Agonistic interactions between Great Cormorants (Phalacrocorax carbo) in a roost have been studied to detect possible social dominance causing spatial segregation in relation to age. Adults tended to dominate first- and second-winter birds, and were found relatively higher in the roost, where they are probably the safer from human intruders. Because of the high proportion of adults, attacks frequently involved two adults. No differences were found between the frequency and success of attacks in relation to the age of the birds arriving to the roost, perhaps indicating that pre-attack display represented an efficient form of agonistic communication. The number of attacks was not correlated with the number of cormorants in the roost, probably due to a constant density of birds, unaffected by the size of the roost.

The diving patterns of the Antarctic Shag (Phalacrocorax bransfieldensis) were studied by direct observation on individuals foraging at Harmony Cove, Nelson Island, South Shetland Islands, during the 1995/96 and 1996/97 breeding seasons. The individuals observed foraged in shallow waters, mainly solitarily and presumably dived aerobically. The shags displayed relatively short diving bouts composed of few dives. During the 1995/96 breeding season, the duration of the dives decreased with the increase in the number of dives per bout and increased with the diving depth. These relationships were not statistically significant in 1996/97. In both seasons, the duration of the dives was positively related with both the surface resting time preceding and succeeding the dive, which may indicate that these birds display anticipatory or reactive dives probably according to the foraging conditions. Shags at the surface were seen swallowing fish longer than 15 cm; smaller fish as well as invertebrates may have been ingested underwater. The mean diving efficiencies of the bouts fall within the range reported for phalacrocoracids, but values of diving efficiency below unity were observed.

During 1980-2002, the distribution of nesting and brood-rearing Snow Geese of the subspecies (Chen caerulescens caerulescens) in the Sagavanirktok River delta study area, Alaska, were documented during monitoring programs for the Endicott oilfield. Densities for Snow Goose nests on Howe Island were estimated based on mid- to late-June aerial photographic surveys. Brood-rearing flocks and total geese were based on late-July to early-August aerial survey or banding locations. The highest nesting density was mid-island; Snow Geese shifted their nesting distribution away from a den site when Arctic Foxes (Alopex lagopus) were present on the island. Most Snow Geese that rear broods in the Sagavanirktok River delta study area nested on Howe Island. Brood-rearing Snow Geese expanded their dispersal range with increasing numbers of total adult geese. The movement of brood-rearing Snow Geese to coastal salt marsh sites up to 35 km from Howe Island and movements into non-saline habitats along the west channel of the Sagavanirktok River suggest that the salt marsh resources in the Sagavanirktok River delta may not be able to support more than 500 Snow Geese.

The breeding biology of the Magellanic Penguin (Spheniscus magellanicus), including the timing of laying, brooding and fledging, foraging trip lengths during incubation and brooding and diet in relation to breeding success, was investigated at Volunteer Beach in the north east of the Falkland Islands during the 2001/02 breeding season. Egg-laying dates were between 12 October and 1 November, with an overall hatching success of 65%. The length of foraging trips during incubation ranged from 2-15 days. Chicks were provisioned daily during the 23 day brood period, and then at a mean interval of two days during the unattended period, until fledging occurred in late January and early February. Successful pairs laid significantly earlier and undertook shorter foraging trips during incubation and brooding compared to unsuccessful pairs. The mean breeding success of 0.2 chicks/pair was low compared to the ten year mean at the study site and was possibly due to a lower abundance of squid, which is the preferred food for Magellanic penguin chicks in the Falkland Islands. The results obtained are discussed with regard to the breeding biology of the Magellanic Penguin on the mainland of South America. However, further research in subsequent seasons is required to determine whether the observed differences in breeding biology compared to elsewhere in the species range is typical behavior or the result of the changed prey availability.

The Red Phalarope (Phalaropus fulicarius) is a rare species in west Greenland, where it generally breeds on islands in association with the Arctic Tern (Sterna paradisaea). The strength of this association was confirmed on the archipelago of Grønne Ejland, the largest tern colony in Greenland, where Arctic Terns inhabited all four major islands until 15 years ago, but now have abandoned two of them; the Red Phalarope left the same two islands after a few years, but not the islands still inhabited by terns. The terns apparently disappeared from the two islands due to the presence of Arctic Foxes (Alopex lagopus) over several years. The disappearance of the Red Phalarope could have been a response to the absence of breeding terns, or could have happened as a direct result of predation and disturbance from foxes. The Red-necked Phalarope (P. lobatus), however, still breeds on the islands abandoned by the terns. It might be that the Red Phalarope is more vulnerable to fox predation than the Red-necked Phalarope, which may partly explain why the former of the two species in west Greenland breeds only in tern colonies on islands, whereas the latter is widely distributed, including inland areas.

We analyzed data on numbers and annual trends of breeding terns and gulls based on censuses of all colonies of the Caspian Tern (Sterna caspia), Forster’s Tern (S. forsteri) and California Gull (Larus californicus) in the San Francisco Bay estuary from 1982 to 2003. All species used nesting substrates that were flat, largely non-vegetated, had a wide view in all directions, and were composed of sand, gravel, or earth. The estuary supported 17, 13, and seven colonies of each species, respectively. Nesting terns were primarily on salt evaporation pond islands and tidal islands. The largest colony of California Gulls was on a deactivated salt pond. Total numbers of each species in 2003 were about 2,300, 2,450 and 21,200 breeding birds, respectively. Numbers of Forster’s Terns declined significantly during the study, while California Gulls increased, and the number of Caspian Terns was stable. Numbers of each species at each colony site have shown considerable annual variation. We attribute the lack of colony site fidelity of each species, and the decline among Forster’s Terns, primarily to mammalian predation, human disturbance, and possibly annual variation in food availability. Flat, minimally vegetated islands, which are few in the estuary, are critical for maintaining nesting terns and California Gulls. Yet, the planned restoration of 65% (9,050 ha) of the salt pond complex of the San Francisco Bay estuary will likely remove some of the salt pond islands and levees where 20% of the Caspian Terns (438 birds), 80% of Forster’s Terns (1,958) and 96% of California Gulls (20,210) were nesting in 2003. We recommend that restoration plans should include the creation of sizeable tracts of islands specifically designed to provide nesting habitat for these larids. These replacement sites should be in place soon after the restoration has been implemented; i.e., well before scheduled completion. This is especially important because severe habitat limitation would lead to competition for nesting space among the three species, a situation expected to result in exclusion of the terns by the gull, which nests earlier, are larger, more abundant, and more aggressive.

We compared the reproductive performance of the Common Tern (Sterna hirundo) from 1991-2002 at four restored colonies in Maine that differ in location (inshore, nearshore and offshore sites), colony age and size and predation. Specifically, phenology, clutch size, survival, growth, provisioning rates and predation intensity and frequency were compared between sites. Common Terns nesting on the two inshore islands laid larger clutches, hatched chicks earlier that grew faster, reached a greater asymptotic mass, and had a greater chance of fledging than conspecifics on a nearshore and an offshore colony, despite greater predation pressure. Individuals nesting at the offshore site suffered reduced reproductive performance, which may be due to colony location with respect to foraging areas. Clutch size, chick provisioning rates and first hatch dates (earlier) declined as colony size increased. Although inshore nesting terns produced more chicks on average, extensive predation in some years caused high breeding failure, resulting in a “boom or bust” productivity situation for these islands. Differences in predation and performance between inshore, nearshore and offshore islands have important implications for the restoration, conservation and management of terns in this region. Nearshore sites offer the best restoration potential and should be strongly considered when available.

Aspects of the biology of the Little Tern (Sterna albifrons) were studied at the Ebro Delta (northwestern Mediterranean) during 1996-1997, including colony site selection, clutch size and egg size. Using a single visit to avoid disturbances, average number of eggs was 2.62 eggs per nest, and was significantly larger in 1996 than in 1997, when the modal clutch size was only two eggs. Mean egg volume was 8.88 cm³ (SD ± 0.57), and mean egg size in a clutch (for both two- and three-egg clutches) was also significantly larger in 1996 than in 1997. Furthermore, average egg volume in three-egg clutches (clutches that were probably completed) was significantly different among the four main breeding areas within the delta. Clutch size was not significantly different among breeding areas in either year. Little Terns bred associated with other colonial Charadriiforms more than in other Mediterranean breeding areas. The terns associated with all the commonest colonial species of shorebirds, but never associated with the Yellow-legged Gull (Larus michahellis), Audouin’s Gull (L. audouinii) or Black-headed Gull (L. ridibundus). The number of breeding pairs decreased from 625 in 1961 to 332 in 2003, this decline occurring mainly since the early 1990s. Mean population declined significantly by 2% per year for the whole period. During the last decade, the number of breeding areas has increased from four to nine, despite the decrease in breeding numbers (rate of decrease 7.1% per year). Nothing is known about the factors driving this decrease, but changes are probably linked to processes in other colonies at a metapopulation level.

The establishment of regular wintering of the White Stork (Ciconia ciconia) in southern France has been documented by regular census data and individual identification of banded birds. The number of wintering storks rose from eight in 1996-1997 to 172 in 2003-2004. Most records (87%) came from the Montpellier region (43°34’N, 3°54’E). The birds mainly originated from western Germany, eastern France and western Switzerland and about half were probably immature. Compared to storks observed on autumn and spring migration, first-winter birds were under-represented. We discuss the factors likely to explain the settlement of this new wintering area: its location on the migration route of the increasing northwest European stork population, the presence of a rubbish dump and adverse effects of wintering in Africa.

The effects of the environmental and species’ characteristics were analyzed for the richness and distribution of the dabbling and diving waterbirds in a wetland complex with 26 ponds (0.1-88.6 ha) in southeast Spain. These environments are being lost on a global scale through human activity. Morphological, geographical, hydrochemical, vegetative and temporal parameters of the ponds (11 in total), as well as characteristics of the species, were sampled to identify those variables with the capacity to predict the effects provoked by the habitat configuration. The function of the size and the isolation, as variables related to the habitat patchiness, as well as the development of the emergent vegetation of the wetlands were discriminated as forecasters of number of species. The avian abundance had an important role in the capacity of the birds to occupy ponds (sampling hypothesis). The differences in the abundance of species probably favored their orderly loss from the wetland complex at the same rate as the ponds diminished in size (“nested” pattern). The results obtained imply the need for the conservation or restoration of numbers of wetlands, paying special attention to the largest, with peripheral vegetation cover around large, open water bodies in complexes with more than one pond, to preserve the greatest number of species against the loss of wetlands which is occurring worldwide and is a cause of biodiversity decline.

The Great Blue Heron (Ardea herodias) and Great Egret (Ardea alba) nested in eight colonies along the Upper Mississippi River, USA, and individual birds were followed by airplane to feeding sites during the nesting seasons in 1995-1998. Both species used braided channel/backwater habitats for feeding more than expected, based on availability, and open pool and main navigation channel less than expected. Most individuals of both species fed <5 km from their breeding colony and avoided sites >10 km away. Habitat and distance need to be considered simultaneously when assessing habitat quality for herons and egrets. The Great Blue Heron flew farther to feeding sites during the care-of-young period than during incubation and the Great Egret showed the opposite pattern. The Great Blue Heron tended to feed solitarily; only 10% of the feeding flights ended at a location where another heron was already present. About one-third of Great Egret feeding flights ended at a location with another egret already present. Colony placement on the landscape seemed to be a function of the feeding radius of each colony.

Commercial harvests of the Common Eider (Somateria mollissima) and King Eider (S. spectabilis) was studied at the local market in Nuuk (southwest Greenland) during the hunting season (Oct.-May) in 2000 and 2001. The goal was to quantify composition (species, sex and age), sources (hunting or bycatch), and spatio-temporal distribution of the harvest. Hunting within 30 km of the city was the source of 98% of all eiders sent to market from October until March. In contrast, bycatch in gillnets accounted for 52% of the eiders brought to the market in March and April. In April, most bycatch were from remote fjord habitats, which seem to hold a high proportion of adult Common Eiders. As measured by the removal of potential reproductive eiders, the spring harvest (April and May) was critical for the Common Eider, while the impact of harvest was highest during midwinter (January and February) for the King Eider. Sympatric distributions within hunting areas complicate management of both species. Spring hunting and gillnet bycatch are of high management concern.

When studying breeding dispersal with marked individuals, manipulation-induced disturbance should not affect movement patterns. As part of a study on the Little Egret (Egretta garzetta), we tested whether the capture of breeding adults at their nest and handling (i.e., disturbance) increased their probability to move to a new colony in the subsequent breeding season (i.e., breeding dispersal). The proportion of adults disturbed in a given year that had changed colony in the subsequent breeding season was compared with the dispersal of adults observed during at least two consecutive years at colonies and not disturbed on the previous year: (1) birds marked as chicks and (2) birds marked as adults and observed ≥ two years after capture at the nest. Disturbed birds were not found to have an increased propensity to disperse. We conclude that, for this species, capture did not increase the subsequent breeding dispersal.

We studied the predation of the Western Gull (Larus occidentalis) on the Eared Grebe (Podiceps nigricollis) from December 2002 to June 2003 at a solar saltworks. Mechanisms of predatory behavior, such as use of perching site, attack maneuvers and killing and catching grebes, as well as behavior of the grebes as a response to the presence and attacks by gulls, were recorded. In all 35 cases where a gull attempt to feed was seen, it was successful in every case. This is the first report about predation by the Western Gull on the Eared Grebe.

The Ivory Gull (Pagophila eburnea) has a circumpolar breeding distribution and spends the entire year at high latitudes in the Arctic and North Atlantic oceans. Due to its remote breeding locations and nomadic wintering habits, little detailed information on the ecology of this species exists, and no estimates of survival rate are available. Recent surveys have shown a dramatic decline, with an estimated 250-350 pairs now breeding in Canada. Across its range, the Ivory Gull was traditionally harvested by northern communities, and, although now protected, it is still shot in some regions. Ivory Gulls were banded in the Canadian Arctic (N = 1,526) in the 1970s and early 1980s. Most recoveries (N = 17) came from birds shot in northwest Greenland, while five birds were shot in Canada. As yet, no birds banded at more southerly locations have been recovered. Annual adult survival rate of 0.86 ± 0.04 and reporting rate of 0.03 ± 0.009 were calculated for birds banded at Grise Fjord and Seymour Island. The higher recovery rates of Ivory Gulls banded in northern areas suggests that hunting could have an impact on their already small population. Education programs to prevent further hunting of the species are recommended.

This paper describes the diet of the Red Knot (Calidris canutus) at Punta Rasa; the southern extreme of the Ramsar Site at Bahía Samborombón, in the Buenos Aires province, Argentina. Data presented here are mostly based on fecal analysis. We also used gizzard content analyses of four casualties that occurred during the catching operations. Remains of prey occurred in all droppings and consisted entirely of shell fragments of the Mud Snail (Littoridina australis, Hydrobiidae: Mesogasteropoda). A total of 295 droppings were analyzed containing Mud Snail fragments from which the size distribution of ingested L. australis could be estimated using a regression equation derived from a reference collection. In both study years (1995 and 2000), the size distribution of ingested Mud Snails differed significantly from size distribution present in the habitat; however, average length of ingested Mud Snails was similar in both periods. Three of the four gizzards analyzed contained Mud Snails. The fourth contained a common Scarabaeidae beetle (Dyscinetus sp., Coleoptera) present in the area in autumn. Results support the hypothesis that the Red Knot has a specialized diet and select medium-large size food items.