Wildlife Wednesday Free Event: Tracking Cooper’s Hawk Survival

By Ben Neary/NMWF

A team of federal biologists has published an award-winning paper examining the causes of death of Cooper’s hawks in Albuquerque. 

Team member Kristin Madden, a biologist with the U.S. Fish and Wildlife Service, will give a free presentation in Albuquerque on Oct. 14 to discuss the study. She’s the featured speaker for the New Mexico Wildlife Federation’s “Wildlife Wednesday” event.

Madden, chief of the USFWS’s Migratory Bird Program for the Southwest Region, has served as deputy regional director for the agency for the past year and a half, overseeing several states.

Madden and Brian Milsap, former National Raptor coordinator for the USFWS, and wildlife biologist Robert Murphy analyzed the causes of death for Cooper’s hawks in Albuquerque over a 10-year span. Their published, peer-reviewed study was recently awarded Best Paper in the Journal of Raptor Research.  

Urban sprawl forces out many wild animals but a select few can thrive in developed areas. The Cooper’s hawk is one of the survivors that adapts well to living close to people.

Walk along any irrigation channel in Albuquerque and sooner or later, you’ll see a Cooper’s hawk. They often perch in trees, scanning for prey.

Unlike raptors that evolved to hunt in more open country, Cooper’s hawks have relatively short wings and long tails, essential for quick maneuvering after their prey in overgrown, crowded areas, Madden said.

“One cool thing about Coopers is their size,” Madden said. “They can pretty easily find places to nest and they can maneuver more easily. These are birds that evolved in woodlands, so they can get in and out of bushes, they can get around buildings, they’re amazingly agile.”

Madden said the Cooper’s hawk’s main diet is other birds, especially pigeons and doves. “Really, their diet and the availability of those types of birds, and water, really has made this a wonderful place for Cooper’s hawks,” she said of Albuquerque.

But Albuquerque and other densely populated areas also carry hazards for Cooper’s hawks.

Madden and her colleagues captured 158 female Cooper’s hawks around Albuquerque between 2011–2021 and fitted them with transmitters that allowed them to track the birds. They recovered birds that died during the study and assessed what killed them.

They concluded that most of the deaths were related to human factors, including birds flying into vehicles or flying into reflecting windows on buildings. They also found that humans intentionally killed some of them.

“Collisions are our biggest threat in the urban environment,” Madden said. She said people can put decals or blinds on their windows to make them more visible to birds.

“When Cooper’s hawks are chasing prey, they are not paying attention to whatever it is that’s around them,” Madden said. “If the dove thinks that they can get through your window, because of a reflection, they will both hit your window.”

During the mortality study, Madden and the team sent several of the female Cooper’s hawks that they found dead to the National Wildlife Health Laboratory for testing.

Every hawk tested in the study showed some level of rodenticide that’s commonly used for pigeons and doves, Madden said. She said gas stations will often put the material on their roofs to control pigeons and said some homeowners use it as well.

Madden said she would encourage Albuquerque residents not to use rodenticides.

“Not using rodenticides is really good. People think, ‘we’ve got rodents, we need to use rodenticides,’” Madden said. “But if you’ve got raptors, you really don’ t need to use the rodenticides as much. 

To track the Cooper’s hawks, Madden and her colleagues trapped female birds and fitted them with tiny transmitters. They only used females because they’re larger than the male birds and were strong enough to carry the transmitters, she said.

To capture adult Cooper’s hawks, Madden said the research team would commonly tether a great horned owl near an observed hawk nest. When the hawks swooped in to try to harry the owl away, the hawks became tangled in thin netting strung around the owl.

The researchers tried using model owls but found the Cooper’s hawks weren’t easily fooled. The team is now on its second live owl.

“It’s a nonreleasable bird that came from a rehabilitator,” Madden said of the owl, which she said is named Royal. “Those birds have to get a job or they need to be euthanized.”

Royal proved to be calm enough and did the trapping job well enough that researchers permitted him specifically for that particular job.

When Royal’s not on the job helping to trap Cooper’s hawks, Madden said he also serves as a foster parent for wildlife rescue when orphan owl chicks are brought in. “Some of them will go to Royal’s caretaker, and he’ll serve as the foster dad for orphaned youngsters, which is kind of cool,” she said.

The trapping typically heats up in March, when male Cooper’s hawks get active in the mating season, Madden said. She said the team uses a different method to capture the smaller male birds and Cooper’s hawk chicks, using a special snare trap shaped like a sombrero that lures the hawks in to try to catch captive sparrows or starlings.

“That’s what we use early in the season, before the adults have kids that they’re looking to protect,” Madden said of the snare system. “And then we use that again later in the season for the kids.”

Although the research paper into Cooper’s hawk mortality has been published, Madden said work continues that requires ongoing trapping. She said she and Milsap, now a professor at New Mexico State University, are continuing to research to explore the difference in the size of the typical female and male Cooper’s hawks in the Albuquerque area. She said the differential between the larger females and the smaller males is greater in their study area than elsewhere for the species.

“We’ve got one of the largest size differentials in the county,” Madden said. “Females can be anywhere from one and a half to more than twice the size of males.”

“They occupy different niches and they take different prey,” Madden said of the Cooper’s hawks in Albuquerque compared to elsewhere. “So it could be something like that, it could be an energy saving thing in such an arid environment. Who knows, but it’s interesting.”

“For now, our strictly urban population is doing just fine,” Madden said of the Cooper’s hawks in Albuquerque. She said the population has consistently grown over the course of the study and said they’re now a source population for other areas. 

The Rio Grande through Albuquerque has run dry this summer, the latest in a string of increasingly hot, dry years. Nonetheless, Madden said the Cooper’s hawks are still doing well. 

“The fortunate thing for these birds is that people provide water and feed birds. And the pigeon population doesn't seem to be going down at all,” Madden said. “I don’t know about the birds that nest in the Bosque, certain with the lack of water and lack of prey but the fires, I would think, have almost certainly impacted them.”

Madden’s talk will start at 5:30 p.m., Oct. 14, at Marble Brewery’s Northeast Heights Taproom at 9904 Montgomery Blvd. NE.