Inter‐annual site fidelity and breeding origins of Gray‐cheeked Thrushes in white sand forests of the Peruvian Amazon

Abstract

White sand terra firme forests are unusual ecosystems scattered across Amazonia, covering just 3% of the basin. These forests differ from surrounding forests in their scleromorphic vegetation, low nutrient content, and propensity to harbor endemics. We report the capture of 62 Gray-cheeked Thrushes (Catharus minimus) during a study of the understory avifauna of Amazonian white sand forests near Iquitos, Peru, conducted from 20 June to 8 December 2010–2012. We captured and banded Gray-cheeked Thrushes in white sand (N = 57) and adjacent weathered clay (N = 5) terra firme forests. Sampling for three consecutive days at 19 different sites each year, the inter-annual site fidelity rate of Gray-cheeked Thrushes was 4.8% (N = 3). One bird banded in 2010 was recaptured in 2012. Of the 62 birds, 19.3% (N = 12) were recaptured on subsequent days. All recaptures were in white sand forests. The 19.3% recapture rate of Gray-cheeked Thrushes from sites re-sampled no more than 2 d in a given year suggests the presence of settled and perhaps territorial birds. Using rectrices from 12 Gray-cheeked Thrushes, stable-hydrogen isotope analyses (δ2H) suggest that the geographic breeding or natal origin of all sampled birds was likely northwestern North America. Our results suggest that Gray-cheeked Thrushes exhibit site fidelity and may concentrate in white sand forests—an uncommon and scattered ecosystem type in western Amazonia. However, annual tracking of individual Gray-cheeked Thrushes is needed to fully assess regional patterns of settlement and movement, and the connectivity between breeding and wintering areas.