Studies of unhanded Mexican Jays (Aphelocoma ultramarina), which began with Gross (1949), Wagner (1955) and Hardy (1961), reported the presence of more than two birds around nests and hinted at cooperation. The first intensive study based on color-banding of entire flocks, however, revealed mainly uncooperative rivalry (Brown 1963a). Here, we summarize published knowledge of the behavioral ecology of this species and discuss the apparent contradiction of the presence in the same social units and even the same individuals of both cooperative and uncooperative behavior. A more detailed report covering 20 years of data is currently in preparation.

Habitats and study areas

We have studied Mexican Jays at three principal localities in the United States and a variety of places in Mexico. We began our work in the Santa Rita Mountains of Arizona in 1958. For our long-term study beginning in 1969, however, we chose a base at the Southwestern Research Station of the American Museum of Natural History in the Chiricahua Mountains of Arizona, working with A. u. arizonae. To gain information about other subspecies we have made brief studies in the Chisos Mountains of Texas and in the Sierra Madre of Mexico. Thus, most of our work has been done on A. u. arizonae, but we have some field data on nearly all the other subspecies.

Mexican Jays throughout their range are typically associated with temperate-zone oaks (Quercus spp.) and mountains.