Red-crowned cranes let their fellows stay to raise their children

In India, the red-crowned crane, a red-crowned crane as tall as an adult, is famous for its habit of living in pairs. However, KS Gopi Sundar, a scientist with the Indian Union for Conservation of Nature, has found that sometimes pairs of cranes allow a third individual to join. He describes this behavior in the March issue of the journal Ecology. According to research, it could help cranes raise their young in difficult conditions. The third bird can act as a domestic helper.

Sundar observed the first trio of red-crowned cranes in 1999. He followed them for the next 16 years. Beginning in 2011, he also trained field assistants (usually local farmers) to monitor cranes. After collecting information over the course of 2020, Sundar and Swati Kittur, a colleague from the same association, mined the database to find triplets. Observers detected 193 groups in more than 11,500 observations. Sundar concludes this behavior is very rare. Some groups consist of one male and two females or vice versa.

Suhridam Roy, a graduate student at the association, approached four of the trio of cranes and recorded their cries. Each group has its own song. The data did not reveal how many cubs the trio had raised or how long they stayed together. But 16 years of observing the first trio of cranes provide some clues. These cranes live in harsh environments. The small amount of marsh is likely to make raising young difficult for a common pair of cranes.

However, in group three, the results were better. Each year, one adult in the triptych (usually a female) disappears while the other two nest and lay eggs. According to Sundar, only two out of three individuals mate each season. When the chicks are about a month old, the absent female will reappear and help feed the young. Three cranes work together to raise a baby bird almost every year.

The research team believes that the habit of living in groups of 3 individuals is a way to adapt to difficult conditions. Co-parenting is quite common in the animal world. Monkeys, mongooses, spiders, insects, birds and fish also cooperate to reproduce. Sundar is planning to use genetics to study birds in addition to being related to the other two birds in the group.

An Khang (According to New York Times)