Breeding season is a hoot!
The breeding season is always an exciting time for us here on the Burrowing Owl Project, and we never know what surprises are in store.
This season at Rancho Jamul Ecological Reserve (RJER), where we completed our second year of translocations, was no exception. It began with long weeks of unusually late rainfall, which flooded several of our artificial burrows and left us wondering whether they would dry out in time to provide a suitable place for our new arrivals to nest.
Luckily, our team is full of expert improvisors, and we added sand to the artificial burrows’ chambers to help provide much needed drainage.
The translocated owls consisted of four pairs and one individual owl from the US-Mexico border fence in Otay Mesa – where they would have been impacted by construction – and two captive-bred second-year owls, hatched at the Bird Breeding Complex at the Safari Park in 2018. These owls were placed in five release enclosures at the translocation site, and after a month of acclimating to their new home, they were released.
And then the excitement really began!
There was an immediate feud between our Cage 1 male, Orange H (named for his colored leg band), and a wild male that had established his territory nearby. Sadly, Orange H lost his mate, Orange A, to the local male and retreated to the hills west of the translocation site. The strapping wild male proceeded to court both Orange A and a second female, who had been translocated to RJER the previous year.
Meanwhile, we were thrilled to find that Blue X, one of the captive-bred females (see Training to Become Wild), had begun nesting with a second-year male who hatched at RJER last year, a case of successful juvenile recruitment!
Together, these first-time parents produced nine eggs. At the following week’s nest check, the field crew discovered that all nine eggs had disappeared. What happened? We examined the photos from the camera trap installed at the burrow’s entrance and found that Orange H was back from the hills, and he and his new mate, Red M, had kicked Blue X and her mate out of their burrow!
Cue the record scratch. Fortunately, the pair quickly renested at a different burrow and ended up fledging six chicks.
When Blue X’s chicks were old enough to receive ID bands, the field crew captured them and were baffled to find three chicks that were already banded in the brood.
We checked their band IDs and found that these three, slightly-older chicks were from a family that had vanished a week prior, and they had traveled 300 meters to foster themselves into Blue X’s family! These adoptees were about seven weeks old, the age at which burrowing owls will often leave their natal burrow, but still tag along with other owls to benefit from safety in numbers and to learn other life skills.
So, not only did Blue X survive the transition to the wild and successfully raise a large family during her first breeding season, but she also fostered three other juveniles on their journey to independence. She is our champion!
The end of the breeding season is always bittersweet, but we will continue to monitor our translocated burrowing owls and their progeny over the fall and winter.
In California, the western burrowing owl is listed as a Species of Special Concern, with habitat loss being one of the biggest threats to their survival. This breeding node at RJER is being established as part of a long-term strategy to save the species in San Diego County. If you would like to help us with our research, you can be a citizen scientist and catalog camera trap images of a family of burrowing owls by visiting our Wildwatch Burrowing Owl Project.
You can learn more about the Burrowing Owl Recovery Program here.