Most hummingbirds are territorial, aggressively challenging competitors over flowers or mates. An ornithologist and birding guide in the Andes Mountains of Ecuador discovered a cave containing 23 adult hummingbirds and four chicks of the Chimborazo hillstar subspecies. After a search of the region, they found six additional colonies. This was the first time hummingbirds had been observed living together, a unique finding published in the journal Ornithology.

These hummingbirds live more than 12,000 feet above sea level on a sparsely vegetated slope, where finding nectar-rich flowers, water and shelter in freezing temperatures and biting winds is challenging. The researchers believe that the harsh environment has led the birds to aggregate for survival. Further research is needed to determine whether the hummingbirds are merely tolerating each other or actively cooperating.