Raving about ravens: Researcher provides insights into Yellowstone birds’ travels, interactions

BILLINGS – In the bird world eagles are majestic, swans are elegant and ravens are … amazing.

At least, that might be your conclusion after talking to scientist John Marzluff, who has studied the king of corvids in Yellowstone National Park for decades.

Marzluff, an environmental and forest sciences professor emeritus at the University of Washington, recently gave a presentation on ravens in Bozeman, his chosen retirement community. During his talk, in an interview with the Gazette and in online presentations, Marzluff is ruffling the feathers of raven detractors with insights from studies on which he’s worked.

For example, in 2019, one female raven nesting near Mud Volcano, north of Yellowstone Lake, was captured and fitted with a backpack to electronically track its location and the time of day. In the fall, the bird would often commute 30 to 50 miles one way each day to the area outside the park’s North Entrance, near Gardiner, in search of food. The reason it chose that region was because hunters were shooting elk, bison and deer while leaving behind gut piles and carcasses.

“We had done lots of telemetry over the last several decades on ravens … where if you didn’t find the bird you didn’t get a location,” Marzluff said.

Telemetry was the predecessor of modern GPS tracking, using radio transmitters and receivers. GPS, on the other hand, provides more detailed data that is automatically downloaded to cellphone towers and can be uploaded onto researchers’ computers far from the raven’s location.

“With these new trackers, anywhere they go we’re going to know it,” Marzluff said, citing incidents of other birds commuting from within the park to Cody, Wyoming, or the Beartooth Mountains to feed. “And that’s been amazing to me.”

Long flights

One of the other monitored birds providing amazing information that Marzluff recounted was a juvenile raven that flew more than 400 miles north from Yellowstone to Calgary, Alberta, in the first four months of its life. With large wingspans, ravens are efficient fliers, effortlessly traveling at speeds up to 30 mph.

Another collared bird flew 100 miles in an almost straight line from Billings over the Beartooth Mountains to feed on a carcass in Yellowstone’s Soda Butte area, southwest of Cooke City.

“When we first saw it we wondered how they could possibly know where this (carcass) is,” Marzluff said. “But the more we saw it we realized it’s just a strategy.

“We can’t rule out that it was led there by another Billings bird, but I don’t think so.”

Territorial nesters

Ravens, like many predators, have territories they patrol in search of food. When nesting, that territory in Yellowstone can stretch 3 miles or more. During the spring and summer, the Yellowstone ravens keyed in on insects for food, flipping over piles of bison dung or staking out salmonfly hatches along streams. By fall, when insects are less available, the breeding birds may expand their search out 18 miles or more from their nest site.

Birds that weren’t breeders may often gather at facilities like wastewater treatment plants, where there’s an endless source of fat floating to the surface of ponds that they eat. Visitors to the town of West Yellowstone may see them near the McDonald’s restaurant searching for dropped French fries. Birds have also been regularly observed begging in construction zones where vehicles are forced to stop.

Ravens in the wild can live for 10 to 15 years. Nesting mates are joined for life. When one dies, however, it will be quickly replaced to ensure the survivor maintains protection over the territory.

Breeding pairs of ravens aggressively defend their territory and its food sources, attacking other ravens that attempt to join the feeding frenzy – sometimes even breaking wings in the brutal assaults. For some reason, once nine birds arrive the breeders become less belligerent.

“A lot of the noise you hear at a kill are these young birds kind of vying for status and space,” Marzluff said, with the lowest status birds feeding last.

The cacophony of so many ravens may attract the attention of other birds from as far as 5 to 10 miles, he estimated. One study in Wyoming found ravens were attracted to the sound of gunshots. Other loud noises, like bullhorns or car doors slamming, didn’t produce the same curiosity since there was no food reward.

Even the breeders’ own young are forced to leave their parents’ territory about a month after they’ve fledged. These nonbreeding ravens will often roost in groups. Unlike their relative crows, however, their social connections are loose or nonexistent.

“It’s not like a cohesive flock,” Marzluff said. “They aggregate where it’s worth it … from their individual standpoint. And they have to aggregate to overpower the more dominant territorial holders of the area … or they probably won’t get in to eat much because the resident bird will attack.”

Magpies and wolves

At kill sites in Yellowstone, magpies are often the first to arrive, since there are lots of them and they have a good sense of smell, Marzluff said. They are also fast fliers and bold, sneaking in when predators are still feeding to grab a mouthful.

Although birds can’t eat a lot, maybe a quarter to a half-pound for an adult raven, they will stash food nearby by burying it. In that way, they also inadvertently feed other scavengers like coyotes and foxes. One study showed ravens caching or eating half of a 600-pound moose. Another found ravens could remove up to 80 pounds of meat a day from carcasses killed by wolves.

Dan Stahler, Wolf Project leader in Yellowstone, was the lead author of a 2002 paper looking at the relationship between ravens and wolves. According to the park’s website, about half of the park’s 200 to 300 ravens live in the Northern Range where the densest wolf habitation occurs.

“Ravens were found to be in close association with wolves when they were traveling, resting and hunting prey,” Stahler and his colleagues wrote. “In comparison, ravens showed no significant association with coyotes, elk or areas on the landscape in the absence of wolves.”

Although the scientists always found ravens at wolf kill sites, when they placed carcasses on the landscape to see if ravens would find them, the birds rarely swept in to feed.

“Our results show that ravens’ association with wolves is not just an incidental and proximate by-product of the presence of fresh meat,” Stahler et al. wrote. “Instead, we show that ravens preferentially associate with wolves in both the presence and absence of food, resulting in the discovery of carcasses and suppression of ravens’ innate fear of novel food sources.”

Wolves will chase off scavengers, who often wait out of reach to sneak in for a bite.

Time to revise?

To call someone a bird brain is an insult, meaning they are foolish or dim. But based on the research of scientists like Stahler and Marzluff, maybe it’s time the definition for that slur is revised.

Tracking ravens has shown they are incredibly competent when it comes to things like navigation, responding to sounds and remembering sources of food. In Yellowstone, the birds learned to open hatches on snowmobiles to access visitors’ food.

“We know they can sense magnetic fields and other geographic cues,” Marzluff said. “There’s a world of information they’re tapped into that we’re just starting to understand.”