In a Berkeley park, a bluebird displays unusual behavior

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This young western bluebird — a “helper” — has been feeding wiggling meals to his baby siblings. Photo: Elaine Miller Bond

Last year, Rusty Scalf, teacher and trip leader for the Audubon Society, introduced me to a family of western bluebirds living and nesting in Berkeley’s San Pablo Park. This year, Scalf called me back. Apparently, a “mad man” had flown onto the bluebird scene.

“He’s like a Rambo,” Scalf said. “A worm bandit… a total behavioral outlier.”  “He,” the bluebird shown above, was a fledgling, a few weeks old, which undertook intensive hunting forays across the park. He even “mugged” a house sparrow and competed with his parents, beak-to-beak, for insects and worms — food he delivered to his younger brother and two sisters in the nest.

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Here, the helper male (left, about 70 days old) feeds his little sister (about 23 days old), which recently fledged from the nest box. Both bear the spotted plumage of a chick. Photo: Elaine Miller Bond

The male delivered these wiggling meals for weeks — initially, while the chicks were growing in the nest box, and later, after they had fledged and taken up residence in the trees. Successful pairs of western bluebirds may produce two broods in one season. It’s a special bonus when one of their older offspring (almost always a son) helps tend the younger chicks.

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This youngster just made a food delivery; now he’s scanning the park for the next meal. Scalf built and installed this nestbox for bluebirds in 2010. During the two previous years, bluebirds nested on their own in this tree using a woodpecker’s hole. The branch with the hole was cut off for tree trimming. Photo: Elaine Miller Bond

This behavior — a form of “helping” — is rare. According to Professor Janis Dickinson, Director of Citizen Science at The Cornell Lab of Ornithology, an average of 7 percent of western bluebird pairs receive extra help in tending their nests. Worldwide, only 3 percent of bird species are so-called “cooperative breeders.”

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This is Dad (sapphire blue), having toiled all season to feed two broods of chicks. He may be losing his feathers, but not his sparkle. Photo: Elaine Miller Bond

Feedings by young bluebirds, however, do not provide chicks with a net gain in calories, Dr. Dickinson said.

One theory, instead, is that sons tend to the younger chicks as a form of “rent” — of paying back their hard-working parents for living at home and pecking food in their territory. Most sons spend their first winters with Mom and Dad. Daughters disperse by fall.

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This is Mom (azure blue), hovering over the grass before she pounces. Western bluebirds usually hunt from perches, like trees, poles, wires. Photo: Elaine Miller Bond

Western bluebirds help as adults, too. Grown-ups tending nests not-of-their-own are exclusively male. Their mates may have died, or their nests may have failed.

They then turn their efforts to family members — their parents, brother and sister-in-law, maybe grandpa and his mate — providing extra meals to their chicks. If these chicks grow faster and leave home sooner, Mom and Dad might get a chance at a second brood.

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“Junior” (above) took on the work of feeding chicks with unusual intensity for a gentle bluebird. “I’d love to know how he turns out as an adult,” said Scalf, “whether he’ll continue to show high levels of assertiveness.” Photo: Elaine Miller Bond

To understand why a bird might pour its time and energy into another bird’s chicks, Dr. Dickinson said that scientists perform a special form of “accounting.” They look at an animal’s options and whether the behaviors it employs offer best advantage.

“We talk about inclusive fitness,” she said, “the combined fitness achieved by surviving and producing one’s own offspring, plus the fitness one gets by increasing the number of offspring that relatives produce beyond what they would achieve without your help.”

Given the choice, bluebirds would rather do the breeding themselves. But like the old adage says — if you can’t breed ‘em, join ‘em.

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There’s a new adult in town. As of late July, the young helper male began to lose his spotted chick plumage. Growing in now are his flashy new big-boy feathers: russet breast and blue back. Photo: Elaine Miller Bond

Winter’s mystery

Western bluebirds actually switch their diets, from bugs in summer to berries in winter. No one knows, for sure, where Berkeley’s bluebirds go after they leave their nesting areas, like San Pablo Park, in the fall.

Scalf has occasionally spotted small bluebird flocks in yards around the city, gorging on crops of winter berries. They seem to take a particular liking to catony aster berries, pyracantha berries, Himalayan blackberries, and a few that people cultivate for themselves. Yes, bluebirds on blueberries!

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This may be the city, but a few bluebirds call it home. Photo: Elaine Miller Bond

City bluebird, country bluebird

Oak woodlands, mixed with bug-filled meadows, offer an ideal habitat to western bluebirds in California. Most, in fact, live in rural settings. Dr. Dickson has studied western bluebirds and their cooperative behaviors since 1989 at the University of California’s Hastings Natural History Reservation in Carmel Valley.

But it only takes few bluebirds to spread happiness. Every time I stroll through San Pablo Park with my big camera and Rusty Scalf (“the Bluebird Guy”), people spark up a conversation. They marvel at the bluebirds, their lightness and color, the importance of small glittering things.

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The next generation of Berkeley’s bluebirds. Photo: Elaine Miller Bond

How to help western bluebirds:

  • Keep pet cats (predators) indoors.
  • Refrain from using pesticides; they kill the crawlies that bluebirds eat.
  • Protect old-growth oak trees, the natural habitat and feeding grounds for western bluebirds.

Special thanks to Dr. Janis Dickinson (Cornell Lab of Ornithology), Vincent Voegeli (Hastings Natural History Reservation), and Rusty Scalf, who praises the Golden Gate Audubon Society for its work in bird conservation.

Bluebird breaking news…August 1, 2013, San Pablo Park, Berkeley:

Rusty Scalf, on his near-daily visits to the park, observed the female adult bluebird (“Mom”) hunting very small fly-sized prey — the kind of food she might feed to newly hatched chicks. She then carried the food into the nestbox, perhaps, to a third brood!

Scalf uncovered a few incidents of three-broods-in-one-season in the scientific literature on bluebirds. Dr. Janis Dickinson, in her own 30 years of fieldwork, has never seen it. “Her” birds stop breeding after about June 15. She also notes that her study site rests at higher elevation, and the western bluebirds in San Pablo Park are not leg-banded, which would have given certainty as to who the individuals are.

All we can do now is to wait and see if even more chicks emerge from that trusty nestbox. But the chances, like the bluebirds, are looking bright.

Elaine Miller Bond is the author-illustrator of “Affimals: Affirmations + Animals” and the recently published “Dream Affimals” (Sunstone Press). She is also the photographer for the upcoming book, “The Utah Prairie Dog.”

Related:
Lynxes of the bird world: Cooper’s hawks nest in Berkeley (04.18.13)
The mystery and thrill: Shorebirds enjoy winter in Berkeley (03.21.13)
Rare bluebird sightings bring happiness in a Berkeley park (08.07.12)

Berkeleyside publishes many articles every day. To see all our stories in chronological order, and read ones you may have missed, check out All the News.

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  • Bill N

    This is a wonderful article and very informative.

  • Andrew

    this article is for some reason showing in it’s entirety on the berkeleyside front page rather than the usual …read more link.

  • Neil

    Great pictures and an interesting article. Thank you.

  • Tizzielish

    Thank you, Ms. Bond, and berkeleyside.com for this lovely story. This is positive news about Berkeley I am humbly grateful to read. There is more to life in any city than crime stats, business openings, citizen activism and politics.

    Bluebirds and San Pablo Park are at least as important as other topics. A big loving thank you.

  • BrianY

    Thanks for the article and the amazing photographs. It’s nice to see details like the yellow malar streak on the juvenile’s face–something I’d never be able to spot in the field!

    If this pair is raising a third brood, I would imagine a lot of that has to do with the abundant prey available to them through the efforts of Rusty Scalf and other volunteers, who take meal worms for the bluebirds to the park several times a week. The worms are visible in a number of the shots.

  • PragmaticProgressive

    Funny that “Rambo” is the frame of reference when local examples of thuggish behavior are present in abundance.

  • M.E. Lawrence

    It takes Rambo-like behavior to cope with house sparrows, tough little creatures who will engage in long duels (fighting in mid-air, etc.) over nesting territory.

    Anyway, this is a wonderful article, which I’m sending on to friends and family. Please keep the birds coming, Berkeleyside! They are a great diversion from the depressing acts of certain human animals.

  • Jeff Greenwald

    Fascinating, as always — even to us non-birders!

  • Ryan Mykita

    Agreed – Such a great article. Refreshing change of pace. Now that’s worth paying a membership for!

  • kinglet749

    Very interesting, and special thanks to Rusty for his contribution to Bay Area birding. Just a note… it’s “Cotoneaster” not “cottony aster” or whatever the author thought it was. Nonnative invasive. We should all plant native berry-bearing shrubs so that we don’t aid birds in spreading plant pests.

  • samothrellim

    Eastern Bluebirds have long been chased away by more aggressive English Sparrows. Good to see the Western variety is holding its own!

  • BK

    this is fantastic! Thank you so much! I’ve never seen Western Bluebird photos so detailed and fun.

  • L.

    I have had the good luck to be walking through San Pablo park with my daughter while Rusty was out throwing worms (or whatever they were, grubs?) to the bluebirds. So great to have a local activist for these birds who not only obviously cares for the creatures, but is also cheerfully willing to educate us residents about them! Thanks Rusty! My daughter still pays special attention at the park to see if she can find the ‘special bluebirds’.

  • Moriah

    These photos are breathtaking, and the story is so interesting. Thank you!

  • Barsini

    What a great article with amazing snapshots of the bluebirds. Thank you!

  • John Saggett

    Very interesting

  • John Saggett

    Cool info.