March 16, 2023

Melissa’s dad put up a bird house on the back patio to attract a pair of eastern bluebirds (Sialia sialis) that her mom loved to watch.  It worked and we have had a nesting pair every year except last when the box was taken over early by a pair of house sparrows (Passer domesticus).  The bluebirds got it back again this year and have been busily building the nest which will hopefully hold the clutch of young birds.  While I enjoy watching the birds as they flit in and out of the box scavenging for food, the male has become aggressive protecting the nest.  He is not fighting with the cardinals or jays, but instead with the phantom bluebird he sees in the bay window where Melissa has set up her home office.  Several times a day he will fly into the window and do battle with his reflection.

When I looked online, I found unlike window strikes, birds sometimes repeatedly and aggressively fly at reflective surfaces like windows and mirrors.  This attack behavior is most common in species that nest in the trees and shrubs in the yards that surround suburban houses.  These are often the American robin (Turdus migratorius) and Northern cardinal (Cardinalis cardinalis), and less commonly a Northern mockingbird (Mimus polyglottos), or American goldfinch (Spinus tristis).  The behavior is even found in a wild turkey (Meleagris gallopavo) and ruffed grouse (Bonasa umbellus).  The root of this behavior is territorial. When birds select a nest site, the surrounding area becomes their territory, and they defend it vigorously.  Bird territories vary in size depending on the bird species and available resources.  A typical suburban songbird like our bluebirds only needs a small backyard, whereas a pair of black-capped chickadees will chase off trespassers in a space from eight to 17 acres.

Melissa became concerned by the aggressiveness behavior of our bluebirds.  She was afraid it might injure itself and asked me to look up ways to keep him from attacking the window.  Despite its violent appearance the behavior is very rarely fatal, but birds can sustain injuries and especially to their beaks.  This activity may continue throughout the breeding season, which lasts from May to early August.  Territorial birds can be very persistent and if you cover up the window the bird may search for the perceived rival in another reflective surface.  If the bird is attacking a bedroom window and interfering with sleep, you may want to attach a piece of plastic or drop cloth to the outside.  If you only secure it at the top the wind movement will help scare away the bird.  Methods that do not remove the reflection, like fake owls and rubber snakes, will not deter a territorial bird.  The best course of action is to do nothing and wait.

THOUGHTS:  Reading up on the behavior of our bluebirds reminded me of the Canada goose (Branta canadensis) who took up residence on the concrete patio of our condo in Utah.  I first became aware of his presence at 2:00 am.  The patio had a sliding glass door that led into our bedroom that I slept next to.  We had crazy neighbors who lived upstairs so I was not surprised when I awoke to someone knocking on the glass.  I tried to ignore it thinking they would go away but the rapping persisted.  I got up and turned on the porch light to find the goose rapping on the window, believing it was fighting another goose.  Aside from the mess he caused and the occasionally rapping, the goose was aggressive when we tried to exit the door.  I was glad when he finally left.  Humans can be aggressive when we try and protect territory.  Unlike birds, these violent attacks often lead to injury.  Another difference is we should be able to tell the difference between a threat and a perceived rival.  We can work out our differences but that requires cooperation.  It is worth the trouble.  Act for all.  Change is coming and it starts with you.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s