Breeding Biology of Barred Forest-Falcons (Micrastur ruficollis) in Northeastern Guatemala

Abstract

Little is known about the reproductive biology of most Neotropical raptors (Thiollay 1985). One particularly little-known genus is Micrastur, the forestfalcons, which comprise a group of six species of small to medium-sized falconids that inhabit tropical forests from central Mexico to northern Argentina (Brown and Amadon 1968, del Hoyo et al. 1994). Forest-falcons are characterized by a long tail, short wings, and a slight facial ruff (Brown and Amadon 1968, del Hoyo et al. 1994), which appear to be adaptations to tropical forest environments. Here, we report new information on the breeding biology of the Barred Forest-Falcon (M. ruficollis) in a relatively undisturbed lowland tropical forest in Guatemala. Study area and methods.-We studied Barred ForestFalcons in Tikal National Park, northeastern Guatemala (17?13'N, 89?36'W), from 1988 to 1996. Vegetation in the 576-km2 park is semideciduous tropical forest with rolling hills ranging from 200 to 400 m elevation. Tikal has a pronounced wet and dry season. Rains usually start in May or early June and decrease by December. During our study, monthly precipitation ranged from 1 mm in March 1991 to 302 mm in September 1989. Mean annual rainfall was 1,309 mm from 1988 to 1995 (pers. obs.), and mean monthly temperatures ranged from 15?C in January to 35?C in May from 1989 to 1995. We searched the forest daily from March through July to document activity of potential breeding pairs. Forest-falcons are most active in the morning and evening, and we concentrated our searches to these hours, usually beginning between first light and 0900. We followed pairs by sight and sound until a nest was confirmed by behavior of the birds. When possible, we climbed nest trees to observe eggs or young in cavities, sometimes with the aid of a flashlight. Nest observations totaled more than 1,800 h, most of which occurred during the breeding seasons of 1989 through 1992, with incidental observations from 1993 to 1995 and for four weeks in 1996. For each nest, we determined laying date, clutch size, hatching success (by periodic checks of nest cav-