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Hummingbirds Found Nesting Together in Groups in Surprising First

New findings imply that Chimborazo hillstar hummingbirds are changing their solitary nature.
ByCaLea Johnson|
The Chimborazo hillstar is native to the Andes of Ecuador and southern Colombia.
The Chimborazo hillstar is native to the Andes of Ecuador and southern Colombia. | ©Juan Carlos Vindas/GettyImages

Hummingbirds aren’t just the smallest members of the avian class. They are also known for being largely solitary, and some aggressive species will even chase and stab each other when competing for food or mates. Researchers were, therefore, shocked to discover dozens of hummingbirds nesting together in a “hive” in an Ecuadorian cave.

According to The New York Times, an ornithologist named Gustavo Cañas-Valle came across the rare sight in Ecuador’s High Andes. He noted 23 adults and four chicks of the hummingbird species Oreotrochilus chimborazo, or the Chimborazo hillstar. His study in the journal Ornithology marks what is likely the first documentation of hummingbirds nesting and roosting together in the same area. Such practices aren’t even common among the most social bird species. 

What explains the sudden change in behavior? Cañas-Valle and Juan Luis Bouzat, an evolutionary geneticist at Bowling Green State University in Ohio and co-author of the study, initially believed the environment was the main culprit. More specifically, the experts thought the freezing temperatures at more than 12,000 feet above sea level might have encouraged the birds to get cozy. The scarcity of water, flower nectar, and shelter were also suspected causes.

Upon exploring the region further, however, Cañas-Valle and Bouzat found this wasn’t the case. They identified six more instances of hummingbirds roosting and nesting together. Only 45 percent of the concrete drainage pipes they surveyed—which offered more privacy to the birds and could fit one or two nests—were used by nesting females, which was lower than the number projected by computer simulations.

Hummingbird hives, meanwhile, were more common than the computer predicted. Eighty-two percent of the 74 documented nests were part of groups, implying that the hummingbirds chose to live amongst others instead of alone. Bouzat estimates that the environment might have initiated the change in hummingbird behavior, causing them to adopt more social lifestyles that persisted.  

Some scientists are skeptical. Charles Brown, a behavioral ecologist at the University of Tulsa, doesn’t believe that the birds in the study should be considered colonial. According to The New York Times, he argues that colonial animals show partnerships that involve working together to help each other, such as hunting for food, and there’s no proof of such behaviors amongst the hummingbirds. But Cañas-Valle said the birds weren’t ignoring each other; he even noticed them traveling to and from the cave together, implying some group collaboration. Nonetheless, Cañas-Valle and Bouzat admit that further research must be done to determine if the hummingbirds see themselves as a community.

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