Breeding seasonality in Charadriiformes on the Andean Altiplano is influenced by rain and possibly flood risk

Abstract The Andean Altiplano in South America represents a remarkable mountain ecosystem with unique wildlife. However, knowledge of breeding ecology for birds inhabiting Andean Altiplano is scarce, relying mostly on anecdotal records, and drivers of breeding phenology remain unexplored. Here, we combined records of community‐driven naturalistic databases, published literature, and our own field observations to provide an up‐to‐date account on timing of 354 breeding attempts for 11 species of ground‐nesting Charadriiformes breeding above 3000 m on the Andean Altiplano‐Puna plateau in Peru, Bolivia, Chile, and Argentina, for the period 1964–2023. We recorded clear annual seasonality for Andean shorebirds and gulls, with most individuals initiating breeding between July and December. Birds started breeding earlier when closer to the Equator, and starting date was delayed with increasing elevation. Climatic variation in precipitations and mean temperature during chick care and incubation periods best explained breeding timing. This result suggested that local birds likely use environmental information to predict favorable conditions to incubate and rear their chicks. Increased rainfall and temperature were associated with advanced breeding start, while number of rainy days was associated with delayed initiation of breeding. Our field observations provided additional evidence that within the same locations, rainfall could influence differently various shorebird species. Species nesting on impermeable soils interrupted courtship activities with increasing rains, while species courting further from water level maintained or increased courtship activity with increasing rainfall. These local observations were additionally supported by community science data. Our study provides the first comprehensive exploration on breeding phenology of Andean shorebirds. It indicates more complex patterns than previously published, highlighting that climatic variation and local nesting environment can affect phenology of tropical ground‐nesting birds.