By Eric Schroeder
As a horse owner dependent upon a trailer to get into our local parks in the spring, I am vigilant about the trailer’s readiness. My trailer lives at Hossmoor, a 138-acre horse property where I’ve seen over fifty species of birds. It’s also just an eight-minute drive from Briones Regional Park—an excellent place to ride and to bird year-round.
But this spring my horse had been injured and I let down my guard. Walking by the trailer in April,, I noticed that what we trailer owners fear most had happened—a Brewer’s Blackbird was sitting on a nest she had built on the spare battery compartment under the gooseneck of my trailer.
I thought to myself that if she hadn’t yet laid any eggs, I could remove the nest—maybe put it on somebody else’s trailer that wasn’t in use. I approached, the bird flew the nest, and I poked my head in. Four eggs.
Why my trailer? There were 25 other trailers that bird could have chosen! I realized immediately I wouldn’t be using the trailer for a while, even when my horse was sound again. But just how long would that be? On the west coast where Brewer’s Blackbirds are non-migratory, they start pairing up as early as the third week in January and all birds are paired by the second week in February. (I realize now that I should have been checking my trailer earlier—and regularly!—since females built the nests over a nine-day period.)
The nest on the trailer. Photo by Eric Schroeder
Generally, eastern populations of Brewer’s Blackbirds tend to nest on the ground, while western populations built nests in a wide variety of locations—in bushes, in vegetation over water, in vegetable crops, and on available trailer perches. Nests built above ground tend to be built from twigs and weed stems with the rougher outer construction giving way to finer materials around the bowl. Bowls are often lined with horsehair—lots of that where my blackbirds live!
Blackbird nest lining, including horse hair. Photo by Eric Schroeder
Brewer’s Blackbirds are synchronous nesters, meaning that nest building for an entire colony starts at the same time. (If I had been paying closer attention to the blackbirds as a whole population, this wouldn’t have happened!) I discovered the eggs in early April but I didn’t have any idea how long they had been there (or when I might use my trailer again).…

By Maureen Lahiff

On a Golden Gate Bird Alliance trip in late March, an early adventure as part of Birdathon 2017, we had a long, full day of birding on Saturday and a wonderful morning on Sunday. We visited a number of areas around Susanville (Lassen County), and then caravanned to Honey Lake, Jack’s Valley, and Eagle Lake. We saw almost 90 species, including wintering geese, ducks, and other water birds; six hawks and both Golden and Bald Eagles; and sagebrush obligates. But we were there for one primary reason — the privilege of witnessing Greater Sage-Grouse (Centrocercus urophasianus) on a lek.

Greater Sage-Grouse mate on leks

Male Greater Sage-Grouse gather on open areas called leks to strut, dance, and sound off. They raise and fan their spiky tails, show off magnificent white ruffs, inflate bright yellow throat sacs, and make a sequence of distinct sounds, ending with a popping sound as they rapidly deflate their throat sacs, which can hold up to a liter of air. Males competitively display at dawn for up to three or four hours. They typically defend small patches of territory on the lek, just a few yards in diameter, very close to each other. Threat displays between males with lowered heads are common, but among Greater Sage-Grouse, charges and wing-battering seldom lead to injury.

Females choose which male to mate with based on male displays. Researchers have not completely sorted out the science of lekking behavior: Do the females come because the males have gathered and it’s an efficient way to compare them and select mates, or do the females gather and the males follow? What traits are the females looking for? Endurance? Other characteristics that define “fitness?” The male’s only contribution is genetic; the females incubate and raise the precocial chicks.

View of the distant lek by Chris Wills. It took three days in a blind to get this picture of a male Greater Sage Grouse. / Photo by Bob Lewis, not from the recent GGBA trip. Male Greater Sage-Grouse performs his courtship display for a female / Photo by Jeanne Stafford (USFWS), not on the GGBA trip

There are also a lot of evolutionary puzzles, as most of the females mate with a few dominant males.

However it works, birds are faithful to lekking sites generation after generation.

An Aldo Leopold morning

I would describe my lek experience early Saturday as an “Aldo Leopold morning.”…

By Miya Lucas

In the spring and summer, the song of the California Thrasher always puts a smile on my face.  The rapid pulsing, throbbing beat within a continuous melody reminds me of a rhythmic rap song. Often lasting three to five minutes, it’s one of the more varied and complex bird songs and lacks a characteristic, repeated phrase that is easily identified with that bird.

The Cal Thrasher belongs to the Mimidae song bird family. “Mimid” means mimic in Latin, and other Mimidae include our familiar Northern Mockingbird and the Gray Catbird of the East Coast. Although the Cal Thrasher mimics a wide range of species including American Robin, House Finch, and Northern Flicker, mostly it’s known for its own complex song.  One study found 2,807 phrases in a single Cal Thrasher song! Some phrases are repeated like the chorus in your favorite pop song, while others are used only once.

Although you can hear California Thrashers year round, spring and summer are when they’re most vocal.  Even when they sing, it can be hard to spot them. They tend to perch on the middle or side branches of shrubs and trees rather than the top, and their brown heads, wings, and tails camouflage well in the undergrowth.

California Thrasher singing by Miya Lucas

Both female and male thrashers sing. Their songs are usually used for announcing and protecting territory, and mostly sung by the males.  However, if a male bird is clashing with another male who is encroaching into his territory, the female will “stand guard” and start singing until the male returns.  Once the male returns, the female often stands down and stop singing.

Cal Thrashers mate for life, and both male and female help raise the young.  If they have a second clutch, the female typically leaves the first brood while the male stays and continues to feed the chicks.

Males and females look similar. Juveniles have more yellow bordering their underwings than the adults.  The adults have darker bills, while the juveniles’ are brownish. Juveniles’ feet are also more brown, while the adults have dark gray to black feet.

The California Thrasher’s most distinctive visual feature is its long, decurved bill, which it uses to mow through grass or leaves like a farmer using a scythe.  This foraging behavior may be the source of its name – thrashing through leaves and mulch to find insects, spiders, berries, and seeds.…

When Doug Bell heard that a pair of Peregrine Falcons was nesting on the Campanile, he couldn’t believe his luck. An avid falconer, Bell has been fascinated with Peregrines — the fastest animal in the world — since he was a kid growing up in Berkeley. He received his Ph.D. in zoology from UC Berkeley, where he studied ornithology and systematic biology. But never before had he heard of Peregrines nesting on top of the campus’s 300-foot-high bell tower. “It blew me away,” says Bell,  a wildlife program manager with the East Bay Regional Park District.

Peregrine Falcons were once on the brink of extinction, in large part due to widespread use of the pesticide DDT and the country’s misguided assault on predatory animals. In the early 1970s, however, Peregrine Falcons caught a break. DDT was banned and the Endangered Species Act was passed, among other wildlife regulatory laws. In the years since, peregrines have made a remarkable comeback.

As the numbers of Peregrine Falcons have increased, they’ve begun moving from their natural cliff faces into urban areas, laying their eggs on skyscrapers and other tall buildings, such as the Campanile. The following is an interview about the UC falcon pair with Doug Bell and with Golden Gate Bird Alliance member Mary Malec. It’s by Anne Brice, reprinted with permission from Berkeley News, part of the UC Berkeley Office of Communications and Public Affairs.

The female Peregrine Falcon on the second balcony ledge of the Campanile, close to her nest (Photo by Doug Bell)

Berkeley News: When did you first hear about the peregrine falcons nesting on the Campanile?

Doug Bell: I first heard about them in early April. [Birdwatcher Kathleen Durkin, who runs a computing lab in the College of Chemistry, first spotted them.] I thought, gosh, you know, I want to check it out. So on the weekend, I was watching them and it sure looked like they were nesting there. Falcons don’t build nests — they just use a substrate like soil or gravel and make a little depression in it. That’s nice for cliff faces, where they nest in natural situations, but for buildings and skyscrapers that just have cement or steel, there may not be enough substrate around to cradle the eggs, so the female can’t incubate them well. I thought, “We gotta get something under those eggs, so they at least have a good shot at incubating.”…