Re: First Friday Golden Gate Audubon Society Birdwalk January 4, 2013

George A Suennen


Good to see the group out at Tilden today. I got there a little late
and missed
some of the action.
Group Photo

I did manage to get the Hoodies and Buffleheads on the Lake:
Female Hooded Merganser "playing" with a small fish

Also was able to photograph a few of the others on your list. The only
bird that I could add was a Golden-crowned Kinglet.

Full set of photos at


On 2013-01-04 3:31 PM, Alan Kaplan wrote:


A wonderful mob (many observers) appeared at Tilden Nature Area/Jewel
Lake for our first of the year First Friday Birdwalk sponsored by
Golden Gate Audubon Society: 37 people signed in, another 4 or so came
later. Thank you to all for getting us off on the right foot. Our
theme today was (Dr.) Terry Root's Atlas of Wintering North American
Birds: an analysis of Christmas Bird Count data.

Dr. Root's conclusion was that many birds are limited in their
northern overwintering distribution by the average minimum January
temperature, and the limit of their ability to generate more energy
than 2.45 times their Basal Metabolism Rate. After some back-and-forth
in the literature in the late 1980s and early 1990s, her conclusion is
accepted widely today.

Dr. Root's data were the 1962/63 to 1971/72 CBC counts. A 2007 paper
reviewed the 1975-2004 CBC data for 254 species and found northward
("poleward") shifts of 1.5 km/year (see La Sorte and Thompson, 2007,
Poleward shifts in winter ranges of North American birds. Ecology 88:

Christmas Bird Counts are fairly robust (accurate) over a wide range
of efforts and abilities of "citizen-scientists" like us, with
exceptions for irruptive species (like Red Crossbills), nomadic ones
(Bohemian Waxwings), aggregating species (Red-winged Blackbirds) and
rare ones (Peregrine Falcon). As the skill and knowledge base of
observers improved, corrections have been made (Semipalmated
Sandpipers don't overwinter in North America--a very few may be in
Florida-- but were once widely reported on CBCs). Nocturnal counts of
owls probably reflect the zeal of counters and not the true
distribution of birds.

More about birds in winter on our next First Friday walk (February 1,
2013, 8:30 am, Tilden Nature Area parking lot).
Meanwhile, here is today's wonderful list of 34 species:

Bufflehead (amazing pre-nuptial displays by males: head-bobbing,
nod-swimming, bridling; and females: sidling up to males and inciting.)
Hooded Merganser
Green Heron
Turkey Vulture
Red-shouldered Hawk
Red-tailed Hawk
Virginia Rail (it ran through the group at the edge of Jewel Lake!
Bird O' the Day, for sure !)
Band-tailed Pigeon (120 plus of them)
Anna's Hummingbird
Belted Kingfisher (she flew around a lot but didn't vocalize much)
Hairy Woodpecker
Northern Flicker
Black Phoebe
Hutton's Vireo
Steller's Jay
Western Scrub-Jay
American Crow
Chestnut-backed Chickadee
Oak Titmouse
Red-breasted Nuthatch
Brown Creeper
Bewick's Wren
Ruby-crowned Kinglet
Hermit Thrush
American Robin
Varied Thrush (for a Thrush Hat Trick !)
Yellow-rumped Warbler
Townsend's Warbler
California Towhee
Fox Sparrow
Song Sparrow
Dark-eyed Junco

Best of Boids!

Alan Kaplan

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