Sometime in late May, a pair of bald eagles in British Columbia’s Shoal Harbour Migratory Bird Sanctuary snatched up two red-tailed hawk chicks and brought them back to their nest — alive.
But this is not the whole story. Yes, currying the favor of the adults would buy the hawklet food, but while they collected that food, the hawklet would be left alone with three bigger, ravenous step-siblings who might not be so accommodating. The hawklet now weighs about two pounds, making him about six times smaller than his eaglet nest mates, said David Hancock, a raptor biologist with the Hancock Wildlife Foundation who’s been observing this saga.
And yet when the adults bring food back to the nest, Hancock said, the little dynamo takes total command.
“I mean he’s got such spunk, you can’t help but admire him,” said Hancock, who, like many people who talk about this interloper, refers to it as a male even though its gender is unknown. “So precocial! So much gumption!”
On Friday, the hawklet — whom some have taken to calling Spunky — actually left the nest for the first time and flew about 200 yards away to another stand of trees. Good riddance, the eaglet trio probably thought. With the little tyrant gone, perhaps there’d be more fish sticks to go around. But the joke was on them.
Hancock says that adult eagles typically stop bringing food back to the nest once their young start to fly. It’s thought that this helps motivate the fledglings to stop freeloading and strike out on their own. Just one problem: Unlike Spunky, the baby eagles can’t fly yet. They’re much heavier than the hawklet, and their feathers aren’t hardened enough for flight. So while the hawklet was off gallivanting, the trio of eaglets sat there like sad sacks of potatoes.
By Saturday at noon, the eaglets had been complaining so vociferously and for so long that the adult eagles gave in and brought a fish. And at precisely this moment, the hawklet returned from his night out and hopped his way into the scrum and onto the biggest scrap of sushi. The hawklet then covered the entire meal with his wings, a behavior known as mantling, which hawks employ to hide their kills from other birds of prey who might be flying by. Shielded from the fish they surely thought would be theirs, Hancock said the eaglets sat inches away from their adopted sibling, staring in disbelief as this runt continued to get the best of them.
“He literally pushed the big guys out of the way,” Hancock said.
And then Spunky gorged himself. He ate and ate until, Hancock said, his crop was so full that he could hardly stand. And there he sat, in the same position, for several hours.
This audacious hawklet among eagles is certainly an unusual sight. But it all kind of makes sense if you look at the situation through the lens of evolution.
“The fact that the eagles are feeding it is actually not surprising,” said Christina Riehl, a biologist at Princeton University. “Natural selection has favored parental care in birds over millions of years. And most birds feed their young.”
In fact, parental care is so strong in birds that a whole bunch of bird species have evolved ways to hijack that imperative. They lay their eggs in other birds’ nests and then fly off. The host birds then raise the invader as their own, often to the detriment of the host birds’ own chicks.
This is what biologists call brood parasitism. And from the human perspective, it can be difficult to watch. Cuckoo chicks are known to eject the eggs of other species from host nests, while honeyguide chicks simply stab their nest mates to death with sharpened beaks.
But the host birds aren’t helpless. Some have evolved ways to identify the adversary chicks from their own babies — either through special markings on their eggs or on the inside of their chicks’ mouths or by secret passwords encoded in song. Once an intruder is identified, well, let’s just say it can be a long way down from nest to ground.
But bald eagles don’t usually suffer from brood parasitism, so they have no defenses to weed them out.
“There’s no reason that bald eagles should have evolved to recognize their own babies,” said Riehl, “because 999 times out of a 1,000, what’s in a bald eagle nest is a baby bald eagle.”
This means that the bald eagle pair in British Columbia has neither taken pity on Spunky nor fallen in love. To them, he’s just another gaping mouth to feed, and one thing birds have evolved to do really well is stuff food into gaping mouths.
In fact, this isn’t the first case of a red-tailed hawk being raised by bald eagles. Spunky is the third Hancock has seen.
The real question is what happens next.
Evolution equips true brood parasite chicks with an instinctual game plan. In other words, a cowbird raised in a warbler nest somehow knows that it cannot stick around and mate with a warbler. But birds like eagles and hawks, species that invest lots of time and energy into parental care, benefit from more experience-based learning. And this could lead to the hawklet’s ruin.
For starters, hawks tend to hunt mice and voles, while eagles favor fish and roadkill. This means that Spunky may find himself trying to be an eagle with the tools of a hawk.
But the bigger issue on Hancock’s mind is that the hawklet has made it this far by bullying his eaglet siblings — which, he noted, seem much more submissive than other eaglets he’s observed. If the hawklet goes out into the world thinking he can dominate other eagles many times his size, the story might come to a close rather quickly.
“I think he’s been learning some bad things for the future,” said Hancock.
Then again, Riehl said it’s also entirely possible that Spunky has an unfavorable run-in with another bald eagle and simply learns to avoid them altogether.
And if he survives long enough to reach sexual maturity? That’s anyone’s guess.
Spunky is a red-tailed hawk who hasn’t seen another of his kind since his sibling was converted into lunch before his very eyes a few weeks back. Scientists who rehabilitate raptors usually use puppets to feed them, to prevent the highly impressionable birds from imprinting on humans. At this point, we have to consider the possibility that Spunky believes himself to be a bald eagle.
Now that the hawklet has fledged, Riehl said it certainly has a chance to keep surprising us.
“I don’t think it’s necessarily doomed,” she said.