Nesting biology of Green-and-gold tanager (Tangara schrankii): unique traits for lowland reproductive success?

Abstract

ABSTRACT The Green-and-Gold Tanager (Tangara schrankii) is widely distributed throughout western Amazonia, between 300 and 1650 m, and is a common member of canopy and midstory mixed-species flocks. Although basic nesting aspects are known for this species, detailed information is lacking. This study provides new insights on nesting behaviour and natural history for this species based on 150 nests encountered during eight consecutive nesting seasons in southeastern Peru, Manu National Park. Nests were located between 0.3 and 4.5 m above the ground. The incubation and nestling periods lasted 16 and 13.4 days, respectively. Females conducted 6.2 ± 1.96 off-bouts per day and spent long incubating sessions of 77.4 ± 51.9 min. The length of the incubation bouts and the frequency (trips per day) did not vary across the three stages (early, middle, and late) of the incubation period. The overall daytime nest attentiveness was 65.4% and did not vary along the incubation period. Parents conducted 1.77 ± 1.02 feeding trips per hour. The daily survival rate (0.75) of this species was low compared to other passerines. Our data is consistent with previous T. schrankii nesting descriptions. Nestling period, and feeding rates, however, are much shorter compared to previous reports for other Tangara and related genera. We found that T. schrankii has different nesting strategies, such as locating nests on a variety of substrates, conducting long incubation sessions, fewer off-bouts, and lower feeding rates. These strategies could reduce nest detectability by visual predators, and shorten the nestling period, likely increasing their reproductive success. We suggest that the combination of these nesting traits has allowed T. schrankii to successfully inhabit lowland tropical forests where high predation levels are encountered by nesting birds.