Why is a bird trying to get into the house--pecking at the window?

Yep.Sometimes they will fly at the window to scare off the competition.
I am not sure where you live but alot of warblers have that coloration where I am at.

It’s not trying to get into the house, it’s attacking it’s reflection in the window – he thinks he has a competitor. It the time of year when testes are swelling (no, really, they shrivel up in the off season, that’s too much weight to carry around all year), territories are being established and defended, and mates are being sought.

I used to have the same stupid cardinal attack his reflection in my car side-view window every spring. If you’re really lucky, you’ll get a woodpecker drumming out his territorial signal on your metal downspouts at daybreak. It’s incredibly loud.

I too have had the male cardinal hurtle himself into his reflection in my glass windows and sliders. He was a slow learner; in fact, he usually knocked himself silly before he stopped.

Roger Tory Peterson, in his “Birds of North America,” had a double-page spread entitled “confusing fall warblers.” They were all grey with some yellow in various places.

(Susan; check the beak. A seed eater has a conical-shaped beak, like the cardinal and chickadees. The warblers eat insects and have a more needle-like beak. That ‘s a first step in making an identification.)

I’m in Portland. The bird seems to have a more conical shaped beak. Thanks for your answers—very interesting. We thought perhaps it was attracted to a jade plant inside, but the reflection idea seems right.

@skfinkel : Check out the yellow-rumped warbler or his first cousin, Audubon’s warbler.

It’s a sure sign you’re using too much Windex! :-)

I see birds hitting the glass so hard they die instantly. They…like people thought there was nothing there. I wonder if your bird is trying to figure this out?

You can put a hawk silhouette on your window to stop it from beating its brains out. Since you are in PDX, I am pretty sure they sell them at the Audubon Center gift shop our by Forest Park.