
... parasitize the nest. The most remarkable thing about cuckoo parasitism is the birds' ability to match the eggs of the host species in size, spottedness, background color, and darkness. The eggs of all five species commonly parasitized in Britain are much smaller than a bird the size of the cuckoo would normally lay; but the cuckoo still manages to lay eggs of just the right size. When the bona fide eggs of the five parasitized species are placed side-by-side with the mimics layed by the cuckoos, the matches are uncanny - except in the case of the dunnock, which the cuckoo doesn't try to mimic at all. The question, of course, is how the cuckoos do it. American cuckoos rarely parasitize the nests of other birds; but the American cowbird is notorious in this regard, although it does not indulge in egg mimicry. On other continents, cuckoos, honeyguides, finches, a weaverbird, and a duck have learned how to slough off parental duties. (Brooke, M. de L., and Davies, N.B .; "Egg Mimicry by Cuckoos Cuculus canorus in Relation to Discrimination by Hosts," Nature, 335:630, 1988. Also: Harvey, Paul H., and Partridge, Linda; "Of Cuckoo Clocks and Cowbirds," Nature, 335:586, 1988.) From Science Frontiers #61, JAN-FEB 1989 . 1989-2000 William R. Corliss ...
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... Science Frontiers ONLINE No. 119: Sep-Oct 1998 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Murder In The Nest In a recent issue of BioScience, R.B . Payne authored an excellent review of brood parasitism in birds. Brood parasites lay their eggs in the nests of other species, which then incubate the eggs and raise the alien chicks. The parent parasites are thus free to forage, hang out, and parasitize more nests. Brood parasitism is such a successful and easy way of life that 136 species of cuckoos, 5 species of cowbirds, 20 finches, and South America's Blackheaded Duck have adopted it. Brood parasitism fascinates ornithologists because it involves war between the parasites and their hosts. Since host species may eject parasite eggs or fail to nurture parasite chicks, brood parasites have evolved mimicry as a powerful weapon in these battles. Mimicked are host eggs, host nestlings, and host vocalizations. But the most insidious weapons of all involve the outright murder of host chicks. To this end, parasite chicks have evolved some special weapons and behaviors. Some cuckoo chicks evict host eggs or chicks by squirming under them and positioning them in a specially configured hollow on their backs. Then, pushing upward and outward to the rim of the nest, they dump their cargo over the edge. Other brood parasites are more direct and bloodthirsty. "Nestling African honeyguides have bill hooks to stab and kill their nestmates and the brood parasitic American striped cuckoos have independently evolved hooks and pincers to kill." (Payne ...
Terms matched: 1 - Score: 15 - 15 May 2017 - URL: /sf119/sf119p04.htm