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How do Common Gulls [Larus canus] pass through Copenhagen on migration?

100%

Pedersen K. T. , Fritze E. B. , Kharitonov S. P.

The Ring

1999

tom 21

nr 2

Site parameters’ variance – a missing dimension in the studies of nest-site selection?

84%

Skorka P. , Martyka R. , Wojcik J. D. , Lenda M.

Polish Journal of Ecology

2011

tom 59

nr 2

In most studies of nest-site selection the data of habitat parameters are treated with analysis of variance. A basic assumption of this test is the homogeneity of variance. Here, we show that the nest-site selection process leads to lower variance of the selected parameters than in the case of random points which generally describe the available average characteristics of the environment. Thus, the variance should be accounted for in studies on nest-site selection and it should be treated not as a problem (as it is usually done), but as a source of additional important information on the selection process. Comparison only of mean values often does not lead to significant differences between nest site parameters and random points which may result from a small effect size (when animals select features similar to the general mean of available characteristics). Deeper insight into variance of the site parameters may elicit important results. We illustrate this issue with real data on nest site (islets and shores of water reservoirs) selection in the Common Gull Larus canus. Four (islet’s area, vegetation height on islets, vegetation cover on shore and distance to nearest shrub or tree on shore) from eight parameters were favored by the birds and, as predicted, their variance values were lower than of those not selected (vegetation cover on islets, distance of the islets to shoreline, vegetation height on shore and distance to water).

Habitat and nest site selection in the Common Gull Larus canus in southern Poland: significance of man-made habitats for conservation of an endangered species

67%

Skorka P. , Martyka R. , Wojcik J. D. , Babiarz T. , Skorka J.

Acta Ornithologica

2006

tom 41

nr 2

The species composition and the age structure of Gulls wintering in the selected places of the Gulf of Gdansk

67%

Meissner W. , Nitecki C.

The Ring

1999

tom 21

nr 2

Dioksyny i furany [PCDD-Fs] w ptakach morskich z poludniowej czesci Morza Baltyckiego

42%

Falandysz J. , Bergqvist P. A. , Rappe C.

Bromatologia i Chemia Toksykologiczna

1998

tom 31

nr 1

75-78

Oznaczono stężenie polichlorowanych dibenzo-p-dioksyn (PCDDs) i polichlorowanych dibenzofuranów (PCDFs) w tkankach trzech grup ptaków morskich - wszystkożernych (mewa pospolita Larus canus), rybożernych (nur rdzawoszyi Gavia stellata, alka krzywonosa Alca torda, nurzyk podbielały Uria aalge) i drapieżnych (bielik Haliaeetus albicilla), z części południowej Morza Bałtyckiego. 2,3,4,7,8-penta-CDF i 1,2,3,7,8- penta-CDD wykryto w największym stężeniu, a w mniejszym wiele innych mniej toksycznych PCDDs i PCDFs.

PCDDs and PCDFs have been determined in the adipose tissue, liver or breast muscle of a few marine birds, including mixed-feeders (common gull), fish-eaters (redthroated diver, razorbill, guillemot) and predator species (sea eagle) collected from the south coast of the Baltic Sea. High levels of 2,3,4,7,8-penta-CDF and 1,2,3,7,8-penta-CDDD as well as of numerous less toxic PCDD/Fs were found in all samples. A relationship could be observed between the position of the test species in the food chain and body lipids PCDD/Fs concentrations, which were lower for the common gull than for a typical fish-eater and highest in the white-tailed sea eagle.