No abstract

The Eastern Kingbird (Tyrannus tyrannus) is an American boreal migratory bird that arrives in the lowlands of the eastern slope of the Andes in South America during its non-breeding season. However, there are some historical migratory records of this species on the western slope of the Andes, but the information is poor and scattered. Here we present a comprehensive analysis of the migratory patterns of the Eastern Kingbird, giving more attention to the migratory route throughout the arid ecosystems in western Peru and Chile. We modeled monthly density heatmaps and evaluated the annual migratory movements of the bird in the southern hemisphere using the records available in the Global Biodiversity Information Facility repository. We found that the species frequents the arid ecosystems of western South America often than previously published. We recognized that the species follows the same pattern of migration in both the western and eastern humid areas South America; nevertheless, we identified that the species is present year-round in northern South America, mainly in Colombia, with some records during the breeding season (April-August) in Peru and Chile. We strongly recommend the use of citizen science datasets to elucidate the migratory patterns of other boreal migratory bird species.

Background Among the New World vultures, the Andean condor is considered one of the most culturally and ecologically important species. However, their populations are declining over their entire distributional range. In response, conservation strategies have been implemented in many countries to reverse the increasing extinction risk of this species. The initiatives rely on extensive population surveys to gather basic information necessary to implement policies and to intervene efficiently. Still, there is a need to standardize the surveys based on seasonality and suitable environmental conditions throughout the species distribution. Here, we provide the first assessment of how daily temperature, rainfall, and seasonality influence surveys of Andean condors on a communal roost in the central Peruvian Andes. Methods Using an autoregressive generalized linear model, we associated environmental variables with visual surveys of adult and young condors at three different times of the day and three times a week between June 2014 and March 2015. Results We found that both adults and young Andean condors showed a threefold reduction in the use of the communal roost after the beginning of the rainy season. Colder and drier days (dry season) are preferable for surveying, as we expect the total number of condors using communal roosts to reduce under rainy (rainfall = −0.53 ± 0.16) and warmer days (temperature = −0.04 ± 0.02) days. Therefore, the significant variation in the use of roosts across seasons and hours should be carefully accounted for in national surveys, at the risk of undermining the full potential of the communal roost surveys. Moreover, we also found a strong bias towards immatures (about 76%) in the adult:immature ratio and a remarkable absence of Andean condors during the wet season. These results suggest that the species might be using other unknown communal roosts hierarchically. Such results provide key information for selecting priority areas for conservation and selecting the best time to survey this species in the tropical Andes. Finally, it may open a fruitful avenue for further research on the protection of the Andean condor.