Complex breeding phenological shifts of neotropical birds across space and time

Climate change is altering breeding phenology patterns in different ways across regions, periods and species. We examined spatial and temporal variation in the breeding phenology of four Neotropical birds, specifically testing whether the magnitude of phenological shifts increases with distance from the equator, as previously reported for Northern Hemisphere species. We used data from 1310 clutches from Pitangus sulphuratus, Zonotrichia capensis, Tyrannus savana and Troglodytes aedon, spanning 1901-2020 and latitudes 32°N to -54°S. Breeding dates were analysed in relation to time, latitude and climatic variables through Bayesian linear models. Species showed very contrasting responses. Temporal patterns differed among species: Ty. savana and Tr. aedon delayed breeding over time, P. sulphuratus advanced and Z. capensis showed no temporal effect. Latitude influenced breeding phenology in Z. capensis, and year-latitude interactions indicated spatial variation in temporal changes for Ty. savana and Tr. aedon. Although all species analysed exhibited latitudinal structure in breeding phenology, the magnitude and direction of temporal changes differ among species, with no evidence that phenological shifts become stronger at higher latitudes farther from the equator, and that the Northern and Southern Hemispheres show different patterns.