1991/08/01 by Bridget J. M. Stutchbury, Bridget J. Stutchbury
Agricultural and Biological Sciences · #Botanical Research and Applications #Plant and animal studies
paper · doi:10.2307/1368198
Purple Martins (Progne subis hesperia) breeding in natural cavities in saguaro cacti did not form dense colonies, unlike martins (Progne subis subis) that breed in nesthouses in eastern North America.However, nests were clumped on a larger geographic scale.Birds in these groups of nests quickly formed mobs of up to 10 birds in response to a model crow at the nest.Males and females defended an area around their nest cavity with a radius of about 20-30 m, and often defended cavities other than the nesting cavity.Only 5-l 5% of breeding males were subadults and some subadult males defended cavities without a mate, indicating that many subadult males did not breed as one-year-olds.A literature review of martin colony sizes in natural cavities indicates that nest-house colonies fall within the range of breeding densities to which martins were exposed historically.The many similarities in breeding biology and social behavior between this desert subspecies and nesthouse populations suggest that nest-houses are appropriate models of natural conditions.