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We studied patterns of extra-pair maternity (EPM) in 245 nests (225 nests belonging to 120 females of known identity) of sexually promiscuous European barn swallows ( Hirundo rustica rustica) over a 3-year period. At least one EPM nestling was identified in 54 nests (22.0 %), representing 5.7 % of a total of 1060 nestlings. Up to 28.3 % of all EPM nestlings resulted from quasi-parasitism (QP), whereby nest-attending males sired parasitic offspring. Nests of quasi-parasitic females were never in close proximity to the host nest. Our data thus indicate nonrandom QP patterns in our population suggesting that QP can be considered a third alternative reproductive strategy alongside extra-pair paternity (EPP) and intraspecific brood parasitism (IBP). Of several socioecological factors evaluated, only number of simultaneous egg-laying females in the population proved a good predictor for EPM occurrence. Whereas parasitic females produced more offspring per breeding attempt than was the population average, both QP and IBP affected host female reproductive output, being associated with a reduced number of her offspring produced from the nest. On the contrary, QP resulted in an increase in the number of offspring produced by nest-attending males, suggesting that males may benefit from cooperating with parasitic females at the expense of their social partners. [ABSTRACT FROM AUTHOR]

This article discusses a study which examined temporal changes in parasitism rate by the Common Cuckoo on one of its regular hosts, the Red-backed Shrike Lanius collurio. In the Czech Republic, the Red-backed Shrike is one of the most commonly ringed bird species. The parasitism rate in this study was calculated by administrative districts within the country. Results of the study showed that there was a mean parasitism rate of 1.04% during 1964-2006. The study also found a significant drop in the parasitism rate of Shrike nests during the same period. It also identified two districts with the highest rates of parasitism.