Present use and characteristics of Thick-billed Parrot nest sites in northwestern Mexico

Thick-billed Parrot (Rhynchopsitta pachyrhyncha) nest sites were studied during a six-year period (1995-2000) at six nesting areas in the Sierra Madre Occidental in Mexico. Nests were found in 187 snags or live trees of seven species, which averaged 75.2 cm dbh. Most nests were in snags (59%), and only two nests occurred in trees or snags under 40 cm dbh. Most nests occurred in Douglas fir (Pseudotsuga menziesii 32.6%), and Mexican white pine (Pinus ayacahuite, 21.9%). Nest-site characteristics observed in the study were compared with those reported in the literature 20 yrs ago by Lanning and Shiflett (1983), and important differences were found in the percentages of tree species used. Decline of the Thick-billed Parrot seems to be related to large-scale logging over a wider historical breeding range. Commercial timber harvesting appears to affect nest site availability by leaving few snags and pine trees large enough for parrots to nest in.