Cases of occasional interspecific brood parasitism and egg dumping in Hungary

There are numerous publications in the ornithological literature on mixed-species broods, i.e. on cases when a species lays some or all of its eggs into the nests of other species. This phenomenon, known as brood parasitism, has not yet been studied in Hungary. Here, I use the term brood parasitism, but I could not separate cases of egg dumping, a reproductive error by females. Based on literature and my own observations, I found evidence for interspecific brood parasitism in 28 species breeding in Hungary, not including the cases of the obligate interspecific brood parasite, the Common Cuckoo (Cuculus canorus). Only one of these belongs to passerines, while in the rest of the cases, this phenomenon occurred in representatives of non-passerine families. However, cases of brood parasitism and nest parasitism have to be treated separately. The latter refers to cases when a species occupies a nest, usually a nesthole or nestbox, already containing eggs of another species, and lays its own eggs next to the foreign eggs. The present study provides data on European Roller (Coracias garrulus), Northern Goshawk (Accipiter gentilis), Common Kestrel (Falco tinnunculus), Red-footed Falcon (Falco vespertinus), Eurasian Hobby (Falco subbuteo), tit species (Parus, Cyanistes, Poecile spp.), Eurasian Nuthatch (Sitta europaea) and Eurasian Tree Sparrow (Passer montanus), but in all likelihood the number of species involved is much higher.

Diversity of social-genetic relationships in the socially monogamous pied flycatcher (Ficedula hypoleuca) breeding in Western Siberia

We explored the genetic background of social interactions in two breeding metapopulations of the pied flycatcher (Ficedula hypoleuca) in Western Siberia. In 2005, we sampled blood from birds breeding in study areas located in the city of Tomsk and in a natural forest 13 km southward of Tomsk (Western Siberia, Russia). We sampled 30 males, 46 females, 268 nestlings (46 nests) in the urban settlement of pied flycatcher, and 232 males, 250 females, 1,485 nestlings (250 nests) in the woodland plot. DNA fingerprinting was carried out using eight microsatellite loci, which were amplified by two multiplex-PCRs and analyzed by capillary electrophoresis. About 50–58% of all couples were socially and genetically monogamous in both study plots. However, almost all possible social and genetic interactions were detected for non-monogamous couples: polygamy, polyandry, helping, adoption, and egg dumping. Differences in the rate of polygyny and the rate of extra-pair paternity between both study sites could be explained by differences in environmental heterogeneity and breeding density. Our findings suggest that egg dumping, adoption, polygamy, extra pair copulation, and other types of social-genetic interactions are modifications of the monogamous social system caused by patchy environment, breeding density, and birds’ breeding status.

Egg laying in inappropriate nests by the Brown-headed Cowbird (Molothrus ater): acts of parasitism or emergency egg dumping?

The generalist, brood-parasitic Brown-headed Cowbird (Molothrus ater) has been found to parasitize the nests of about 220 species, mostly passerine birds. Among the thousands of documented cases of parasitism are rare records of egg laying in nests in which the cowbird stands no chance of success, because its diet or developmental strategy are incompatible with those of the “host” species. Forty-four nests of 16 such inappropriate host species are reviewed: 23 nests of nine precocial species (waterbirds and shorebirds) plus 21 nests of seven altricial species (a raptor, doves, cuckoos, a hummingbird, and a woodpecker). Two hypotheses explain inappropriate egg laying. In the “normal laying” hypothesis, Brown-headed Cowbirds may lay dozens of eggs in nests they encounter, including the occasional inappropriate nest. In the “emergency laying” hypothesis, females, on discovering that a selected nest has failed, must lay or “dump” her eggs elsewhere, in nests of inappropriate hosts or already-parasitized nests of regular hosts. Support for either hypothesis will require electronic surveillance of movements of nest-searching and laying Brown-headed Cowbirds to generate fine-scale spatial data that confirm whether parasitism on inappropriate nests occurs at the usual laying time for pre-selected nests (around sunrise) or later in the day if the chosen nest has failed and emergency laying is required.