Schwemmer P.,University of Kiel |
Halterlein B.,National Park Administration Wadden Sea Schleswig Holstein |
Geiter O.,Institute for Avian Research |
Gunther K.,Schutzstation Wattenmeer E.V. |
And 2 more authors.
Waterbirds | Year: 2014
Strong winters may increase mortality in avian species, with potentially severe consequences for populations. A period of 10 cold days during an otherwise mild winter occurred in the Wadden Sea during February 2012, causing a mass mortality of more than 1,100 Eurasian Oystercatchers (Haematopus ostralegus). This study investigated whether mortality was highest in certain bird-classes (sex, age, diet specialization). By comparing dead with live individuals captured before and after the cold spell, significantly more immature Eurasian Oystercatchers were found dead (> 60%) than expected. Sex ratio did not differ significantly between dead and live individuals, the proportion of males being higher in both dead and live birds. All the dead individuals collected showed significantly smaller body masses (overall mean: 324 g) than live ones (overall mean: 457 g). Few individuals showed internal lesions or anatomical abnormalities, and no influenza virus was found. Dead Eurasian Oystercatchers had completely empty stomachs in 25% and 37% of the individuals in both study areas, Büsum and Amrum, respectively; all other individuals showing only few prey remains. The most frequent prey items were common cockles (Cerastoderma edule). Based on bill shapes, most of the dead Eurasian Oystercatchers were bivalve specialists, and fewer than expected worm eaters died. From band recoveries (n = 19), many of the dead individuals originated from Scandinavia (37%). The main reason for the high mortality appeared to be low food availability and quality before the cold spell combined with sudden low temperatures. © 2014, Waterbirds Society. All rights reserved.
Arizaga J.,University of Navarra |
Arizaga J.,Institute for Avian Research |
Belda E.J.,Polytechnic University of Valencia |
Barba E.,University of Valencia
Journal of Ornithology | Year: 2011
Meteorological conditions, fuel load and date in the season can affect the departure decisions among migratory birds. However, it is poorly understood to what extent the departure decisions are more influenced by some parameters in relation to others, and how they interact with each other. We explored here how fuel load, date, rain and wind (measured on the ground and at high altitude, codified as a tailwind component) influenced the departure decisions of migratory Blackcaps (Sylvia atricapilla) from a stopover site. We used mark-recapture data of 947 Blackcaps collected during the autumn migration period 2005 at a stopover site in northern Iberia, estimating the emigration likelihood with Cormack-Jolly-Seber models, in which we tested for the effect of these four study variables. Best models fitting data showed an additive and positive effect of tailwind and fuel load on the emigration likelihood. © 2011 Dt. Ornithologen-Gesellschaft e.V.
Delingat J.,Institute for Avian Research |
Hobson K.A.,Environment Canada |
Dierschke V.,Institute for Avian Research |
Schmaljohann H.,Institute for Avian Research |
Bairlein F.,Institute for Avian Research
Journal of Ornithology | Year: 2011
Linking events of breeding, wintering and stopover areas has important ecological and conservation implications for migratory species. To find a tool to connect these different events in a long-distance migrating songbird, the Northern Wheatear Oenanthe oenanthe, we applied a discriminant analysis based on morphometrics and analysed stable isotope values (δ13C, δ15N, δD) in feathers. Morphometric differences were additionally analysed with respect to wing shape as an adaptation to migration routes. Discriminant analysis 100% separated a group of long-winged migrants passing the German offshore island of Helgoland from Icelandic and Norwegian breeding birds, as well as from Northern Wheatears passing the Baltic Sea coast on migration. This clear assignment suggests a Greenlandic origin of these long-winged Northern Wheatears. The most likely Greenlandic origin was further supported by depleted δD values in feathers of these birds grown on the breeding grounds. We found a relatively high proportion of presumed Greenlandic birds on Helgoland and especially on Fair Isle (Scotland) during spring migration. Morphometric differences were based mainly on wing morphology and could be successfully connected with migration routes. Presumed Greenlandic Northern Wheatears showed more pointed wings than birds from other European breeding areas. Such wings might be natural selection's solution for the long obligatory non-stop flights during the Atlantic crossings. © 2010 Dt. Ornithologen-Gesellschaft e.V.