Effect of food availability and habitat characteristics on the abundance of the torrent duck during the early breeding season in the Central Andes, Argentina.

L. M. ÁLVAREZ, A. A. ASTIÉ, G. O. DEBANDI & E. E. SCHEIBLER

WILSON JOURNAL OF ORNITHOLOGY

WILSON ORNITHOLOGICAL SOC

Año: 2014 vol. 126 p. 525 - 533

1559-4491

The Torrent Duck (Merganetta armata) inhabits rivers and streams across the Andes. This 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 Duck 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 Torrent Ducks present in each stream. We made a PCA to portray the features of each stream. GLM?s was used to estimate which environmental variables were associated to the duck?s 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 Torrent Duck abundance 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.