To help birds in areas of declining natural habitat find desirable spots to replace missing tree cavities to lay their eggs, conservation biologists often erect wooden boxes. But they have discovered that the practice might actually hurt some bird species. With wood ducks, for example, as many as eight females may attempt to lay eggs in a single nest, parasitizing each other's eggs to do so. High density and visibility of the nest boxes were thought to cause such behavior. Now, however, UC Davis and other researchers have found that other cavity-nesting birds, such as Barrow's goldeneyes, which tend to be highly territorial, do not experience an increase in parasitized nests in the wood boxes, nor is goldeneye reproductivity threatened. In comparing wood ducks and goldeneye ducks, UC Davis assistant professor of wildlife, fish and conservation biology John Eadie and his colleagues realized that the social behavior of different species of cavity-nesting birds must be understood better when conservation plans are designed. "In changing the habitat resources, we are changing something fundamental to their biology. Without better information on how we are affecting the social interactions of our target species, we run the risk of making the situation worse," Eadie says. The studies of the wood ducks and goldeneye ducks are included in the book, "Behavioral Ecology and Conservation Biology" (Oxford University Press), edited by Tim Caro, also a UC Davis professor of wildlife, fish and conservation biology. It will be published later this year.