A unique phenomenon was recently discovered in a nesting box on the Golan Heights - an adult barn owl with a clutch of five chicks and a common kestrel nestling, a bird of prey belonging to the falcon family, that was "adopted" by them.
Uriah Sadeh, the Golan Heights regional coordinator for the Israeli Barn Owl Project – an initiative looking to utilize the bird of prey as a form of natural pest control in agriculture, conducted his annual inspection of the owl nesting boxes and was taken aback by what he saw. He carefully examined the physical condition of the nestlings, documented the event and continued to closely monitor the unique case.
On a subsequent visit a few days later, Itai Bloch, the national and scientific coordinator of the project, joined the inspection of the three surviving nestlings, including the falcon. According to him, the young kestrel seems to be developing well despite being "adopted" by the barn owl family.
"Cross-species adoption is a rare phenomenon in the natural world. While we are familiar with instances like cuckoos laying their eggs in the nests of other bird species, such occurrences are exceptions rather than the norm. Interspecific adoption of a kestrel by a barn owl hadn’t been observed before even by the project’s veterans," said Bloch.
"Most likely, a pair of kestrels found an empty box and began nesting in it. After the female kestrel laid an egg in the nest, a pair of barn owls arrived and drove the kestrels out of the nesting box. The barn owl continued to incubate the kestrel egg alongside its own eggs, and even after the kestrel hatched, it continued to care for it as if it were her own."
The Society for the Protection of Nature in Israel noted that kestrels and barn owls occupy similar ecological niches. While kestrels are active during the day and barn owls are active at night, both species regularly feed in agricultural areas, primarily in field crops.
"We often encounter kestrels adopting nesting boxes intended for barn owls," the environmental group told Ynet. "They compete for available nesting boxes, and when there is a shortage of vacant ones, barn owls and kestrels may vie for the chance to nest in a nesting box. In such cases, barn owls have a physical advantage over kestrels, and most of the time, they emerge as the winners in the fight."
Prof. Yossi Leshem, an ornithologist and professor at Tel Aviv University's School of Zoology who heads the Israeli Barn Owl Project, said, "Every year we monitor thousands of nesting boxes throughout the country and track the nesting using online cameras. Occasionally, we come across young barn owls entering nesting boxes belonging to another family, but this is the first time in the project’s 40 years that we encounter such a remarkable case, where a barn owl is raising a common kestrel nestling."
Prof. Leshem, who initiated the project, added, "The young kestrel had to adapt to its adoptive family. Night meals, which are almost exclusively composed of mice, are typical for barn owls. In addition, barn owls tend to swallow their prey whole, while kestrels chop the prey into pieces and eat smaller chunks. However, nature has its own rules, and the young kestrel finds a way to cope. Moreover, this story raises intriguing questions about the behavior of the kestrel. We hope that just as it has found a way to survive until now, it will continue to find ways to survive and thrive."