Avian nest-site selection and nesting success in two Florida citrus groves

We studied nesting success and nest-site selection of Common Ground-Doves (Columbina passerina), Northern Mockingbirds (Mimus polyglottos), Brown Thrashers (Toxostoma rufum), and Northern Cardinals (Cardinalis cardinalis) in two Florida citrus groves in spring 1989. Predation resulted in the loss of more than half of all nests. Fish Crows (Corvus ossifragus) and rat snakes (Elaphe obsoleta) seemed to be the major predators. Nesting success differed between groves and may have resulted from differences in human activities, predator populations, or vegetation structure. Nesting success of Northern Cardinals and Brown Thrashers was lower than that reported in other studies and may have been below the replacement level. Northern Mockingbirds had the most open nest sites with the largest inter-canopy distances (spacing between tree canopies), whereas Brown Thrashers seemed to select areas of the groves with the greatest canopy closure. Northern Cardinals tended to select nest trees with full canopies, perhaps to increase nest concealment. Common Ground-Dove nests were supported by limbs with small angles (degrees deviation from horizontal) and the largest diameters.