While gardening outside our sunroom last week, I discovered two gorgeously plumed male black-headed grosbeaks dead below a window. They lay side-by-side, heads pointed toward the window.

Seeing a window casualty always saddens my heart but two of the same species, dead at the same moment, caused me to reflect on what may have happened.

I gently picked up one bird and examined the fresh butterscotch colored body and the striking black-and-white patterned wings. Then I turned the eight-inch bird over to see the rich orange-yellow belly. The bird’s large pale-gray bill shown against its black head. Why would both these male birds die together under my window?

Male grosbeaks along with most other male songbirds are testosterone-driven machines at this time of year. They establish breeding territories, attract a mate and adamantly defend those territories from any other male of their species who might flutter in, or deliberately try to overtake the territory.

Grosbeaks migrate north from Mexico and arrive in our garden every spring around the beginning of May.

First the female appears at our feeders plumed in subdued browns with a strongly striped brown and white head pattern. A few days later, the male joins her. The male sings his “drunken robin” song from the tops of trees and I expect they nest in the wooded ravine next to our house. The window into which the two males flew faces that ravine.

I was reminded of a conversation the week before with a caller who mentioned a robin flinging itself at her window. Hour after hour, the male robin seemed to attack the window, even leaving tiny spots of blood.

I had to explain to the caller that this was common behavior with robins and other songbirds trying to defend a nesting territory. The male birds see their reflection in the window and try to chase it off. This bird behavior is called “battering robin syndrome.”

Robins seem to be the most noticed birds displaying the behavior, but sparrows, wrens and many other local birds also batter themselves nearly to death.

I’ve written about this before, but it seems appropriate to again mention that to keep the birds from seeing their reflection you need to break up the reflective image on the outside of the window. Drawing the drapes inside won’t help. You may want to tape paper to the outside of the window or apply a whitewash. Usually a bird must perch somewhere near the window to notice the “intruder.”

These protective measures need only be applied to specific spots, near a windowsill or where shrubs offer close-by perches, not the entire window. Once nesting season ends, the bird’s territorial urges subside and these preventative measures can be removed.

I am guessing my two male grosbeaks suffered from a different window problem: They couldn’t see it and attempted to fly through. Perhaps one bird was chasing the other out of its territory and they both hit the window with enough force to kill themselves.

When birds can see through to daylight on the other side such as with corner windows or when opposite windows offer a tunnel through the room, they attempt to dart through. In this case pulling drapes does help. Also, breaking up the window surface with decals, hanging wind chimes and reflective ornaments helps alert the birds to go around. Decals of hawks or owls help because they break up the window; but they don’t fool the birds into thinking a predator is present. And if you need an excuse to neglect washing your windows, this is it.

All this reflection leaves me chagrined that my desire for large picture windows has resulted these deaths. I’ll follow my own advice and add more distractions to that window.

Window deaths may pale in significance compared to habitat loss, pesticides and outdoor cats, but all these actions contribute to the dramatic decline in many bird populations.

I promise to stay more vigilant to do whatever I can to protect our feathered friends.

Frances Wood can be reached at wood@whidbey.com. She is author of “Brushed by Feathers: A Year of Birdwatching in the West” (Fulcrum Publishing, Golden, Colo.) available at local bookstores.