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 individuals in the stream with the lowest disturbance (Arroyo Grande) and four individuals in the most highly disturbed stream (Río Blanco). Variation in abundance of Torrent Ducks was better explained by a higher density of Notoperla, Plecoptera (an aquatic insect associated with clean waters) and to a lesser extent by flow rate.
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