Ecology of the plain chachalaca in the lower Rio Grande Valley of Texas

Abstract

The life history, pesticide residue levels, extent of habitat reduction, and status of the plain chachalaca, Ortalis vetula mccalli, were investigated in the Lower Rio Grande Valley of Texas during 1971 and 1972. The main study area was Santa Ana National Wildlife Refuge, but additional data were obtained from three other study areas in the region. Plain chachalacas consumed a variety of succulent plant material and little animal matter. Berries and seeds were major food items eaten in spring and fall when they were abundant. When availability of berries and seeds was low during winter and summer, leaves and buds were relatively more important in the diet. Movements were commonly associated with availability of natural foods. Movements were usually of short distance; over 75 percent of the marked birds observed traveled less than 0.4 km. The reproductive potential of this species is lower than many other gallinaceous game birds. Mean clutch size for 47 incubated nests was 2.7 eggs. Thirty-nine percent of 59 active nests examined in 1971 successfully fledged young. Of the unsuccessful nests, 54.2 percent were destroyed and 6.8 percent were apparently abandoned. Most nest destruction was apparently caused by mammalian predators, snakes, and wind. In 1971, hatching success of 38 incubated nests was 51.4 percent. Average number of fledglings per successful nest (N=23) was 2.3. ...