Community modeling reveals the importance of elevation and land cover in shaping migratory bird abundance in the Andes.

The tropical Andes are characterized by extreme topographic and climatic complexity, which has likely contributed to their outstanding current species diversity, composed of many range-restricted species. However, little is known about how the distribution and abundance of highly mobile organisms, like long-distance migratory birds, varies across different land covers, elevations, and climatic conditions within the Andes. We conducted 1,606 distance-sampling point counts across the Colombian Andes, spanning elevations from 253 to 3,708 m, a range of precipitation regimes and representative land covers. We then employed a novel application of a multispecies hierarchical modeling approach to evaluate how elevation, local land cover, aboveground woody biomass, cloud cover, precipitation, and seasonality in precipitation shape the abundance of the migratory land bird community in the Andes. We detected 1,824 individuals of 29 species of migratory land birds, six of which were considered incidental in our study region. We modeled the abundance of the remaining 23 species, while considering observer and time of day effects on detectability. We found that both elevation and land cover had an overriding influence on the abundance of migratory species across the Andes, with strong evidence for a mid-elevation peak in abundance, and species-specific responses to both variables. As a community, migratory birds had the highest mean abundance in shade coffee plantations, secondary forest, and mature forest. Aboveground woody biomass did not affect the abundance of all species as a group, but a few showed strong responses to this variable. Contrary to predictions of a positive correlation between abundance and precipitation, we found no evidence for community-level responses to precipitation, aside for a weak tendency for birds to select areas with intermediate levels of precipitation. This novel use of a multispecies model sheds new light on the mechanisms shaping the winter distribution of migratory birds and highlights the importance of elevation and land cover types over climatic variables in the context of the Colombian Andes.

Racial differences in early adolescent substance use: Child abuse types and family/peer substance use as predictors.

This study examined the associations among child abuse types, family/peer substance use, and adolescent substance use, as well as testing whether these associations vary by race. The sample was derived from the Longitudinal Studies of Child Abuse and Neglect (N = 562). Child sexual abuse, family substance use, and peer substance use were associated with a higher likelihood of adolescent substance use. Sexual abuse was more strongly associated with substance use in Black youth than in White youth. Conversely, greater peer substance use had a stronger association with substance use in White youth than in Black youth.

The type of Setophaga ruficoronata (Kaup 1851) is a hybrid: implications for the taxonomy of Myioborus warblers (Passeriformes: Parulidae).

Hybridization, rapid diversification, and uncertainties surrounding type specimens add complexity to the already intricate taxonomy of high Andean Myioborus warblers of northern South America. In this study, we propose a reassessment of species boundaries within M. ornatus and M. melanocephalus, drawing on comparisons of name-bearing types. We also consider insights from a recent study of a hybrid zone in southern Colombia and northern Ecuador. We present three species delimitation alternatives that offer improved clarity compared to the current taxonomy, and discuss the rationale behind recognizing chrysops and bairdi as distinct species while redefining the species ornatus and melanocephalus, given the available evidence.

Digest: Selection for staggered pollen release as a driver of heteranthery.

Why do some flowers have stamens of different shapes and sizes? Focusing on a group of Neotropical flowering plants, Dellinger et al. tackled this question and found that the evolution of heteranthery, contrary to the predominant view, is not strictly related to pollen-reward pollination and selection for division of labor between stamens. Moreover, they found support for the idea that selection for staggered pollen release might lead to heteranthery.