Sunday, August 9, 2009

Juncos Raise Cowbirds and Other Yard Tales

Late July and early August is typically one of the least exiciting times of the backyard bird-watching year. The breeding season is over for most species and most fledglings are becoming self-sufficient. Natural food sources are in high abundance, so birds' reliance on feeders is minimal. In addition, it's too early for migration or post-breeding flocking, so the number and diversity of birds in the yard is also minimal. Given all of this, I've been very pleased with what I've seen over the past few weeks. With the help of a recent heat wave, yard activity has far exceeded my expectations.

A fledgling Dark-eyed Junco forages for seed with its father on a warm August morning

Last summer, we were graced with the presence of fledgling Dark-eyed Juncos. Juncos do breed here in the valley, but only in small numbers. It was nice to see that at least one pair decided to breed in our neighborhood again this summer. But I was literally shocked to see an adult Junco stuffing Nyjger seed down the throat of what at first appeared to be a large, plump juvenile finch. After a second, it dawned on me that the "finch" was actually a fledgling Brown-headed Cowbird. I had never witnessed cowbird parasitism before. Cowbirds are the only birds that lay their eggs in the nests of other species (warbler nests are frequent targets). The host species then (usually) raise the cowbirds as their own. While cowbirds aren't exactly my favorite species, I still found this incredibly interesting and exciting. A second fledgling cowbird made an appearance in our yard last week and both are now regulars in the yard.

A Dark-eyed Junco feeds a fledgling Brown-headed Cowbird.

A heat wave descended on Western Oregon a week and a half ago, sending temperatures into the low-mid 100's (it was 101, 105, and 106 at the beginning of the last week of August), and temperatures hung in the low/mid '90s for the next week. Not surprisingly, this meant that the bird baths were in almost constant use. Black-capped Chickadees have been a fixture at the baths, as have Red-breasted Nuthatches, both species of goldfinch and their young, House Finches, Western Scrub-Jays, and Downy Woodpeckers.

There are also signs of post-breeding local movements. A Black-headed Grosbeak visited one of the sunflower feeders early one morning during the heat wave. It is possible that this individual was fattening up before its migration. Just yesterday, the first White-breasted Nuthatch in over two years visited our shaded bird bath. It is possible that the unusually dry conditions forced him to look for water somewhere outside of his breeding territory. Bushtits are flocking in numbers of 15+ again. This is somewhat unusual, as the larger numbers are typically not seen until late September. Male Rufous Hummingbirds have dwindled somewhat in number over the past week (undoubtedly headed South) and have been replaced by females and juveniles. They and the Anna's are constantly fighting over the nectar feeders. Lesser Goldfinches have already increased in number and are eating more than their share of Nyjer and sunflower. It's just a matter of time before the American Goldfinches and Pine Siskins begin to flock as well.

A male Anna's Hummingbird tries to cool off in the 100-degree shade on an August evening

A fledgling American Goldfinch bathes on a sunny afternoon, as a Lesser Goldfinch watches

An unusual White-breasted Nuthatch stops in for a drink

A juvenile House Finch munches on sunflower seed

Despite the fact that we're still in early August, we've definitely passed the apex of summer. American Goldfinches are already beginning to molt (below) and it's just a matter of time before more migrants pass through and the flocking begins.


Josh Callman said...

Thanks for your post about Juncos raising Cowbirds. This morning I saw a Junco followed by two fledglings, one of which was bigger than the Junco. Both fledglings were squawking to be fed. Your post helped me figure out that the larger fledgling was probably Brown-headed Cowbird.

Josh Callman said...

Here is a pic of the Junco and two fledglings from this morning:

BJG said...


Thanks for the comments. I'm sorry that it took me a couple of weeks to reply! (Been on vacation.)

Thanks for sharing the really nice junco/cowbird pics, and I'm glad that I could help.