A Cowbird Cases the Joint

I first noticed the cowbird’s stake-out on May 17, 2022.

The snoop at my sliding-glass door made no attempt to conceal herself as she stared. I wondered: Was she looking through the glass or at it?

Both are plausible answers. It’s well known that collisions happen when birds see bushes, trees, another bird, or the sky reflected in windows. They might also see through a window and spot interior vegetation, like house plants or potted trees. Birds cannot see glass, so both visuals can trick them into a flight that ends in a bird strike.

The Brown-headed Cowbird standing at my door that May morning wasn’t in flight, nor had she struck the window. She seemed intent in her calm gaze, neither threatened nor aggressive.

I grabbed my camera and moved cautiously toward the glass. Would she see me and bolt before I could record the moment? I clicked as I approached. I was just steps from the door when the cowbird appeared to take notice and fled.

The cowbird’s surveillance continued every day until July 3, generally in the morning. She typically stayed for five to ten minutes and often stopped by several times a day. Here’s a clip showing a few seconds of one visit:

Did you notice the odd, askew feather on her side? That’s how I know the same bird visited each day.

She always performed at least one of the floof-hop-bows that had me scratching my head. Male cowbirds do something similar when they go courting or wish to intimidate other birds. Many male birds, and some females, dive-bomb windows to attack reflected ‘rivals’ during mating season. But as for cowbirds, I had to search to find mention of any female intimidation behavior, whether directed to a real or reflected rival.

I found one old journal article describing a rare, female-to-female cowbird intimidation display. It included a bow. It seemed, therefore, that my female visitor was indeed returning day after day to shoo a potential competitor from the premises, not realizing it was her reflected self.

That assumes, of course, that the bird was female. I considered the possibility this bird was a juvenile cowbird. Juveniles of both genders resemble adult females. Could the ruffled feather be part of a molt? I quickly rejected this hypothesis. To explain why, I need to back up a bit and give some background about this unusual bird.

If you’re familiar with birds and birding, you probably know that Brown-headed Cowbirds are brood parasites. They do not build nests. Instead, the female lays her eggs inside other species’ nests. Operating in stealth mode, she surveils area nests and when their owners are absent, she drops in and lays an egg in just seconds. Known as ‘hosts,’ the targeted birds often fail to recognize the egg as foreign. They incubate, brood, and care for the resulting chicks as their own.

So, back to the question of the possible juvenile identity of my visitor. Recall that the video shows an adult male nearby. Here’s a photo showing the male’s proximity to my visitor one afternoon. (You can also see that our deck is under reconstruction, with a temporary plywood floor. These birds stayed away during the banging.)

Juvenile Brown-headed Cowbirds are raised by other species. So, how do they learn to be cowbirds? Researchers have determined that the juveniles are programmed to recognize adult cowbird chatter. They sneak out of the nest at night, listening for their own kind. Those nights are spent learning cowbird behavior by association. With a male in daytime proximity, my visitor was unlikely to be a juvenile.

So… what exactly was the female cowbird doing in her daily visits to my window? It’s fun to imagine she was surveilling my ‘nest,’ forty-seven days in a row. But the more likely explanation is that she kept returning to check for and then dispatch her perceived rival.

In the end, it seems I wasn’t witnessing a stake-out. More likely, it was a cowbird staking a claim.

A CONFLICT, PLUS RESOURCES AND A RELATED KIDS’ BOOK

Full disclosure: Our home is in the treetops. I often must take wildlife photos through glass. If my subjects are nearby, opening a door or window makes them scatter. To allow that photography, we’ve not installed glass-mounted bird-strike prevention products. In our seventeen years here, I’m aware of just two bird collisions. Both birds flew off within minutes. Am I conflicted about choosing photography over bird safety? You bet. Still, the bird-strike rarity makes me wonder if the position of the house somehow minimizes reflection. Or perhaps we—rather, the birds—are just lucky. I welcome any comments and discussions on this topic.

The Audubon Field Guide has a great introduction to the Brown-headed Cowbird.

Here’s a very old but fascinating journal article about cowbird behavior—the one that includes observation of females bowing to intimidate other females.

For more on how cowbirds learn to be cowbirds, check out this Audubon article. Also read this one.

The University of Michigan’s BioKids website has a detailed Brown-headed Cowbird account. The site is designed for kids but its comprehensive accounts provide data and explanations of interest to all ages.

A Birds of the World article explains why birds collide with windows, and how to help prevent bird strikes.

And finally, here’s an activity book suited for the youngest birders: Beginning Bird Watcher’s Book With 48 Stickers, written and illustrated by nature artist Sy Barlowe. Brown-headed cowbirds are not the fanciest or the most popular bird, so I was delighted to find my window snoop featured in Barlowe’s book, published by Dover Publications.

The book is a kid-friendly birding journal. When a child sees an included bird, they affix the bird’s sticker to its fact page and write a few words about where and when the bird was sighted. Just a few facts are included for each bird, so additional tools are needed (binocs, an adult bird book) to ensure successful birding adventures.
If you scroll my website page where I share favorite kids’ books about birds, you’ll find more books I recommend for budding birders.

Image Credits: Carol Doeringer.