Why is a little bird tapping on a Los Gatos window?

DEAR JOAN: I live in the foothills and for the past two weeks, every morning between 7 and 7:30, a little bird lands on the frame of an upper window in our bedroom and proceeds to peck vigorously several times at the window, turns away a couple of seconds, sometimes hops to another spot, then repeats this cycle a few times, then flies off, often returning after a while, and then quits for the day.

What bird is this, and what is this strange behavior?  Is it attacking its reflection? If so, why, and doesn’t a bird learn after a while?

— Karl Sprick, Los Gatos

DEAR KARL: The little bird in question is a dark-eyed junco, who has a well-earned reputation for window tapping. They are very territorial, so while it’s a little early for breeding season, your little tapper could have already staked out his territory and is determined to protect it, even if he is protecting it from himself.

Few creatures understand that the birds they are seeing in windows and other reflective surfaces are actually just their own reflection. So they do what’s natural and peck at the intruder to scare them away.

The bird might also be pecking at small insects that could be around the window frame. Because he starts at a specific time and stops after a bit, I think it’s probably a reaction to his reflection. Depending on the time of day, the sun’s position makes surfaces reflective. As the sun moves higher in the sky, the reflective effect fades and disappears, and the bird can no longer see himself.

You can cover the window to reduce its mirror-like properties, but often when trees leaf out, the problem disappears.

DEAR JOAN: I have two types of seed in feeders. One is nyjer, the black seeds. Last year the birds ate it all the time. This year they’re not touching it. Are my other seeds more interesting or do only certain birds eat Nyjer. I’m seeing cardinals and lots of finches.

— Yvonne Moss, Indianapolis, Indiana

DEAR YVONNE: Finches do love their nyjer seeds, but they like them best in winter, less so in summer. The seeds are high in fat, which they need to help protect themselves from colder temperatures.

They’ll also eat them in the summer, but they don’t crave the higher fat so they eat less of them, preferring other seeds. The higher temperatures in summer can also cause the seeds to dry out quickly, which makes them less appetizing.

Birds also can be quite picky about the quality of nyjer. Older seeds often get snubbed, which makes buying Nyjer in bulk a bad idea unless you have a lot of feeders and a lot of birds visiting. If nothing else has changed and they’ve stopped eating them, it could be your seeds are old.

When deciding what to feed your backyard visitors, let the birds have their say. If you find that the food isn’t getting much attention, switch to something else.

In addition to the finches, pine siskins and indigo buntings also eat nyjer. Cardinals are fond of black oil sunflower seeds, fruits and berries, and insects.

The Animal Life column runs on Mondays. Contact Joan Morris at AskJoanMorris@gmail.com.