Last year, the American Ornithologists’ Union changed the format of its Ornithological Monographs series. Originally a full-length work, published at irregular intervals, the new format consists of shorter articles, published quarterly. The most recent volume in the series is Management of Cowbirds and Their Hosts: Balancing Science, Ethics, and Mandates, edited by Catherine P. Ortega, Jameson F. Chace, and Brian D. Peers.

Brood parasites, Cowbirds in particular, have attained a reputation as savage creatures, who will kill the young of other birds to advance their own. While many of the stories of cruelty are overblown, cowbirds do, indeed, threaten the populations of many other species of birds. Population reductions in many songbirds throughout the U.S. are attributed to brood parasitism, and people are fighting back. Parasite management programs have resulted in the killings of thousands of cowbirds and other parasites each year. The effect on endangered species, however, is variable, so is this a noble act or a questionable practice? When does it become acceptable to kill off one species of bird in order to protect another? This new monograph offers an excellent analysis of the problems faced by modern bird management professionals, by offering the results of several cowbird management programs, and analyzing the results.

In brood parasitism, a parasite bird will lay its eggs in the nest of a host bird, which will incubate the parasitic eggs and raise the young as if they were its own. (Ortega) Nonobligate brood parasites may lay their eggs in the nests of other species, conspecifics, or even their own nests. Obligate brood parasites, like the Brown-headed Cowbird, on the other hand, cannot raise their own young. Their parasitic tendencies are so evolved that they no longer have the physical or instinctual ability to incubate or rear their own young.

The costs to host species of parasitism by Cowbirds varies. Some raise a mixed brood of cowbirds and their own young, while some end up fledging no young of their own. (Rothstein) The reasons are due to the highly evolved behavior and biology of the parasite. Parasite birds, while laying an egg, may remove one or more host eggs to make room for its own. The intrusion by the cowbird frequently results on the desertion of the nest by the host bird. If the host stays, the short incubation time of cowbirds means that the eggs may be denied the incubation time they need, or the young birds may not receive enough food.

These actions affect the breeding success of many songbirds, and many management programs have been put in place to protect them.

Modern management techniques stress trapping and shooting. Success of these management programs varies greatly, making it difficult to assess the results. Some programs show great conservation success due to cowbird control, while others saw very little impact. The articles in this monograph, by a host of experts, attempt to synthesize the information into a better understanding of the management options and their impacts. Articles explain the biology and behavioral ecology of the Brown headed Cowbird, and factors affecting their distribution and abundance. Three Cowbird control programs are described and interpreted. Other articles discuss research directions, host defenses, controversies and conservation solutions.

How overpopulated does one species have to be, and how threatened does another species need to be to justify these extreme measures? How do we balance these questions in our role as nature caretaker? This monograph offers an enlightening discussion on the programs, their successes and failures, with fascinating discussions about the controversies to help you make your own decisions.

Management of Cowbirds and Their Hosts: Balancing Science, Ethics, and Mandates. Catherine P. ORTEGA, Jameson F. CHACE, and Brian D. PEER, Editors. American Ornithologists’ Union, 2005. Ornithological Monographs No. 57. 114 pp. Paper. $10.00

Other resources on Cowbirds and other Brood Parasites:

FRIEDMANN, Herbert & L. F. KIFF. The Parasitic Cowbirds and their Hosts. Western Foundation of Vertebrate Zoology, 1985. Pp. 225-304. Paper. $12.50

MORRISON, M.L., et al, Editors. Research and Management of the Brown-headed Cowbird in Western Landscapes. Proceedings of a Symposium held in Sacramento 23-25 October 1997. Cooper Studies in Avian Biology No. 18, 1999. 312 pp. Paper. $20.00

ORTEGA, Catherine. Cowbirds and Other Brood Parasites. University of Arizona Press, 1998. A comprehensive study, including assessment of their threat to songbirds. 371 pp. $65.00

SMITH, James N., Terry L. COOK, Stephen I. ROTHSTEIN, Scott K. ROBINSON, and Spencer G. SEALY, Editors. Ecology and Management of Cowbirds and their Hosts: Studies in the Conservation of North American Passerine Birds. University of Texas Press, 2000. 388 pp. $85.00

DAVIES, Nick. Cuckoos, Cowbirds and Other Cheats. Princeton, 2000. Illustrations by David QUINN. The evolution and natural history of brood parasites and host defenses; a worldwide survey. 310 pp. $29.95

Also see the Passeriformes section for more.