Systematic observations of staging dabbling ducks through 24 autumns (1978 to 2001) in a Danish wetland show that the numbers of the numerous species Eurasian Wigeon (Anas penelope), Eurasian Teal (Anas crecca) and Mallard (Anas platyrhynchos) were positively and only correlated and with the water level. For the less numerous species, Northern Shoveler (Anas clypeata) and Northern Pintail (Anas acuta), the correlation with the water level was less evident, and an effect of the overall size of the flyway population was demonstrated. The increasing numbers recorded with rising water level may have two explanations or probably a combination. One is redistribution of birds migrating through the region, reflecting that the available habitat limits the numbers of ducks recorded, and the other is prolonged stay for individual birds when conditions are favorable. The relationship between average seasonal water level and average number of ducks were modelled to estimate a minimum favorable water level to be maintained throughout the autumn, a tool proposed for optimizing the site for staging dabbling ducks.

In North America, the Double-crested Cormorant (Phalacrocorax auritus) is currently abundant, widely distributed across five broad geographic regions, and often perceived as overabundant. In many U.S. states and Canadian provinces, policy makers are pressured to significantly reduce cormorant numbers, primarily to minimize conflicts between cormorants and fish resources. Concurrently, large-scale conservation plans recently developed for birds in the Americas depart from the traditional narrow focus on threatened and endangered species to encompass broader and more representative goals (e.g., Partners in Flight’s objective to “keep common birds common”). In recent waterbird conservation initiatives, historic distribution and abundance provide the basis for conservation focus; these initiatives advocate conservation of birds in natural numbers and natural habitats. To provide a context in which current populations of Double-crested Cormorants can be understood, we reviewed historic and current breeding and wintering records to determine historic distribution (pre-1900), current distribution (1970-1999), and extent of range expansion across North America. Early records suggest Double-crested Cormorants were present in large numbers throughout much of their current range; colonies and flocks much larger than any known in the 1990s are well documented. However, numbers sharply declined through the late 1800s as cormorants were greatly reduced and/or extirpated in many areas. The population partially recovered through at least the mid-1900s, but experienced a second major decline during the 1950s-1970s. In the late 1970s, a second rebound began across much of the continent; the largest breeding populations (Canadian/U.S. interior, Atlantic Coast >80% of total) increased from approximately 32,000 pairs in the early 1970s to >226,000 pairs in the late 1990s. Comparison of historic and current records challenges the opinion that cormorants are currently overabundant, and suggests that perception of overabundance rests on socio-political rather than biological or ecological factors. For this species, and others that are seen as competitors with humans, limits of human tolerance (i.e. “social carrying capacity”) are far narrower than those of biological carrying capacity. Because large numbers have been typical for cormorants historically, population targets based on fishery or other objectives derived from human values will likely be readily surpassed, require intensive management, and significantly depart from the concept of conserving birds in natural numbers and natural habitats. Although managing fish-eating birds to benefit fishery yields may increase some fish populations, this approach does not resolve or address the underlying problems causing current fish population declines across the continent, and is in direct conflict with current broad scale conservation initiatives. To ensure inclusion of cormorants and other fish-eating birds in these conservation plans, the avian conservation community must continue to press for programs based on ecosystem health and process that recognize humans, fish and cormorants as three components of a complex system driven by many species and dynamic interactions.

Once an abundant and conspicuous presence in wetlands across much of north-central North America, Trumpeter Swan (Cygnus buccinator) poplulations were decimated in the mid- to late 1800s by a combination of market hunting, subsistence hunting, and habitat loss. Since then, restoration has focused primarily on reintroduction efforts in which captive-reared birds are released and then monitored. From 1991 to 1993, 44 birds were released into Seney National Wildlife Refuge (Schoolcraft County, Michigan) in a multi-agency attempt to enhance the breeding population of this species in the Upper Great Lakes region. To provide information useful to swan restoration efforts elsewhere, this paper summarizes 14 years of Trumpeter Swan occupancy and productivity at Seney. In doing so, we document the first substantial inter-annual decline in swans on the Refuge and provide evidence that suggests birds may now be dispersing onto other lakes and wetlands in the eastern Upper Peninsula of Michigan. We also present information from which we infer processes regulating swan numbers and rates of productivity and discuss both the continued need for monitoring and the need for research to examine the effects swans might have on other components of aquatic ecosystems at the Refuge.

We monitored the movement, distribution and site affinities of radio-marked Tule Greater White-fronted Geese (Anser albifrons elgasi) during spring and summer in Alaska, 1994-1997 and 2004. Our assessment of summer movements was comprehensive, as locations were obtained during prenesting, nesting, and molt for over 90% of geese with active radios captured during winter or the previous summer in Alaska. Geese arrived to coastal and interior marshes in the Cook Inlet Basin (CIB) from mid April to early May, after which they moved to nesting areas in the upper CIB. Nesting birds used coastal staging areas in close proximity to eventual nest site location. Molting sites included a sub-glacial lake system in the upper CIB, although up to 50% of geese underwent a molt migration to wetlands across the Alaska Range, 400-600 km west of the CIB. Geese that molted at distant sites returned to the CIB before autumn migration. Length of stay in the CIB varied among years from 108-119 days, and averaged 116 days. Summer home-range sizes, exclusive of molting areas, averaged >273,000 ha, and were substantially larger than reported for other northern-nesting waterfowl. No radio-marked geese were found nesting in the vicinity of Redoubt Bay on the west side of Cook Inlet, and few nested near the Susitna Flats, the only other previously known nesting areas. The absence of nesting geese from Redoubt Bay corroborates aerial survey data showing a precipitous decline in the use of the west side of Cook Inlet between the early 1980s and early 1990s. The change in distribution of geese is likely related to a major eruption of Redoubt Volcano in 1989 that significantly altered landscapes used by nesting, brood rearing, and molting geese in the vicinity of Redoubt Bay. High inter-site movements of Greater White-fronted Geese throughout summer in south central Alaska likely increases exposure to predation, but also promotes social interactions and facilitates pioneering of distant, and diverse habitats in a vast, patchy, and often unpredictable landscape.

The island of Selvagem Grande holds one of the most important colonies of Cory’s Shearwater (Calonectris diomedea) in the Atlantic. Historical records suggest a stable population well in excess of 100,000 pairs. A succession of massacres in 1975 and 1976 dramatically reduced this population to less than 10% of the original numbers. Since 1977 strict protection was enforced and the population started a steady recovery. However, between 1995 and 1998 an alarming decline, of more than 13% of the birds, was reported and concurrently the monitoring work was interrupted. Data from other colonies in the Atlantic and the Mediterranean also indicated significant regional declines, some of which appear to be driven by unsustainable levels of accidental mortality in fishing gear. In order to investigate the persistence of the regressive trend at Selvagem Grande, we carried out a global census of the colony in June 2005. We counted 20,555 occupied nests and estimated the total breeding population at 29,540 pairs. The population still appears to be recovering from the massacres of 1975-1976, at an average rate of about 4.6% per year over the past 25 years. Our data reveal that Selvagem Grande now harbors the largest known Cory’s Shearwater colony in the World. Results from this study suggest that this population is not, as yet, suffering from unsustainable fisheries-related mortality, which would be reflected in a decline in numbers. This situation contrasts with that of the Mediterranean, where significant mortality in fishing gear has been linked to shearwater population declines.

This study reports on the number of nests and colonies of Great Egret (Ardea alba), Little Egret (Egretta garzetta), Cattle Egret (Bubulcus ibis), Chinese Pond Heron (Ardeola bacchus) and Black-crowned Night Heron (Nycticorax nycticorax) in Hong Kong between 1989 and 2004. Little Egret, Chinese Pond Heron and Black-crowned Night Heron were the dominant local breeding ardeids. Regression analysis of the number of nests and colonies with year revealed that the number of nests of Great Egret, and the number of colonies of all ardeids, except the Black-crowned Night Heron, showed a significant increase. The number of nests of Great Egret increased from no nests in 1989 to 85 in 2004. The other species fluctuated from 100 to 300 nests each, except for Cattle Egret which stayed steady at about 100 nests. Regression analysis of the relationship between climate variables and residuals, after removing the effect of any long-term trend, shows that there was a significant positive association of the number of nests of Cattle Egret with total rainfall during breeding. The increase in numbers of colonies, but not the number of nests, indicated that previously large colonies had split into smaller ones, presumably due to loss of feeding and nesting habitats. The El Niño events in 1991 and 1997, but not in 1994, coincided with declines in nests. The magnitude of El Niño may be related to the impact on nesting ardeids, but other local confounding variables, in particular feeding habitat availability, should also be considered. The number of Great Egret nests in Hong Kong is of regional importance, as it is about half the known nests in southern China. It is recommended that monitoring of breeding success should be initiated in major colonies, as well as an integrated wetland monitoring for Deep Bay and Starling Inlet.

A survey of ardeid nesting colonies in Hainan Province, China, was made between May and August 2004 and recorded 5,287 nests of four species (Little Egret Egretta garzetta, Cattle Egret Bubulcus ibis, Chinese Pond Heron Ardeola bacchus and Black-crowned Night Heron Nycticorax nycticorax), in 18 colonies in the northern area. Chinese Pond Heron was the dominant nesting species (62% of the total nests), while the Black-crowned Night Heron was the least abundant (4%). Numbers of the Chinese Pond Heron in Hainan is probably related to the presence of extensive ricefields in this area. Fewer numbers of nests of all species in the field were recorded compared with expected obtained from nest densities over a ricefield-dominated landscape in a previous study of ardeid nest abundance in central China. This suggests that nest density in central China could not be applied in Hainan and the assumption of 5 million nests in China requires further study. Based on available information for south China, numbers of nesting Cattle Egret and Chinese Pond Heron in Hainan (75% of total nests of each species), Black-crowned Night Heron in Guangdong and Guangxi, and Great Egret in Hong Kong (80%) are of regional importance. Using media to invite readers to report nesting colonies is recommended for similar surveys in a large area as it provides a cost effective approach to minimize sampling effort.

The International Waterbird Census (IWC) is one of the longest-running bird monitoring schemes in the Western Palearctic. Most of its data are collected with land-based counts, the reliability of which is largely unknown. This study compared estimates of land-based vs. aerial counts, and the relative conservation values of coastal sites obtained with the two methods. The data were collected in the West-Estonian archipelago of the Baltic Sea in 1993, and analyzed at two spatial scales (mean area of plots 9 and 36 km²). Among nine waterfowl species, land-based and aerial census provided closely correlated local population estimates for the Mute Swan (Cygnus olor), Steller’s Eider (Polysticta stelleri), Long-tailed Duck (Clangula hyemalis) and, at the larger scale, for the Mallard (Anas platyrhynchos). However, small numbers of all species, except the swan, remained undetected with the land-based census, and numbers of Mallard and Steller’s Eider were also systematically underestimated. The areas having the highest conservation value were reliably identified with the land-based census, particularly at the larger scale. Hence, land-based studies are in general accordance with the aims of the IWC, but the absolute population estimates should be interpreted with care.

Two different types of food samples from the Black Skimmer (Rynchops niger) were collected during the non-breeding season: spontaneous regurgitations and pellets. These two samples were analyzed and differed in the number of taxonomic categories represented, the number of fish prey species found and in the estimated size of fish prey. However, key prey were the same and well represented in both types of samples, suggesting that both sources gave accurate information, at least for the main items. Given that collecting pellets involves little effort and low disturbance to the birds, the value of the analysis of pellets to monitor long-term dietary changes in the Black Skimmer and other seabird species of similar size and diet is considerable. Correction factors are proposed to overcome underestimation of the total length and mass of some fish prey species remains found in pellets.

The role of food abundance and vegetation structure in selection of foraging habitat by the Snail Kite (Rostrhamus sociabilis) was explored. Selection of available foraging patches of either dense or sparse habitat structure within two prairie habitat types used extensively by foraging kites, Eleocharis flats and Panicum flats were examined. Estimated Apple Snail (Pomacea paludosa) densities on our study site ranged from 0.33 to 1.58 per m². Vegetation structure (sparse vs. dense) of the habitat type had a greater influence on where prey was captured than did site, the dominant emergent vegetation, or prey abundance. These results are consistent with previous suggestions that dense vegetation may obscure prey and limit or preclude use of densely vegetated habitats by foraging kites. This may be true, even when prey is in relatively high abundance, and may indicate the difference between prey abundance and availability. Most water management recommendations related to the Snail Kite call for prolonged inundation, based on an explicit assumption that this results in increased Apple Snail abundance. Even when directed at a single species such as the Snail Kite, water management may need to be considered in a more holistic framework that considers factors that influence the resulting vegetation communities, rather than just production of Apple Snails.

Similar to other bird species, Coots (Fulica atra) usually interrupt feeding to look up and to scan their environment for predators. Predation risk may differ among feeding methods. Coots may suffer from aerial predators both in the water and on land, and additionally from terrestrial predators when feeding on land. Samples were obtained from 10 different study sites where Coots fed both on water and on land (N = 139 feeding-bouts). Flock structure differed significantly between feeding methods, and nearest-neighbor distance was lower on land (water: 5.2 ± 0.3 Coot length, land: 2.8 ± 0.2 Coot length). Mean feeding-bout length--defined as the time of uninterrupted feeding--was significantly different (water: 12.2 ± 0.8 s, land: 9.4 ± 0.8 s). When using the study sites as samples, aquatic feeding-bouts were also significantly longer. In a general linear mixed model a significant influence of feeding method on feeding-bout length was found, again with a higher bout length in the water. Feeding-bout lengths were positively correlated between aquatic and terrestrial feeding within the same study site. These results suggest that Coots perceived more safety during aquatic feeding which was reflected in longer feeding-bouts.

Survival of Semipalmated Plover (Charadrius semipalmatus) nests was compared in areas with and without nesting Arctic Terns (Sterna paradisaea) to determine whether the protection provided to plovers by association with this colonial species is passive or aggressive. Artificial and natural nests placed ≤100 m from terns had similar rates of survival (<10% of all nests lost to predators), and benefited substantially from protection against predators through aggressive behavior of nesting terns. Natural nests had much higher survival than artificial nests when positioned >100 m from nesting terns, suggesting that the presence of incubating adult plovers reduces the probability of nest predation. Nesting in association with Arctic Terns may represent an alternate form of habitat selection by Semipalmated Plovers and suggests that plovers can employ alternate nest defense strategies when opportunities are present.

Great Crested Grebes (Podiceps cristatus) wintering on prealpine lakes of north Italy are considered to cause economic damage to fish, reducing the stock of native Bleak (Alburnus alburnus). We experimentally investigated the effectiveness of three deterring actions (gas-cannon, crackers and shooting) in four study sites at Lake Como, by comparing the time-budget and space-use of wintering grebes in absence and presence of disturbance. All dissuasion methods affected grebe behavior and position on the lake, but some resulted more effective than others. The gas-cannon detonations had little effect, but, crackers and shooting caused significant changes in grebe behavior. Grebes spent less time feeding, resting and preening, but more time moving/swimming during dissuasion than in the control situation. Moreover, birds also moved away from the areas with bleak shoals, resulting in a significant decrease in grebe numbers with either dissuasion methods. Although dissuasion reduced feeding of grebes in areas with shoals of Bleak (Alburnus alburnus), and probably reduced grebe predation on immature fish at localized areas, it involves intensive effort, in terms of man-days.

We compared time-budgets and return rates of breeding female Barrow’s Goldeneyes (Bucephala islandica) fitted, or not, with transmitters attached with backpack harnesses in 2001-2004 in southern Québec. We compared the mean proportion of time devoted to feeding, locomotion, alert, resting, preening, and maintenance (i.e., resting plus preening) by females observed ≥200 min. Females with backpacks (N = 5) spent significantly less time feeding (x ± SE: 25 ± 5% versus 43 ± 3%) and more time in maintenance activities (51 ± 6% versus 31 ± 4%) than females without transmitters (N = 6). Mean time devoted to other behavior did not differ significantly. Upon release, females appeared disturbed with the backpack, actively bathing, preening and/or flapping wings. Of the females with transmitters observed ≥200 min, three spent 4%, 8%, and 57% of their preening time at their transmitter, antennae or harness. None of the 16 females harnessed in 2001-2003 were recaptured in nest boxes or seen again on the study area in 2002-2004. For comparison, 66% of adult female Barrow’s Goldeneyes captured in nest boxes and marked with leg bands in 2000-2002 were recaptured or seen again in subsequent years. We do not recommend the use of harnesses on diving ducks and sea ducks as it may affect their behavior and survival, at least for birds wintering in areas where conditions are severe.