I came across this post from the Voyageurs Wolf Project on Facebook two weeks ago. The page is informative and worth a follow, and this post reveals a fascinating development in the ecology and behavior of wolves!

Of course, this is an April Fool’s joke. At first, I thought wolves were raising a bear, but it turns out these fictitious wolves were raising a sasquatch. It is all very ridiculous.

Enter the brown-headed cowbird, which actually — and successfully — pulls off this very ridiculous stunt on birds across North America, tricking another species into raising its young. While wolves raising bears and sasquatches is absurd; it is also very cute. Cowbirds, on the other hand, do not receive the benefit of the doubt regarding their cuteness when a poor yellow warbler is tasked with rearing a cowbird chick—a yellow warbler which might end up being 1/5th the size of the fully grown cowbird.

*A yellow warbler foster mom with her giant brown-headed cowbird chick. Photo by Emilie Chen FCC*

If we think of the yellow warbler as a full-sized wolf of 70 pounds, the black bear (brown-headed cowbird) it raises will be about 318 pounds, which is well above a healthy black bear male’s average weight of about 275 pounds.

The key difference: a yellow warbler raises that cowbird chick in the span of weeks, whereas the black bear takes at least a decade to become that size.

Sidenote: you can learn even more about cowbirds from Matt Reetz’s fantastic Evenings with Audubon presentation here, or in Carolyn Byer’s awesome Into the Nest feature called Cowbirds, everybody’s favorite villain.

Birds might be crudely classified as “things with feathers,” but that way of thinking obscures the incredible variations and adaptations of species, and the brown-headed cowbird probably gets overlooked despite its fascinating life history. E.O Wilson, in his book The Diversity of Life, states that the test of a complete adaptive radiation is “the existence of a species specialized to feed on other members of its own group.” The cowbird brings a twist to this parasitism; it tricks the host bird into feeding its young.

*A wood thrush with its own and a brown-headed cowbird nestling. Photo by Kelly Colgan Azar*

There are many admirable traits in cowbirds. The females are absolutely prolific at finding nests. Wisconsin just completed its second Breeding Bird Atlas. I participated in the search to find evidence of bird breeding activity—a fun but challenging enterprise. Looking for courtship or copulation, nests with eggs, birds carrying nesting material or food, or recently fledged young, among other things, is tasking. But cowbirds, laying up to 40 eggs in a season, manage to locate and lay eggs in dozens of nests. Upon reflection, I think I should have trained a cowbird female, like a falconer, to accompany my nest-finding expeditions.

Perhaps most impressive, the females then relocate each nest after they lay their eggs. With an enlarged hippocampus compared to males, these female cowbirds have the genius and persistence to bring their eggs into the world.

Mike Ehrmantraut, the famous character from Breaking Bad and Better Call Saul, said “there are two kinds of heists: those where the guys get away with it, and those that leave witnesses.”

The brown-headed cowbird female makes sure she leaves no witnesses. She is Ehrmantraut-esque in her ability to find and stake out the nest. Many scenes in Breaking Bad depict Mike staked out in his car for hours on end, where he eventually notes an interesting habit or behavior of the person he’s watching. Likewise, the female brown-headed cowbird swaps Mike’s 1988 Chrysler Fifth Avenue for brushy fencerows, field edges, and forest clearings—often a result of human disturbance. Here she watches her prospective host, and once a routine is discerned and the host leaves the nest to feed, our female cowbird races to the nest and quickly lays her egg. The deed is done.

But the work for the female is not done. While some opine cowbirds as deadbeats and lazy, the female stays vigilant, watching “her” nests. The cowbird will sometimes appear at a visible spot near the hosts and ensure that the eggs are being cared for. It’s as if the host parents are a witness about to give testimony to bring down a criminal enterprise, but the cowbird appears like a mafioso in the courtroom, and the testimony changes. Again, the behavior might be unsavory, but it is undoubtedly savvy.

What happens if these host birds testify? Many do, and American robins and brown thrashers can successfully eject cowbird eggs and fend off the cowbirds. Other birds will abandon the nest or build a nest on top of the previous one. Yet many birds are maladapted to cowbird parasitism. Researchers have found that when cowbird eggs are removed, the cowbirds will often return to the nest and teach a grisly lesson, destroying the remaining brood. The cowbird philosophy seems again pulled straight from the mouth of Mike Ehrmantrout, who said “The moral of the story is: I chose a half measure, when I should have gone all the way. I’ll never make that mistake again.” There is no half-measure with brown-headed cowbirds; if its egg is ejected, a tit for tat pattern will ensue.

There’s a fascinating Radiolab episode called “Tit for Tat” which explains the prisoner’s dilemma apparent during the Cuban Missile Crisis. One researcher ran a computer tournament where programmers tried to solve the prisoner’s dilemma and faced off against each other. Stacks of code were written, but the winning result was simple. Its first line was “be nice.” The second was “copy the other player’s move.” The program was called “tit for tat.” We see that this is an enthralling solution under this competitive environment. The episode goes on to describe how British and German soldiers, in the trenches during World War I, ended up engaging in a similar sort of scenario. At the lunch hour, both sides learned to cease fire. During Christmas of 1914, British soldiers crawled out of their dark trenches, drawn by the Germans candlelit trees and singing of “Silent Night”. Instead of shooting the exposed British soldiers, both sides decided to have a truce, and they mingled, traded, and drank—and the whole truce lasted a week in some instances. It’s as if, in the darkness of the front lines in December of 1914 the soldiers came together and found their shared humanity.

Back to our cowbirds, at about 20-25 days the juvenile in the host nest will become restless, and like those soldiers during World War 1, the bird sneaks off into the night. These young cowbirds do not find a Christmas truce, but they do find, apparently, their “cowbird-ness.” A clandestine meeting occurs, where the juveniles fly to cowbird roost sites around fields and spend the evening with other cowbirds. Experimental juveniles raised only by their host will end up learning the songs and calls of the host species.

*Brown-headed cowbird club, photo by Patricia Pierce FCC*

So, in a secret meeting in the middle of the night, the cowbird learns that like the popular mafia front of “waste management” the cowbird family business is “nest management,” and the juvenile returns to the host’s nest by morning, its identity known but its disguise burgeoning—the strong, silent type.

Written by Drew Harry, Faville Grove Sanctuary land steward