Reply from R. Winfree

Abstract

For reasons of space, my recent TREE review article1xCuckoos, cowbirds and the persistence of brood parasitism. Winfree, R. Trends Ecol. Evol. 1999; 14: 338–343Abstract | Full Text | Full Text PDF | PubMed | Scopus (52)See all References1 was limited to obligatory interspecific brood parasitism. As Meyer-Rochow points out, intraspecific parasitism is a different phenomenon and will probably have different dynamics2xLaying eggs in others’ nests: intraspecific brood parasitism in birds. Petrie, M. and Moller, A.P. Trends Ecol. Evol. 1991; 6: 315–320Abstract | Full Text PDF | PubMed | Scopus (112)See all References2. For example, in extending the cost–benefit approach to the intraspecific case, the net effect of parasitism on both the host and the parasite has to be considered, because it is no longer true that the parasite is unable to raise its own young. One possible result of this is that the fitness of parasitic behavior within a species becomes frequency-dependent3xCould intraspecific brood parasitism cause population cycles?. May, R.M. et al. : 1012–1022See all References3.Regarding anatids and precocity, the question is: why is facultative, intraspecific parasitism common among precocial species (91.5% of 117 species studied)4xThe distribution of conspecific nest parasitism in birds. Rohwer, F.C. and Freeman, S. Can. J. Zool. 1989; 67: 239–253CrossrefSee all References4 and obligatory, interspecific parasitism uncommon (1 of 968 existing species, or 0.1%)5xA survey of modern birds. Brooke, M.de L. : 85–120See all References, 6xDevelopment of behavior in precocial birds. Nice, M.M. Trans. Linn. Soc. New York. 1962; : 20–21See all References, 7xAvian brood parasitism. Payne, R. : 338–369See all References, whereas the reverse is true for altricial species, with intraspecific parasitism being comparatively rare (32.7% of 101 species studied)4xThe distribution of conspecific nest parasitism in birds. Rohwer, F.C. and Freeman, S. Can. J. Zool. 1989; 67: 239–253CrossrefSee all References4 and obligatory interspecific parasitism relatively common (92 of 8272 existing species, or 1.1%)5xA survey of modern birds. Brooke, M.de L. : 85–120See all References, 6xDevelopment of behavior in precocial birds. Nice, M.M. Trans. Linn. Soc. New York. 1962; : 20–21See all References, 7xAvian brood parasitism. Payne, R. : 338–369See all References?I do not know the answer to this question, but several factors might contribute to these differences. First, relative to altricial species, precocial species provide little parental care, lowering both the host’s cost of parasitism and the parasite’s benefit from it8xWhy is conspecific nest parasitism more frequent in waterfowl than in other birds?. Sorenson, M.D. Can. J. Zool. 1992; 70: 1856–1858CrossrefSee all References, 9xWhy is conspecific nest parasitism more frequent in waterfowl than in other birds: a reply to M.D. Sorenson. Rohwer, F.C. and Freeman, S. Can. J. Zool. 1992; 70: 1859–1860CrossrefSee all References. Second, precocial species lay relatively ‘costly’ eggs, which presumably increases the cost to the parasite of unsuccessful parasitism9xWhy is conspecific nest parasitism more frequent in waterfowl than in other birds: a reply to M.D. Sorenson. Rohwer, F.C. and Freeman, S. Can. J. Zool. 1992; 70: 1859–1860CrossrefSee all References9. Third, because precocial species have larger clutch sizes, marginal analysis suggests that the percent benefit of laying an extra (parasitic) egg is less for precocial species10xMode of development and interspecific avian brood parasitism. Lyon, B. and Eadie, J.M. Behav. Ecol. 1991; 2: 309–318Crossref | Scopus (33)See all References10. Lyon and Eadie10xMode of development and interspecific avian brood parasitism. Lyon, B. and Eadie, J.M. Behav. Ecol. 1991; 2: 309–318Crossref | Scopus (33)See all References10 provide a clear formulation of these costs from the parasite’s point of view. Finally, a more thorough investigation of this subject would need to count the number of precocial and altricial species more carefully (I excluded some groups which were not clearly in either category) and also to correct for phylogenetic non-independence.Like Meyer-Rochow, I find Smith’s11xThe advantage of being parasitized. Smith, N.G. Nature. 1968; 219: 690–694Crossref | PubMed | Scopus (55)See all References11 example of beneficial parasitism interesting. However, I didn’t discuss it in my review because later studies in other parts of the giant cowbird’s range12xForaging ecology and host relationships of giant cowbirds in southeastern Peru. Robinson, S.K. Wilson Bull. 1988; 100: 224–235See all References, 13xInterspecific brood parasitism of Montezuma oropendolas by giant cowbirds: parasitism or mutualism. Webster, M.S. Condor. 1994; 96: 794–798CrossrefSee all References haven’t been consistent with parasitism being beneficial, thus it seems unlikely that this is one of the main forces allowing parasitism to persist.