Nesting at the edge: breeding behavior and nest microclimate of the Glacier Finch (Idiopsar speculifer) on the Quelccaya ice cap, Southeastern Peru

Lazo C.; Diaz R.D.; Díaz A.; Mamani G.C.; Luza-Victorio M.A.; Hardy D.R. · Climate Change Ecology (2026) · DOI: 10.1016/j.ecochg.2025.100106

Resumen

High‐elevation glacierized environments pose extreme nesting challenges for birds, yet the Glacier Finch (Idiopsar speculifer) regularly nests inside ice cavities, but data on active nests and their microclimates remain scarce. We documented these aspects across two breeding seasons (2024–2025) in three sectors on the western side of the Quelccaya Ice Cap, southeastern Peru, above 5300 m asl. We characterized nest structure and composition, parental behavior, and the microclimate within glacier cavities used as nesting sites. We located six nests (four abandoned and two active) and described the structure and composition of three only once they were inactive (one abandoned and the two formerly active). Nests were open-cup structures composed primarily of two high-Andean grass species (Deschampsia ovata and Cinnagrostis nitidula). The active nests were monitored with trail cameras and microclimate sensors. One nest was found in April 2024 and the other in February 2025, the latter representing the earliest breeding record to date, occurring four days before the previously proposed egg-laying period, and the first documented nest built on rock rather than directly on ice. Daily biparental care was observed at one nest, with 8–9 visits per day and no nocturnal activity, whereas the second nest experienced predation by an Andean fox (Lycalopex culpaeus). Glacier cavities acted as thermal buffers, maintaining near-freezing temperatures (∼0 °C), high relative humidity (90–100 %), and low evaporation rates (0.2 kg m⁻² h⁻¹), providing more stable conditions than outside the cavity. These findings enhance understanding of reproduction in extreme glacierized habitats.

Instituciones: Universidad Nacional Agraria La Molina; Universidad Nacional de San Antonio Abad del Cusco