Understanding Ravens and Magpies may be the Key to Protecting Our Bald Eagles

Scientists have discovered a mutually beneficial relationship between these birds and bald eagles. Understanding this relationship may help in bald eagle conservation efforts.

By:?Tan Li Tyng Michelle, 1 November 2022

As Americans, we see bald eagles everywhere – on federal agency logos, on our passports, and on the one-dollar bills in our wallets! Found only in America, former President John F. Kennedy remarked “the fierce beauty and proud independence of this great bird aptly symbolizes the strength and freedom of America”. As our majestic national symbol, the bald eagle is rightly “the most pictured bird in all of America”. What a tragedy it would be if bald eagles went extinct! In fact, this terrible future nearly happened in the 20th century, when the bald eagle was endangered. Although they are no longer facing extinction, scientists are continuously striving to better protect our bald eagles.

Thus, in 2019, it was significant when scientists from Oregon State University-Cascades and the Washington Department of Fish and Wildlife discovered a mutually beneficial relationship between birds such as ravens and magpies, and birds of prey such as bald eagles. Understanding this relationship could help us better conserve our mighty national bird.

So many questions!

Why did scientists decide to study ravens and magpies, collectively known as corvids? How did they suspect corvids would have any relationship with bald eagles and other birds of prey, also known as raptors?

One reason is corvids are social animals, just like us. Just like how we communicate via language, corvids communicate with members of their species using a “coded language”, such as by making specific sounds and behaviours. For example, when ravens “circle” carcasses by flying in a circle and diving downwards, other ravens understand food has been spotted and join in.

Sometimes, this “code” can be “cracked” by other species, who can then “hijack” it to their advantage. This code-cracking usually happens when both species have a vested interest in the same thing. Both corvids and raptors eat dead, rotting flesh, also known as carrion. Hence, if raptors could decipher communications between corvids when they discover carrion, they could then understand that carrion has been found and thus benefit by joining in the feast.

Furthermore, anecdotal evidence implies corvids cannot tear or break open an intact carcass by themselves. However, if the carcass is torn open, for example, by the sharp beaks and talons of raptors, corvids can then eat the exposed meat. This suggests corvids also benefit when raptors eat the carcasses they have found. However, this has not been proven experimentally.

Therefore, the team of scientists mentioned previously asked these questions: Can raptors understand corvid signs when they discover carrion, and thus benefit by finding and eating the same carrion? Conversely, do corvids benefit by being able to eat the carcass meat after it has been opened by raptors?

To investigate their questions, the scientists set up two experiments. For the first experiment, they assembled “simulated carcasses”, which included a “fake” deer carcass with no meat. At some simulated carcasses, fake decoy ravens were set up and recorded sounds of ravens were played, to mimic a carcass that was discovered by corvids. Other simulated carcasses had no additional setup. If raptors appeared at both types of simulated carcasses at the same rate, the raptors may be finding the carcasses by themselves, so corvids were irrelevant. However, if raptors appeared more often at simulated carcasses with decoys and recordings than at carcasses without additional setup, the raptors may be noticing corvids, whether real or fake at the carcasses.

For the second experiment, the scientists replicated natural conditions by setting up intact mule deer carcasses and observing the animals that ate them. The scientists could then ascertain if the appearance times of corvids and raptors were correlated, and if corvids could only eat the meat after raptors opened the carcass.

How did the results answer the scientists’ questions?

For the first question – whether raptors benefitted from corvids – both experiments supported the same conclusion. In the first experiment, raptors were significantly more likely to appear at the simulated carcasses with decoy ravens and recordings, compared to those without decoys and recordings. Raptors seemed to be using the presence and sounds of corvids to help them find carcasses, instead of finding the simulated carcasses by themselves.

Similarly, in the second experiment, there was a “consistent” relationship between the appearance times of corvids and raptors. This further suggested that raptors have “cracked the corvid code”, as raptors understand corvid signs when they discover carcasses, such as their sounds and circling behaviour. Raptors then use these signs to find carcasses, without needing to find carcasses by themselves. Thus, raptors benefit from corvids.

What about the second question – do corvids benefit from raptors? The second experiment demonstrated that before the carcass was opened, the corvids could only eat the eyes and flesh around the anus of the carcass. However, once the carcass was torn open by raptors, the corvids switched to eating the exposed meat instead of the eyes and anus. This switch thus indicates that corvids benefit from the ability of raptors to open carcasses.

Therefore, since both corvids and raptors benefit each other, this suggests a mutually beneficial relationship between corvids and raptors!

So what?

This is the first study to demonstrate experimentally that anecdotal reports of corvids benefitting from raptors opening carcasses are true. However, one limitation of the study is there may be other reasons that explain the relationship between corvids and raptors. For example, corvids and raptors may hunt together, like ravens and wolves at Yellowstone National Park. However, as raptors usually appeared “hours” after corvids instead of simultaneously, the scientists believe raptors “hijacking” the communications between corvids is more likely than corvids and raptors foraging together.

Regardless, the scientists are hopeful that this mutually beneficial relationship between corvids and raptors, including our beloved bald eagle, could lay the groundwork for future bald eagle conservation. For example, scientists could start protecting ravens and magpies, as they help bald eagles find food. Us Americans should also hope that bald eagle conservation continues to advance, if we wish to avoid the sad future where we are left without our national bird.