Rare Colonial Nesting Discovered in Chimborazo Hillstar Hummingbirds of the Andes

Scientists have discovered that the Chimborazo hillstar hummingbird (Oreotrochilus chimborazo chimborazo), native to the high Andes of Ecuador, exhibits colonial nesting behavior, a rarity among hummingbirds. Typically known for their aggressive territoriality, these hummingbirds have been observed nesting in groups within caves on the Chimborazo volcano, located at altitudes exceeding 3,600m. Researchers documented 23 adult birds and four chicks sharing a single nesting site. This behavior is believed to be an adaptation to the harsh environmental conditions and limited availability of suitable nesting locations in the high Andes. Colonial nesting may offer advantages such as improved information sharing about food sources and potential mates. The initial assumption was that limited nesting sites drove this behavior. However, further research indicated that other factors might contribute to the colonial behavior, as not all available solitary nesting sites were occupied. This suggests that social interaction and cooperation may also play a role in the Chimborazo hillstar's nesting habits. The study, published in *Ornithology* in November 2024, highlights the complex interplay between environmental pressures and social behavior in driving the evolution of this unique nesting strategy.