Nesting of eight species of Tyrannidae in the Reserve of Ñacuñán, Mendoza, Argentina

Abstract

The breeding biology of eight species of Tyrannidae in the Reserve of Ñacuñán (centralwestern Argentina) is studied. The reserve is located near the western or southern limit of the distribution range of these bird species in Argentina. As a whole, laying period spanned from mid October to mid January, although breeding chronology varied depending on the species. Most clutches of Stigmatura budytoides started around mid spring, while egg laying in Griseotyrannus aurantioatrocristatus began mainly in early summer. Breeding activity differed in some species during the four years of study, generally being more intense in the wet 1997-1998 breeding season. All species used algarrobo or chañar trees as nesting sites, although some of them also used tall shrubs. Griseotyrannus aurantioatrocristatus and Stigmatura budytoides nested in chañar trees somewhat larger than those available in the habitat. However, differences in chañar features and nest placement related to nest fate (i.e., failed or successful) were not found. Clutch size in Stigmatura budytoides was always two eggs and in Myiarchus tyrannulus was five eggs, although in general was 2–3 eggs for the remainder species. Eggs were laid on alternate days in four species; only Tyrannus savana laid one egg daily. The duration of incubation period ranged from 12.8 to 16.0 days and of nestling period from 12.0 to 15.0 days depending on the species. Data on fledging productivity and chick characteristics are also shown.