Intraspecific variation in exploratory behavior and elevational affinity in a widely distributed songbird

Abstract

Populations of the same species can vary substantially in their behavioral and morphometric traits when they are subject to different environmental pressures, which may lead to the development of different adaptive strategies. We quantified variation in exploratory behavior and morphometric traits among two rufous-collared sparrow populations that occur at low and high elevations in central Chile. Moreover, we used census and δH values of feather and blood to evaluate migration. We found that individual sparrows inhabiting high elevations were larger and showed more intense exploratory behavior in comparison with those that were captured at lower elevation. Moreover, we observed a steady decline in sparrow abundance during the winter and similar δH values for blood collected in the winter and summer at this site, which were significantly lower than blood δH values observed at low elevation. This pattern suggests that individuals do not move long distances during winter, and likely they remain at similar elevations in refuge habitats. As predicted, our results support the existent of different adaptive strategies among populations of the same species, and suggest that the combination of behavioral, morphometric, and stable isotope data is a novel and robust integrative approach to assess differences in adaptation across environmental gradients.

Evidence for intraspecific phenotypic variation in songbirds along elevation gradients in central Europe

“…Interestingly, our results do not provide much support for Bergmann’s Rule, which predicts shorter wings and larger bodies in colder (and therefore higher elevation) environments (as shown by Meiri & Dayan 2003, Laiolo & Rolando 2008, Poblete et al 2018). The combined‐species model suggested a general decrease in body mass with elevation, although at the individual species level (Table S3) there was a single species, Willow Tit, that showed an increase in body mass.…”

“…Species with high variability in traits may more readily adapt to environmental changes (Lehikoinen et al 2018). Phenotypic variation within species is shaped by the spatial and temporal differences of the habitats in which different populations live and includes differences in morphological traits such as wing length (Poblete et al 2018). Studies of phenotypic variation in relation to the environment are important, as they may reveal fundamental drivers of variation within and between species.…”

“…a higher body mass) with relatively shorter extremities, e.g. legs and wings, at high elevations (Meiri & Dayan 2003, Laiolo & Rolando 2008, Poblete et al 2018). This may arise through selection for larger animals that have a lower surface area to volume ratio than smaller animals, so they radiate less body heat per unit of mass, in agreement with Bergmann’s Rule.…”

Differences in circulating corticosterone levels associated with elevation of breeding sites in Rufous-collared Sparrows Zonotrichia capensis

“…In contrast, at high elevations, the breeding season is shorter, probably with no more than two clutches per year (Wingfield et al 1995). Despite harsh environmental conditions during the winter at high elevations (Di Castri and Hajek 1976), this species does not migrate downslope and instead remains at the same elevations in refuge habitats during the winter (Poblete et al 2018).…”

“…Rufous-collared Sparrows (Zonotrichia capensis), a common passerine species in Central Chile, present populations which breed across this gradient from sea level to > 4000 m.a.s.l. Individuals at low elevations are resident year-round (Poblete et al 2018), and present long breeding seasons, possibly producing multiple clutches per year (Couve et al 2016). In contrast, at high elevations, the breeding season is shorter, probably with no more than two clutches per year (Wingfield et al 1995).…”