Nest survival of the threatened Campo Miner Geositta poeciloptera: a tropical cavity-nesting grassland bird

Nest survival is a key step in the reproductive biology of birds and is essential for understanding the strategies used to improve the chances of nest success. Here we studied the main factors driving nesting success of the Campo Miner Geositta poeciloptera (Scleruridae), a threatened Neotropical grassland bird that nests in cavities, usually along steep soil banks. We calculated the apparent success and modeled daily nest survival rates (DSR) based on 86 nests monitored to investigate the effects of nest-related covariates on the nest survival. In the DSR modeling, we looked at the effects of reproductive phase (incubation and nestling periods), breeding seasons (years), temporal-trends (linear and quadratic) rainfall, and nest’s individual covariates (height, distance from the top of the cavity to the top of the bank, cavity depth and cavity entrance area). The overall apparent nest success was 58% and estimates based on DSRs were ~45%. Nest phase, cavity entrance area, nest height, and a linear time trend were the main factors influencing DSRs. The survival during incubation was lower (~54%) than during the nestling period (~83%), and both phases showed higher values in the beginning of the breeding season. Predation was the main driver of nest failure (23.3%, N = 20), followed by nest abandonment (10.5%, N = 9) and nest usurpation (7%, N = 6). Our results allow us to better understand and conserve this threatened species and also sheds light in the reproductive ecology of a whole family endemic to the Neotropics.