Changing numbers of three gull species in the British Isles

Between-population variation of changes in numbers can provide insights into factors influencing variation in demography and how population size or density is regulated. Here, we describe spatio-temporal patterns of population change of Herring Gull (Larus argentatus), Lesser Black-backed Gull (L. fuscus) and Great Black-backed Gull (L. marinus) in the British Isles from national censuses and survey data. The aim of this study was to test for density-dependence and spatial variation in population trends as two possible, but not mutually exclusive, explanations of population changes with important implications for the understanding of these changes. Between 1969 and 2013 the three species showed different population trends with Herring Gulls showing a strong decline, Great Black-backed Gulls a less pronounced decline and Lesser Black-backed Gulls an increase until 2000 but then a decline since. Population changes also varied between different regions of the British Isles, with the Atlantic coast showing declines and the North Sea coast increases in all three species. Population changes were density-dependent in the Herring Gull, and Lesser Black-backed Gulls showed faster population increases at lower Herring Gull densities. Contrasting numbers of gulls nest in coastal habitats or on roofs (mainly in urban habitats). Herring Gulls seem to seek refuge in urban environments, whereas Lesser Black-backed Gulls expand their range into the urban environment. The large declines in hitherto abundant species create a dilemma for conservation bodies in prioritizing conservation policies. The spatial variation in population changes and the differences between species suggest that there is no single cause for the observed changes, thus requiring region-specific conservation management strategies

Instrumentation

published or submitted for publicatio

Sabine's Gull (Xema sabini), Ross's Gull (Rhodostethia rosea) and Ivory Gull (Pagophila eburnea) Gulls in the Arctic: A Review

The earliest information on Sabine's gull, Ross's gull and Ivory gull was collected by several heroic arctic explorers during the nineteenth century and the beginning of the twentieth. Ross's gull was discovered in northern Canada in 1823 by James C. Ross and Sabine's gull in northwestern Greenland in 1818 by Edward Sabine. S.A. Buturlin was the first to find the breeding places of Ross's gull in northeastern Siberia. Recently new breeding places have been reported from U.S.S.R. (Taymyr Peninsula, 1973), Canada (near Devon Island, 1976 and 1978; near Churchill, Manitoba, 1980) and Greenland (Peary Land and Disko Bay, 1979). Sabine's gull and Ivory gull have a dispersed and patchy distribution with gaps too wide for them to be regarded as true continuous circumpolar species. The biotope requirements for the three species are compared. All three are food opportunists; recent data on their food choice and foraging behaviour are reviewed and discussed. The breeding ecology of the gulls is updated with special attention to the clutch size, where a climatological trend may be distinguished. In contrast to birds in general, the most southerly breeding species (Ross's gull) has the largest clutch size and the most northerly breeding species (Ivory gull) has the smallest. Details of the large interspecific differences in migratory and wintering habits are presented. The documented northbound autumn migration of Ross's gull observed in Alaska and the southbound migration of Sabine's gull to western South America and southwestern and southern Africa are surveyed. The Ivory gull is regarded as a straggler during the winter, but recent observations on East Greenland of at least 500 migrating birds in September 1975 indicate that specific migratory routes may be used by this species too

Color Photo Section [March 2011, pp. 3–6]

Peregrine Falcon, Blue-gray Gnatcatcher, Sedge Wren, Spotted Towhee (p. 3); Northern Harrier, Long-eared Owl, Mississippi Kite (p. 4); Loggerhead Shrike, Snow Bunting, Piping Plover, Green Heron (p. 5), Ring-billed Gull with Ross’s Gull, Ross’s Gull, Black-legged Kittiwake, and Lesser Black-backed Gull (p. 6)

Kiters

Robbie is a little disappointed when he gets a home-made kite for his birthday. He would really have liked a computer. But then he gets more than he bargained for with his new kite. Can it help him, though, to find out what is killing the fish and the seabirds and making the sea lose its sparkle? Will Osman, the sleeping giant who lies beneath the Gull Cliff, be able to help? And what about the seagulls who are always hanging around when Robbie and best friend Jace fly their kites? Or the strange old fisherman who seems to be dumping something nasty-looking into the sea? Robbie and Jace are swept into a world of danger, threat and magic as they try to find out what is spoiling their beautiful Gull Cliff Bay

Intercolony Comparison of Diets of Western Gulls in Central California

As human populations expand, they force free-ranging animals to adapt to an increasingly urban environment, resulting in changes in diets, reproductive success, and mortality. The diets of two western gull (Larus occidentalis) breeding populations in central California were compared. One colony, Año Nuevo Island (ANI), is 1 km from shore and within 30 km of a municipal landfill. The other colony, Southeast Farallon Island (SEFI), is located 45 km off the shore of San Francisco, CA. Given the proximity of ANI to the shore and the landfill, I predicted that gulls from ANI would have more garbage in their diets. Indeed, gulls from ANI consumed over three times more garbage. Twenty-three percent of wet diets from gulls at ANI contained garbage, whereas garbage made up only 6% of wet diets from gulls at SEFI. Despite the appearance of garbage in gull diets, birds from both colonies consumed a range of marine prey, and Clupeiformes, Euphausiacea, and Gadiformes were important to both colonies. Isotopic values (15N and 13C) measured in gull feathers were similar between colonies, suggesting that gulls from both populations consume similar prey from the marine environment during the non-breeding phase. The reliance on stable, easily accessible food from landfills during the breeding season may be an important adaptation for western gulls to cope with urbanization and declines in prey species in the California Current during the energy-intensive chick-rearing perio

Identifying habitat-driven spatial variation in colony size of Herring Gulls Larus argentatus

Capsule: Spatial clustering was observed in colony growth rates of three large UK gull species with proxies of local marine and intertidal resources explaining part of this variation in two species. Aims: To investigate spatial clustering in colony growth rates of three gull species and determine which environmental variables may explain any spatial clustering observed. Methods: Colony growth rates were calculated for Herring Gull Larus argentatus, Lesser Black-backed Gull L. fuscus and Great Black-backed Gull L. marinus to identify spatial 2synchrony and to relate to proxies of local foraging conditions in coastal habitats. Results: Spatial clustering in growth rates was found in the gull species. Herring Gull colonies located in areas with greater availability of intertidal prey and fishery activity had higher growth rates. Lesser Black-backed Gull colonies in areas of higher chlorophyll a concentrations experienced more negative growth rates suggesting a negative effect in areas of potential local runoff from agriculture and built-up areas. Conclusion: Spatial clustering in the gulls’ colony growth rates indicated that local colonies did experience similar environmental conditions; helping identify variables influencing coastal populations of two gull species, highlighting the importance of marine habitats. These results highlight the need for species and area-specific management for these species of conservation concern

Color Photo Section [March 2011, pp. 3–6]

Peregrine Falcon, Blue-gray Gnatcatcher, Sedge Wren, Spotted Towhee (p. 3); Northern Harrier, Long-eared Owl, Mississippi Kite (p. 4); Loggerhead Shrike, Snow Bunting, Piping Plover, Green Heron (p. 5), Ring-billed Gull with Ross’s Gull, Ross’s Gull, Black-legged Kittiwake, and Lesser Black-backed Gull (p. 6)