![]() ![]() In Southern Finland, common cuckoos often parasitize common redstarts with deceptive color-matched eggs. In the summer of 2014 they conducted two experiments. At the same time, North American brown-headed cowbird males and females have been reported with increased frequency in Western Europe, often in association with storm events.ĭinets and his colleagues wondered how naïve North American birds would respond to brood parasitism by common cuckoos, and how Eurasian birds would respond to eggs from brown-headed cowbirds. In 2012 one common cuckoo overwintered in California. Vagrant cuckoo sightings have been recorded in mainland Alaska and its archipelagos, including one common cuckoo pair observed in courtship, plus multiple specimens collected locally by the University of Alaska’s Museum of the North. Having now colonized northeastern Siberia, both cuckoo species now breed within 300 kilometers of the Bering Strait, according to Russian museum records examined by Dinets and his colleagues. All have begun showing up far from home.Īlthough there are signs that common cuckoo populations are declining in Europe, the common and Oriental cuckoo species, native to temperate Eurasia, appear to be expanding their ranges northward. These egg sneaks include the Eurasian common cuckoo, the Oriental cuckoo, and the brown-headed cowbird. Dinets and Hauber study brood parasites, species that foist their eggs on unwitting foster species by sneaking them into a host’s nest, saving themselves the effort of rearing chicks and reducing breeding success of the hosts they dupe in the process. Records of three such wanderers recently prompted animal behaviorists Vladimir Dinets of the University of Tennessee, Mark Hauber of Hunter College and their colleagues to investigate the possible future impacts of such cross-oceanic invasions. Unlike “normal” migrants, they are very often on a one-way trip. That raises an important point about vagrants. As meteorological conditions change over the oceans, birds that are crossing the Gulf of Mexico may be increasingly likely to get caught by the winds, and “deported to the Atlantic,” with the few survivors ending up in Europe, he explains. “Vagrancy is condition-dependent, which can also be linked to climate change,” Jiguet says. Conversely, his data suggest that shrinking populations produce fewer vagrants. In a 2013 study, he found that as populations expand, so, too, do the number of vagrants detected far from home. Veit has described vagrants as the expanding fringe of a growing population.įrédéric Jiguet of the Center for Ecology and Conservation Sciences* in Paris, France, has been examining links between climate change, range shifts and Siberian birds found as vagrants in Europe. ![]() “In any population there are always a small proportion of individuals that go much farther than the others,” he says. Veit frames vagrancy as part of the overall spectrum of bird dispersal. He and his student Lucinda Zawadzki are now mining predictive hints from vagrancy data for the ash-throated flycatcher. ![]() According to ecologist Richard Veit of College of Staten Island at the City University of New York, that notion that all vagrants are “messed up, and unable to navigate,” has led people to ignore their potential importance in understanding animal distributions and how they change over time. In truth, vagrants may not necessarily be the oddballs that observers have assumed them to be. Other vagrants apparently veer way the wrong way, or overshoot their target due to navigation-impeding genetic mutations. In autumn, North American species are sometimes found as vagrants in Europe, often in association with storms. Vagrants have traditionally been perceived as unlucky birds blown off course by severe weather during migration, or dud birds with faulty internal GPS. Now scientists are beginning to consider the possibility that these misplaced birds might be more than curiosities, exploring the question of whether vagrants could provide clues about future bird distributions as climate shifts. Wildlife tours of the Alaskan archipelago, for example, lure customers with the possibility of sighting exotic vagrants like the Eurasian common cuckoo. Birds that show up outside of their normal range-vagrants or accidentals, as they are known, have long fascinated birdwatchers. ![]()
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