Hatching, Raising & Releasing: Inside the California Raptor Center Nursery
By Julia Moules
In the sprawling farmland of Yolo County, field workers often come into contact with wildlife, including the nests of wild birds and their eggs or hatchlings. This represents a dangerous crossroads for young birds, but a collection of local volunteers led by one full-time staffer is dedicated to helping ensure survival.
The California Raptor Center, which is part of the UC Davis One Health Institute, accepts all discovered eggs and hatchlings from anywhere within driving distance of Davis.
From the time an egg arrives at the nursery until a hatched bird is released back into the wild, here's what the process looks like:
It's important that eggs are brought to the California Raptor Center as soon as they're found. To stay viable, eggs must be kept around 99.8 degrees Fahrenheit. When they reach the nursery, they're kept in incubators at this well-regulated temperature until they're hatched.
When the center receives an egg, the primary goal is to return it to its natural environment, but if the original nest has been destroyed or is in harm's way – like on a farm – that's not an option. If that's the case, researchers try to place the egg in the nest of another bird of the same species. But they don't want to jeopardize one bird to save another, so they must first determine if the nest can accommodate an extra mouth to feed. If it cannot, the egg will likely remain in the nursery.
Most eggs brought to the California Raptor Center are Northern Harriers that are found in rice and wheat fields. They also tend to receive a few Great Horned Owls and barn owls each year. Breeding season for these birds starts around April and lasts until August.
The birds in the California Raptor Center nursery are cared for by a rotation of volunteers.
One reason researchers try to immediately return eggs and hatchlings to their natural environment is to avoid having birds imprint on humans or other species. Imprinting can happen on sound or sight, and it's irreversible. Birds that imprint on humans can't survive in the wild, which means they can't be released.
That's why nursery caretakers use puppets and wear masks when feeding and handling the hatchlings. (Video above)
"Imprinted birds can be decent parents, but don't have the instinct to breed," said California Raptor Center Manager Bret Stedman. He added that the imprinted birds that live at the center can't instinctually care for hatchlings, but they can play a surrogate role by teaching young birds how to feed while allowing them to imprint on their own species.
About seven-to-ten days after hatching, the temperature is lowered from 98 degrees to the mid-to-upper 80s. After feathering, the bird can be cared for at room temperature.
Newborn hatchlings are fed five times a day using the puppets. After a week or so, feeding is reduced to twice a day. After three weeks, the birds are allowed to be outside. That's when they're placed in front of other birds of their own species so they can naturally imprint and begin to learn behavior skills.
Some birds are more susceptible to human imprinting than others. Gray owls, for example, are more likely to imprint than barn owls.
One popular technique for releasing nursery-raised birds into the wild is "hacking."
Hack boxes allow the bird to adapt to the wild and acquire natural instincts with minimal danger. Most birds are ready to be released sometime between 30 to 90 days of life, but that varies by species.
Hack boxes allow birds to learn to fly and adapt to the wild without completely cutting them off from their caretakers. Food is placed on the boxes for several weeks as the bird learns to hunt. Over time, the birds will acquire their survival instincts and will no longer be dependent on the food left at the hack boxes.
The California Raptor Center's hack boxes are located in Davis and at locations near surrounding towns such as Woodland and Placerville.
Here's how it works: Birds are placed in the hack box at least a week before they begin to fly. A bird that already knows how to fly would likely not return to the box, which is why it's important to start early.
Food is placed on the box every day, which gives the bird an opportunity to learn to hunt without being completely cut off from its food source. Eventually, the bird will be able to sustain entirely on its own hunting.
This technique is used for a variety of birds at the California Raptor Center, but not with barn owls, which are released locally in the Davis area. Barn owls can feed on their own after just 15 days and are ready for release without the need for a hack box after just 28.