What’s on the menu?
How a state-endangered species has changed its’ diet to survive
When there’s a downturn in the economy, humans often learn to cut corners and stretch resources. The first things to be cut are usually more expensive food items and treats. The animal kingdom is similar in how it adapts; when a traditional food item is no longer available, many species will make do with an alternative.
Ferruginous hawks. for instance, once dined almost exclusively on ground squirrels and jackrabbits. Over the years, much of the hawks’ shrubsteppe habitat has been lost to development and conversion to agricultural uses. The prey species they depended on disappeared with the habitat. As a result, these birds are now listed as endangered in Washington but have managed to survive with some tweaks to their diet.
Washington Department of Fish and Wildlife (WDFW) scientists have been studying ferruginous hawks in southeast Washington for several years. In our last blog about the study, Take two: the continued travels of hawk 264292, we wrote about how raptor research scientist Jim Watson and assistant district wildlife biologist Mark Vekasy in 2024 put up game cameras focused on the nests of ferruginous hawk pairs. Due to technical difficulties, the game cameras didn’t generate much usable footage.
This spring, Woodland Park Zoo’s Living Northwest Conservation Program provided new cameras and transmitters for the project.
As hoped, the new cameras are providing an up-close look at what’s on the menu at three platform nests across Walla Walla County.
“We’re seeing about what we expected but couldn’t document last year,” said Vekasy about the photos the cameras have provided so far. “Although we’re still seeing ferruginous hawks consume pocket gophers, later in the nest season we’re seeing snakes brought to the nest by the adult hawks to feed the young.”
According to nest photos, there are two snake species commonly served to young hawks in roughly equal numbers- Western racers and gopher snakes.
Watson and Vekasy have also observed some fledgling meadowlarks being fed to nestlings. You can see a meadowlark foot in the photo below of the north nest if you look closely.
The chicks in the nest farthest east are the oldest, at two months old as of late June. The north nestlings hatched the day after, and the ones in the southern-most nest three days later. In early June, the northern nest chicks were big enough to swallow some prey whole, but the adult female continued to feed them. In the following photos, you can see pocket gophers and deer mice she brought to the nest.
“The nestlings in the south nest seem to be getting less prey items than the other two sites,” Watson said. “And if you compare the ages directly, they appear thinner than the nestlings from the other sites when they were the same age.”
This difference in growth can also be seen when taking a close look at the development of the hawk’s feathers. Wing and tail feathers can show very slight, and sometimes more pronounced, “fault bars”- narrow, translucent bands that appear across the feather indicating periods of stress, or in this case, malnutrition, during feather growth. Less prey delivered to this nest is probably a function of lower prey availability rather than poor hunting abilities of the adult hawks.
The nestlings will soon be hunting for themselves. Between 38 and 50 days after hatching (usually between late May and late July) is the approximate time when chicks fledge, or leave, the nest. As they approach a month old, they start testing out their wings, stretching and flapping them, like the one in the photo below. Two of the young, one from the north and one from east nest, so far have fledged. The east nest bird has been out of the nest successfully for over a week now but returns to visit siblings regularly.
While the birds that haven’t fledged yet may not be able to fly, all of the nestlings can glide fairly well at this stage. This is important if they need to escape from the nest in the event a predator, such as a great-horned owl, attacks. In a matter of days though, they will all likely have fledged, leaving the hawk parents as literal empty nesters.
If that sounds nice to you as a human parent, be aware that it only lasts for the summer. Ferruginous hawks typically stay with the same mate throughout their adult lives and will often return to the same nest from the year before to produce more young next spring.
You can find more information on ferruginous hawks on WDFW’s website.
