Hummingbirds are famously the smallest birds in the world, but they are also surprisingly aggressive with each other. Because they are so territorial, you would never think of them as living amicably in colonies. Yet one unusual species in Ecuador is nesting in colonies in the High Andes.
When ornithologist Gustavo Cañas-Valle stumbled upon this fraternization among the Chimborazo Hillstar hummingbirds, he couldn’t believe his eyes.
“It was mind-boggling,” he said in a statement. “Finding them nesting in the same location was amazing. Then I realized that males and non-reproductive females were also roosting in the same space as reproductive females.” That, he said, was even stranger.
Hummingbirds are especially territorial during feeding and nesting. Females typically nest alone, while males ferociously defend their territories, sometimes to the point of fatal confrontations. The discovery of these hummingbirds that are so chummy with each other suggests that they have adapted because of environmental pressures.
Not like penguins
“Hummingbirds are not a species like penguins where you see hundreds of them together,” co-author Juan Bouzat explained. “These are hummingbirds that live in the High Andes, above 10,000 feet, in a very, very harsh environment above the tree line.”
The Chimborazo Hillstar hummingbird. Photo: Shutterstock
Cañas-Valle identified 23 adult birds and four chicks nesting and roosting within a single cave. This particular cave sits over 3,600m above sea level. Nearby vegetation is almost nonexistent, shelter is sparse, and temperatures at that altitude can be frigid despite its location on the equator.
Cañas-Valle and Bouzat wanted to determine whether this sociability was solely due to the harsh conditions and a lack of nesting sites or if it also occurred elsewhere.
The research duo scoured the area, identifying several places where solitary nesting would be possible. While some were in use, a large proportion were not. Instead, 80% of the active nests they found were within colonies. The study suggests that the birds prefer to live together rather than were forced to.
Bird colonies usually exist because the individuals benefit from living together.
“Somehow, they get a benefit…from the social group,” said Bouzat.
Exchanging information?
What that benefit is remains up for debate. Cañas-Valle regularly saw hummingbirds leaving and returning to the cave together. He speculates that the members of the colony may be exchanging information about the location of food and mates.
The situation is so unusual for hummingbirds that some experts question whether the birds are actually showing colonial behavior. Cañas-Valle and Bouzat understand the skepticism. Cañas-Valle joked that it took years just to convince his colleague.
“It took me probably two years for Juan to say, ‘Well, Gustavo, you convinced me. We can call this gathering of nests a colony from now on,’” he said. “I was thinking,’ Finally.’ That was a priceless moment.”
