, of course, is but one variant on the nonsymbiotic relationship between species, both animals and plants, in which one benefits at the expense of the other.
It is interesting that bronzed cowbirds responded frequently to Altamira oriole songs, since Altamira orioles resist brood parasitism
and seldom raise bronzed cowbirds (Hathcock, 2000; Werner et al.
Thus, we hypothesized certain species might be more susceptible to brood parasitism
and subsequently nest failure than others.
by Brown-headed Cowbirds, WNV infection, loss of wintering habitat of neotropical migrants, and habitat degradation and loss on breeding ranges are all factors acting on populations of North American birds (Terborgh 1989, Causey and others 2003).
Some types of adoption in mammals may be similar to brood parasitism
in birds (see, for example, Nicolson, 1987; Hrdy, 1979).
As a result, birds that were attracted to playback sites in this area had low brood parasitism
rates and high nesting success (Ward & Schlossberg 2004).
Impact of brood parasitism
by brown-headed cowbirds on red-winged blackbird reproductive succes.
Nest depredation and brood parasitism
are known to increase in habitat fragments, which decrease productivity of birds.
Each account includes a range map; a capsule statement identifying key components for managing habitat for the species; a table of habitat requirements organized by author and state or province; sections on suitable habitat, area requirements, brood parasitism
, breeding-season phenology, species' response to management, and management recommendations; and literature cited.
Suspected causes of this decline are many and include habitat loss and fragmentation in wintering and breeding areas; climatic changes; brood parasitism
by cowbirds; habitat alteration by increasing numbers of white-tailed deer and loss of important stopover points during migration.
For instance, adults spend less time guarding their nests when food is in short supply so nest predation and brood parasitism
occur more frequently (Yom-Tov 1974, Arcese and Smith 1988, Ward and Kennedy 1996).
The PIH was a tenable hypothesis during the early phase of my study because evidence showed that (a) nestlings in broods of five often starved (Murphy 1983b), (b) kingbirds accept foreign eggs from conspecifics (Bischoff and Murphy 1993), and (c) intraspecific brood parasitism
occurs (McKit rick 1990).