Nest survival rates of Red‐crested Cardinals increase with nest age in south‐temperate forests of Argentina

ABSTRACT The main cause of nest mortality for most bird species is predation and nest survival rates often vary in relation to time‐specific variables. Few investigators have examined time‐specific patterns of nest survival in Neotropical birds, and most such studies have focused on tropical and subtropical species. To better understand age‐related patterns of nest survival, we studied nest survival of Red‐crested Cardinals (Paroaria coronata, Thraupidae) in a south‐temperate forest in Argentina. We modeled daily nest survival rates (DSR) using program MARK. We examined the relationship between nest age and nest survival rate, controlling for the effects of physical characteristics of nest sites and progression of the breeding season. We monitored 367 nests for a total of 4018 exposure days. We found that DSR increased with nest age and was higher in small isolated patches than in large continuous patches of forests. The increase of DSR with nest age could be a consequence of more vulnerable nests being predated early in the nesting cycle or a result of parents defending nests more vigorously as nestlings age because of their increasing reproductive value. Open areas of grassland that surrounded the small isolated patches of forests in our study may have been a barrier to predator movements, possibly explaining the lower predation rates. Nest survival rates in our study were lower than those reported for tropical or Nearctic temperate birds, but similar to those reported in other studies of Neotropical temperate birds. Reasons for the low nest survival rates of Neotropical temperate birds remain unclear, and additional studies of predator communities are needed to help elucidate this topic.