Effect of food availability and habitat characteristics on the abundance of Torrent Ducks during the early breeding season in the central Andes, Argentina

ABSTRACT Torrent Ducks (Merganetta armata) inhabit rivers and streams across the Andes. The species feeds mainly on aquatic invertebrates and occurs in rivers with high flow rate, large emergent rocks, and low anthropogenic disturbance. The objective of this work was to study the effect of food availability and environmental variables on the abundance of Torrent Ducks in two streams with different levels of anthropic disturbance and diverse environmental conditions. To describe each stream, we recorded density and richness of benthic macroinvertebrates and physical-chemical variables, and characterized the stream habitats. We also censused the number of Torrent Ducks present in each stream. We prepared a principal component analysis to portray features of each stream. Generalized linear models were used to estimate which environmental variables were associated with the ducks' abundance and to explore variations in biotic variables between streams and between sections within each stream. We recorded 40 ind...