AN UPDATE ON THE BREEDING BIOLOGY AND BIOMETRY OF HAUXWELL’S THRUSH (TURDUS HAUXWELLI) FROM LOWLAND SOUTHWESTERN BRAZILIAN AMAZON

Abstract

The Neotropical region is home to a large number of species of the genus Turdus. While the breeding biology of this genus is well known in general, data are scant for some Amazonian species, including Hauxwell’s Thrush (Turdus hauxwelli). Here, we present new data on the breeding and biometry of T. hauxwelli based on field observations and captures in a fragment of terra firme forest in southwestern Amazonia, Brazil. We monitored six active nests between 2012 and 2014, and collected data on the incubation and nestling phases on five nests. The nests were built at a mean height of 1.9 m (range: 0.53–3.2 m) above the ground. We estimated incubation time as 13–14 days. We monitored the development of 11 nestlings in four nests. The mean weight of the newly-hatched nestlings was 6.56 g (range: 4.3–9.0 g [SD = 2.27]). The constant (K) of the growth rate in the nestlings was 0.43 (range: 0.31–0.51; SE=0.03), with an asymptote of 51.1 g (range: 45.04 - 62.32; SE= 0.31). The daily survival rate of the nests during the incubation phase was 97%. However, the survival rate during the nestling phase was only 12%. Mayfield’s success was 70% during the incubation phase and 21% during the development of the nestlings, whereas apparent success was 75% in the incubation phase and 27% in the nestling phase. We banded and measured 64 adult individuals, 13 juveniles, and four nestlings in 2005 and between 2009 and 2017. Minimum longevity, calculated from the recapture of banded individuals, was 6 years, 3 months and 11 days (or 2298 days after banding). Our results indicate that T. hauxwelli has a breeding season restricted to a few months of the rainy season (November–March), which overlaps with molt.