High survival and low fecundity of a neotropical savanna tanager

Abstract

Demographic factors are fundamental aspects of the population ecology of wild birds. However, they are poorly understood in endemic and threatened birds of the Neotropics. In this study we demonstrate that, as in tropical forest birds, a neotropical bird inhabiting a highly seasonal savanna has high rates of survival and low rates of fecundity. We conducted a 2.5-year mark—resighting study to determine survival, fecundity and population structure for the White-banded Tanager (Neothraupis fasciata) in a 10 547 ha protected area of the Cerrado, central Brazil's savanna. Age-structure appeared to have a stable distribution and sex-ratio was 1.2:1 (male: female). Population and effective population sizes were estimated at 6763 and 3438 birds. Density was estimated at 1.1 individual ha⁻¹ and carrying capacity at 7440 birds. Apparent annual survival rate for adults was 68% and for juveniles 42%. Females bred successfully at 2 years old but males only bred successfully when 3 years old. Average fecundity was estimated at 0.31, being higher for adult females than for subadult females. Our results are more consistent with the pattern of higher survival and lower fecundity observed in tropical birds than the pattern observed in Nearctic birds, even though the Cerrado is a highly seasonal savanna.