Cuckoos Use Mafia Tactics, And They Work | IFLScience

Brood parasites are organisms that rely on others to raise their young
Photo provided by Flickr

18/04/2014 · Cuckoos Use Mafia Tactics, And They Work

The mafia hypothesis provides an explanation as to why some host birds do not remove parasites' eggs from their nests. The cuckoo lays its eggs in other birds' nests to spare itself the effort of raising its own young. However, some parasitic avian species like the North American brown-headed cowbird (Molothrus ater) or the European great spotted cuckoo (Clamator glandarius) depredate their hosts' nests out of revenge when the hosts do not accept their eggs. Under these circumstances, it makes sense for the host birds to tolerate the additional work involved in raising the cuckoos in the nest to avoid endangering the lives of their own offspring.

It seems some cuckoo species are the ..
Photo provided by Flickr

Meet the Cuckoo Mafia - Inkfish

Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. They are brood parasitic New World birds which are unrelated to the Old World cuckoos, one of which, the common cuckoo, is the most famous brood parasitic bird.
These birds feed on insects, including the large numbers that may be stirred up by cattle. In order for the birds to remain mobile and stay with the herd, they have adapted by laying their eggs in other birds’ nests. The cowbird will watch for when its host lays eggs, and when the nest is left unattended, the female will come in and lay its own eggs. The female cowbird may continue to observe the nest after laying her eggs. If the cowbird egg is removed, the female cowbird may destroy the host’s eggs (see “Mafia hypothesis” for an explanation of this behavior).

25/04/2014 · To find out whether the controversial mafia hypothesis ..
Photo provided by Flickr

There are 2 avian species that have been speculated to portraythis -like behavior, thebrown-headed cowbird of North America, Molothrus ater, andthe of Europe,Clamator glandarius. The Great Spotted Cuckoo lays themajority of its eggs in the nests of the , Pica pica. Ithas been observed that the Great Spotted Cuckoo repeatedly visitsthe nests that it has parasitised, a precondition for the Mafiahypothesis.An experiment was run by Soler et al. from April to July,1990–1992 in the high-altitude plateau Hoya de Guadix, Spain. Theyobserved the effects of the removal of cuckoo eggs on thereproductive success of the magpie, and measured the magpie'sreaction; the egg was considered accepted if it remained in thenest, ejected if gone in between visits, or abandoned if the eggswere present but cold. If any nest contents were gone betweenconsecutive visits, the nests were considered to have beendepredated. The magpie's reproductive success was measured bynumber of nestlings that survived to their last visit, which wasjust before the nestling had been predicted to from the nest. The results from theseexperiments show that after the removal of the parasitic eggs fromthe Great Spotted Cuckoo, these nests are predated at much higherrates than those where the eggs were not removed. Through the useof eggsthat model those of the magpie, it was confirmed that the nestdestruction was caused by the Great Spotted Cuckoo. Thisdestruction benefits the cuckoo, for the possibility of re-nestingby the Magpie allows another chance for the cuckoo egg to beaccepted. Another similar experiment was done in 1996–2002 byHoover et al. on the relationship between the parasiticBrown-headed Cowbird and a host, the ,Protonotaria citrea. In their experiment, they manipulatedthe cowbird egg removal and cowbird access to the predator proofnests of the warbler.They found that 56% of egg ejected nests were depredated upon incomparison to 6% of non-ejected nests when cowbirds were notprevented from getting to the hosts nest. Of the nests that were rebuilt by hosts that had previously beenpredated upon, 85% of those were destroyed.The number of young produced by the hosts that ejected eggs dropped60% compared to those that accepted the cowbird eggs. Althoughthere has not been a lot of performed to test thisso-called "Mafia hypothesis", these two experiments show ratherconvincing results.

When hosts wait for mafia-style retaliation before accepting a cuckoo egg, mafia ..
Photo provided by Flickr