Responses of Black-headed Gulls Larus ridibundus to conspecific brood parasitism |
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Authors: | Radka Le?alová-Piálková and Marcel Honza |
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Institution: | (1) Institute of Vertebrate Biology Academy of Sciences of the Czech Republic, Květná 8, 60365 Brno, Czech Republic;(2) Department of Zoology, Faculty of Biological Sciences, University of South Bohemia, Branišovská 31, 37005 Ceske Budejovice, Czech Republic |
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Abstract: | Conspecific brood parasitism in birds occurs when a female inserts her egg into the clutch of her own species. If successful,
i.e. the parasitic egg is accepted by the host, then the host female or pair rears the offspring of the parasite. In the present
study, we studied natural conspecific brood parasitism in Black-headed Gulls (Larus ridibundus), and conducted series of the experiments with mimetic (conspecific) and non-mimetic (conspecific painted light blue) eggs
to explore responses of the tested pairs towards these alien eggs. The natural parasitism rate was 10% and the probability
of being parasitized significantly increased with nest density. Experimentally parasitized pairs rejected both types of experimental
eggs at a similar rate: 14.3 % for mimetic and 25.5% for non-mimetic within 2 days. Non-mimetic eggs were more selectively
rejected than mimetic eggs. The relationships between the probability of egg rejection (dependent variable) and predictor
(independent) variables were examined by fitting generalized linear models. Contrast and intraclutch variation in ground color
and spotting pattern and the volume of the egg had no significant effect on rejection behavior in either non-mimetic or mimetic
eggs. However, nest density significantly positively affected rejection behavior of the Black-headed Gulls in both non-mimetic
and mimetic treatments. |
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Keywords: | Black-headed Gull Egg rejection Experiment Intraspecific brood parasitism Larus ridibundus |
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