Seasonal Distribution of the Broad-Tailed Hummingbird (Selasphorus platycercus): A Climatic Approach.

Abstract

The seasonal movements of birds are a phenomenon that has historically been of interest in ecology and biogeography. Despite this, information on how environmental conditions influence migratory behavior and its regulation is still scarce. In this work, we study the Broad-Tailed hummingbird Selasphorus platycercus from an analysis of its populations through longitudinal and latitudinal gradients. We use the frequencies of monthly presence records throughout the annual cycle to identify the breeding areas (corresponding to the summer months), of winter presence (corresponding to the winter months), and annual residence (presence records throughout the year). Subsequently, we use ecological niche models to reconstruct the potential distribution of the summer and winter niches by correlating the climates of each season with the corresponding records. We evaluate the species' climatic preferences between the breeding and winter seasons by transferring the niches from each season to the opposite and by their capacity to inter-predict records between seasons. In addition, we quantify the overlap between the summer and winter niches using a niche similarity analysis. Geographically, we see a clear seasonal turnover pattern along a north-south gradient and records throughout the year (resident populations) in the south-central region of its distribution. We observed a low inter-prediction of records between seasons. Together with the similarity analysis, we suggest that the species is niche-switching (i.e., has different seasonal niches). We identified three seasonal migration patterns among the species' populations: long-distance migratory, short-distance summer migrant, and resident. Our findings suggest that the different migration patterns in this species' populations all over its distribution can be explained through seasonal climatic variations throughout the year.