The Scarlet Macaw (Ara macao) is a widely distributed parrot that has suffered reduced abundance and increased isolation in Mesoamerican populations. Understanding environmental and temporal factors that influence nest survival may assist efforts to increase annual recruitment for this species, improving population viability. We examined nest survival of Scarlet Macaws in the Maya Biosphere Reserve of Guatemala and Chiquibul Forest of Belize in 2010. Our results suggest that connecting tree canopies have the greatest negative influence on daily nest survival, reducing the probability of a nest surviving the entire nesting period from 0.89 to 0.42. This is likely due to facilitating nest access to predators. Nine of 20 nests in Belize, but no nests in Guatemala, were poached. The majority of poached nests were located in close proximity to a reservoir, which may facilitate access to nests. Based on previous estimates of nest survival required for this population to remain stable, our 2010 data suggest that the population in Guatemala could be growing, but that poaching has reduced nest survival below the threshold for population stability in Belize. Reducing habitat loss in Guatemala and nest poaching in Belize would most benefit this historically connected population.