the goldfinch and the spider web

WHAT’S THAT BIRD DOING? This time it was a female goldfinch who elicited the question. She seemed to be pecking at the windowsill (above), but it wasn’t the sill, exactly, that caught her attention. It was a big spider web attached to it. But why?

American goldfinches breed later in the summer than most songbirds, says Cornell Lab of Ornithology’s All About Birds, timing their mating to coincide with peak thistle-seed production. The thistle figures into the equation in two ways: They feed the seed to their young, after they use some of the downy fiber from the seedheads to line their nest.

And what do they use to hold the nest together? Sticky spider-web silk, the preferred Super Glue of other bird species, too, including various hummingbirds, vireos, warblers, bushtits and even the handsome indigo bunting. Apparently the stuff is so precious, at least one species–the cerulean warbler—gathers and reuses it if a second nest is needed after a mishap with the first, says Cornell.

The rufous hummingbird, for example, builds what my friends at BirdNote call a “marvelous nest,” connected with spider silk and covered, for camouflage, with lichen. It looks like this. (The hummingbird above got a bonus bug in its bit of web; photo by Gregg Thompson.)

My goldfinch friend (with a glob of spider silk on her beak, above) didn’t seem interested in bonuses, but webs are often laden with insects—the perfect snack for a busy female bird in search of adhesive, before she continues on her calorie-consuming building project. It’s like she made a trip to the grocery and hardware stores all in one.

what’s that other bird doing?

I’VE ASKED the question before: What’s that bird doing?

• When blue jays pecked off the paint on my porch one winter, I wondered why.
• I asked what’s going on when small birds “mob” much bigger ones, chasing them boldly in the sky?
• Is the cowbird a “bad bird” because it uses other species’ nests, I wanted to know?
• Is that black bird a crow, or a raven?
• What’s all the drumming about, with woodpeckers?

And on and on. Birds make me endlessly curious.

Just the other day, I watched separate performances by the American redstart pair who show themselves regularly by my patio, usually doing a sort of fan-dance (as in the video above) with much spreading of tail feathers and wings. Just what is all that drama about, I asked the showoffs through the open window? No answer—so I asked Cornell Lab of Ornithology’s website instead.

Redstarts, it says, “rapidly spread their cocked tails, exposing the orange or yellow in a quick flash, which often startles insect prey into flushing, whereupon the redstart darts after it, attempting to catch it in the air.” Whatever it’s about, I do love the fan dance, and this flashy little warbler in general.

My friends at BirdNote, the Seattle-based public radio show, had another layer of “aha” on the redstart’s tail, genetically speaking. Listen to this Birdnote segment to find out what the DNA of a male’s tail feathers can reveal. Another answer to a much trickier question, that one.

• All my Q&A interviews with BirdNote are gathered at this link.