick growth of Roseate Terns (Sterna dougallii) on the tropical Aride Island, Seychelles between: a) central pairs of an old colony, b) peripheral pairs of the same colony, c) pairs of old small sub-colonies and c) pairs of a recently formed colony. The breeding parameters at the small, old colonies were similar to those of the large, old colony and significantly different from those of the new colony, suggesting that parental quality is more closely related to sub-colony age than to sub-colony size. In 1998, a good breeding season, egg size was similar between all study areas, but clutch size in the new colony was significantly larger than that in the center of the old colony and the small sub-colonies. However, breeding success was significantly higher in the last two areas. In 1999, a poor breeding season, center-eggs were smaller than both edge-eggs and new-colony eggs. These patterns at the center of the old and the new colony are the opposite to those described for seabirds in temperate areas. The shape index of eggs in the new colony was lower than that of eggs in the old colony, suggesting that the new colony was formed mainly by young birds. Parameters of early growth and linear growth rate showed only minor differences between study colonies. The earliest breeding birds laid in the center of the old colony, so these results agree with a proposed hypothesis that tropical Roseate Terns trade egg and clutch size for earliness of laying. Therefore, the positive effect of larger egg size on the growth parameters of chicks from the new colony was probably annulled by the opposing effect of other factors such as low parental quality and declining foraging conditions.

Because migration routes and stopover sites of the endangered Palearctic migratory Great White Pelican (Pelecanus onocrotalus) are poorly known, satellite tracking was used to map spring and autumn migration routes, stopover sites and ranging areas in Europe, Israel and Africa. Four immature and one adult individual were equipped with transmitters in Israel. Three of these pelicans did not migrate from Israel during the tracking period. One immature male pelican accomplished two spring migrations to Europe and an autumn migration back to Israel, where it over-wintered. Its northward routes passed through Lebanon, Syria, Turkey and Bulgaria and it arrived at the River Danube after three weeks. This individual’s vast ranging areas in Europe during two consecutive summers included the Aegean Sea, Bulgaria, Greece and Romania, but excluded the Danube River breeding colony. One individual continued its migration to Africa. It reached the Sudd area in southern Sudan after two stops at Lake Nasser and in Jebel Aulia Dam on the White Nile. Its range in Africa included the Sudd, Lake Roseires on the Blue Nile, the lakes of the Ethiopian Great Valley and Lake Rudolf in Kenya. Although this information was obtained from a small number of individuals it is an essential addition to the body of knowledge required in order to establish a protection policy for this migratory species.

The American White Pelican (Pelecanus erythrorhynchos) is a predator on Yellowstone Cutthroat Trout (Oncorhynchus clarki bouvieri) in Yellowstone National Park, Wyoming. This two-year study examined the biotic and abiotic factors that influenced the spatial patterns and temporal trends in pelican foraging on the 25-km segment of the Yellowstone River, immediately downstream from Yellowstone Lake. During May-August, 1994 and 1995, 81% of the 1,581 pelicans counted during 62 searches were between the lake outlet and 6 km downstream. That river region may provide an efficient foraging site for pelicans because many Yellowstone Cutthroat Trout spawn there and the trout from the lake that spawn in river areas farther downstream pass through the region on both legs of their annual spawning migration. Most temporal variation (54-65%) in pelican abundance within years was explained by multiple linear regression models that had river discharge and the counts of trout or their redds (i.e., spawning “nests”) at one or the other of two major spawning areas as predictor variables. This study indicated that American White Pelican foraging on the Yellowstone River was associated, both spatially and temporally, with the spawning-related abundance of Yellowstone Cutthroat Trout in the Yellowstone River.

We investigated the distribution and behavior of 21 species of diving birds wintering in tidally active nearshore ocean off southern Vancouver Island, British Columbia, Canada. Using vessel surveys in one site and land-based observations at a second site, we found significant differences in the use of tidally affected water types among and within three foraging guilds (piscivores, plankton feeders and benthic invertebrate predators) and five families (Gaviidae, Podicipedidae, Phalacrocoracidae, Anatidae, Alcidae). The only abundant plankton feeder, Ancient Murrelets (Synthliboramphus antiquus), foraged more frequently than other birds in areas of deeper water (>10 m) with fast tidal flow and turbulence. Their abundance and diving activity were significantly higher at maximum tide flow than at slack tides. Piscivores used both slack water and moderate currents in a wide range of depths but, apart from alcids and Pelagic Cormorants (Phalacrocorax pelagicus), avoided areas of high current and turbulence. Pigeon Guillemots (Cepphus columba) had higher abundance at tide phases with maximum current, and within a channel with strong tidal flow they showed repetitive upstream flights interspersed with downstream diving bouts. Fish-eating mergansers and most diving ducks taking benthic invertebrates foraged in relatively shallow (<10 m) and slack water, and avoided turbulence. Six species representing all three guilds showed changes in the use of depth categories as tides changed between slack and maximum current, and four species changed their behavior in different depth categories. Although there was considerable overlap in foraging niches, the differences in distribution and behavior of guilds, families, and species of diving birds indicate a degree of resource partitioning within tidally-driven water categories during winter.

An aerial survey of post-breeding molting Harlequin Ducks (Histrionicus histrionicus) was carried out in late July 1999 along the southern half of the West Greenland coast. About 3,500 birds were located, which at this time of the year almost exclusively are males. Based on this observation a total of 5,000-10,000 Harlequin Duck males were estimated to molt in West Greenland. About 98% of the surveyed birds were found in the southern half of the study area. This distribution pattern may be linked to the presence of Atlantic Canadian males, which probably account for an appreciable proportion of the molting males in Greenland.

Until recently, very little was known about the basic ecology of the Harlequin Duck (Histrionicus histrionicus) in eastern North America, including molting locations. A combination of aerial, ground and boat surveys were initiated in 1989 (Québec) and 1994 (Newfoundland and Labrador), and continued through 1999, to locate their molting areas. Molting Harlequin Ducks were found in Labrador, Newfoundland and the Gaspé Peninsula and Anticosti Island, Québec. Coastal areas of southern Labrador, Grey Islands, northern Newfoundland, and Bonaventure and Anticosti Islands, southern Québec, were the most important sites. The tip of northern Labrador and possibly sites along the Québec North Shore and Greenland are the most likely sites where the rest of the eastern population molts. Molting chronology for the ducks in Québec is similar to those on the east and west coast of North America. Now that these sites are known, monitoring and, if necessary, protection of these sites can be considered.

In waterfowl, the male costs and female benefits hypothesis considers that the timing of pairing will depend on the balance between the costs and benefits for each sex. Females may benefit by increasing their access to food and social status, and by decreasing harassment from conspecifics, while maintaining a pair bond for a long period should be costly to males. To investigate costs and benefits of early pairing in the Harlequin Duck (Histrionicus histrionicus), we compared time budgets and frequency of interactions (agonistic, courtship, and mate guarding behavior) from paired and unpaired males and females. A total of 400 thirty-minute focal-animal sampling sessions were used for the analysis. Overall, feeding time did not differ between paired and unpaired birds of both sexes. However, regardless of their reproductive status, females spent about 15% more time feeding than males throughout the winter. While diving, paired males spent 4% less time underwater than unpaired males, but no difference was found between paired and unpaired females. Males spent more time on the surface between dives than females, yet the differences between paired and unpaired birds were not significant. Paired males were engaged in more interactions (mainly mate guarding) than unpaired males. Interactions received by paired and unpaired females did not differ overall, however, from late October to early May, interactions with paired females decreased, while interactions directed to unpaired females increased. Thus the pair bond, though being apparently costly to males, did not obviously benefit females by increasing feeding time. Early pairing in the Harlequin Duck may result from other factors, such as the advantages that pair reunion may confer.

Nearshore counts of birds on the water and time-lapse photography were used to monitor seasonal activity patterns and interannual variation in numbers of Horned Puffins (Fratercula corniculata) and Parakeet Auklets (Aethia psittacula) at the Semidi Islands, Alaska. The best period for over-water counts was mid egg-laying through hatching in auklets and late prelaying through early hatching in puffins. Daily counts (07.00 h-09.30 h) varied widely, with peak numbers and days with few or no birds present occurring throughout the census period. Variation among annual means in four years amounted to 26% and 72% of total count variation in puffins and auklets, respectively. Time-lapse photography of nesting habitat in early incubation revealed a morning (08.00 h-12.00 h) peak in the number of puffins loitering on study plots. Birds recorded in time-lapse images never comprised more than a third of the estimated breeding population on a plot. Components of variance in the time-lapse study were 29% within hours, 9% among hours (08.00 h-12.00 h), and 62% among days (8-29 June). Variability of over-water and land-based counts is reduced by standardizing the time of day when counts are made, but weather conditions had little influence on either type of count. High interannual variation of population indices implies low power to detect numerical trends in crevice-nesting auklets and puffins.

Chilean Flamingo (Phoenicopterus chilensis), Andean Flamingo (Phoenicoparrus andinus) and James’ Flamingo (Phoenicoparrus jamesi) occur in the high Andes water bodies of Argentina, Bolivia, Chile and Perú. The objectives of this study were to analyze seasonal variations in flamingo abundance and movements related to climatic conditions, and to identify the physical characteristics of water bodies determining the seasonal distribution and abundance. Flamingo numbers reached a peak in summer and diminished in winter. Within the high Andes region, the Andean Flamingo was mainly found in the Dry and Dry-cold climatic sub-regions during summer. This species moved into the Dry sub-region in winter. In summer, James’ Flamingo primarily occurred in water bodies of the Dry-cold sub-region. During winter, some individuals remained in the Dry-cold sub-region, and others moved to the Wet, Dry and Desert sub-regions. In summer, Chilean Flamingo occurred principally in the Dry sub-region. In winter, few remained in the Dry sub-region, and most birds moved to the Wet sub-region. These seasonal changes in flamingo numbers within the high Andes show that in winter, these birds move from sub-regions with extreme climatic conditions (Desert and Dry-cold sub-regions) to those with more suitable conditions (Wet and Dry sub-regions). The seasonal fluctuation in abundance might be explained by intra- and inter-regional movements in response to adverse climatic conditions. The relationships between water body physical characteristics and flamingo species show that the Chilean Flamingo mainly used lakes, both in summer and winter. James’ Flamingo usually used saline playa-lakes at high altitudes in summer and winter. Andean Flamingo selected salt-flats during summer and lakes in winter. It is suggested that Chilean and James’ Flamingos are habitat-specialists and the Andean Flamingo is a habitat-generalist.

The diet of the Sanderling (Calidris alba) was studied using 105 droppings, 34 pellets and direct observations of feeding behavior. This study was carried out during the non-reproductive seasons of 1996 to 2000 in Monte Hermoso, SW of Buenos Aires, Argentina. A total of eleven prey items were identified, with beetles (Coleoptera), Mussels (Brachydontes rodriguezi), clams (Corbula sp.), amphipods (Corophium sp.) and Diptera being the most frequent. The consumption of polychaetes, algae, ants and small fish was also recorded. Sanderlings followed foraging American Oystercatchers (Haematopus palliatus) and cleaned out the valves of mussels and clams (Mesodesma mactroides) left by them. Mussels and beetles were the most constant and dominant prey during the study period. The association of Sanderlings with sandy coasts with rocky patches or restingas is probably due to the rich and diverse invertebrate communities present in this kind of environment, which allow birds to change feeding techniques between different substrates.

During 20 years, numbers of Greater White-fronted Geese (Anser albifrons) wintering in Japan have increased 5.6 times (ca. 46,000 in 1999), with over 80% of the geese concentrated around Lake Izunuma-Uchinuma, in northern Japan. Detailed information on the wintering ecology of the geese had not been investigated in Japan and the daily activity pattern and habitat use of the geese were studied around the lake in three winters (October-February), 1996/97, 1997/98 and 1998/99. The daily activity pattern, i.e., flight timing and behavior relating to environmental factors (light intensity, snowfall, temperature and wind speed), was similar to that for several other geese species in temperate areas. The geese wintering in Japan depended exclusively on rice in fields; they foraged in stubble fields, where the density of rice grains was much higher than that in plowed fields. However, the area of stubble fields around the lake has decreased from 1980 to 2000, while combine harvesters replaced machinery, which only cut the rice plants (reapers). The amount of rice grains left in the fields by the combine harvesters was 8.7 times than the reapers. The replaced cropping machinery increased the abundance of food and might facilitate an increase in geese numbers.

The Common Tern (Sterna hirundo) breeds in North America and migrates to South America at the end of the northern summer. At Punta Rasa (Buenos Aires Province, Argentina) this species is present from November to April. Between December 1995 and March 1996, the peak numbers of 20,000 individuals were recorded in March. These numbers place Punta Rasa as one of the most important wintering sites in South America. The daily pattern of abundance was similar throughout the austral summer with a peak at dusk. Although tidal height did not alter this pattern, it determined the availability of roost sites, constraining the spatial distribution of terns.

Colony attendance by the Atlantic Puffin (Fratercula arctica) was examined to investigate daily and seasonal patterns of variation, and to determine the biological or environmental factors, if any, which serve as useful predictors of such variation. Observations were made during the pre-laying and incubation stages of the breeding season on a study plot at a colony on Gull Island, Witless Bay Seabird Ecological Reserve, Newfoundland, Canada. The number of birds on the surface of the colony increased through the day, but the peak number differed between consecutive days. Colony attendance showed a possible cyclical trend across days with a periodicity ranging from two to six days. Residency time of individual birds was associated with the extent of colony attendance, suggesting a positive feedback loop between individual short-term turnover and numbers present on the breeding slope. Neither weather nor presence of large gulls was related to puffin attendance. The correlation between residency time and colony attendance suggests that puffins may be more confident on land when surrounded by other conspecifics. With the high variability and no obvious factors that influence attendance, the use of colony surface counts of individuals to infer population parameters is likely limited in this species.

We report for the first breeding attempt of the Lesser Black-backed Gull (Larus fuscus) in the Macaronesic Archipelago, in Alegranza Island (north of Lanzarote, Canary Islands). A nest with three eggs was found on June 2001, and at least one fledgling was seen in August with two adults. Additional observations suggest that 5-6 pairs may breed on Alegranza Island and nearby Montaña Clara Island. This is the southernmost breeding record for the species, increasing its known breeding range by 2,000 km.