Posted by: atowhee | January 16, 2020

GETTING CLOSE TO MY NEIGHBORS

UPDATE: I got this email from Dr. Sarah Sloane. She wrote the BNA species account for Bushtits.  Her university post is in Maine so I am convinced she studies Bushtits because they are cool, and they live in warm places.
“In answer to one of your questions on your blog: Both bushtit males and females flock together year round. Small flocks of females may peel off and disperse in early spring. At least that’s what they did in Arizona. I’m not sure yet about the Pacific NW, but I should know soon. Female eye color is fully changed within a few weeks of leaving the nest, so your dark-eyed birds in January are most certainly males! All winter flocks I’ve seen have both males and females, but there is a male-biased sex ratio in general, so females are less common.”
Thanks, Dr. Sloane.  I shall closely surveying our Bushtits for pale eyed ones.

The Bushtits come, the Bushtits go, but they never leave the area.  Somewhere nearby they all pack into a tree cavity at night, sharing  body warmth*.  They are the only member of their genus to live in Americas, their cousins are all in Eurasia.  They share that with the Wrentit, another western bird whose ancestors must have come over from Siberia.  Neither species is a notorious distance flier, not even a migrator.

Today I refilled our suet logs in late morning.  That is their favorite food source though they will use suet blocks or even an occasional sunflower seed chip.  After I re-hung the logs I stepped a few feet to watch.  Within seconds the Bushtits were back.  The bushes were aflutter with tiny wings and  bold with staring eyes.  They ignored me as either friend or irrelevant.  My wife can hear their high-pitched tittering.  Perhaps they were commenting on the excellent cuisine on offer.  I could hear only the faint fluffing of tiny wings beating against air, nano-turbulence creating a sound that hinted at being imagined.  If I closed my eyes I might have thought of falling leaves.

Here we wee one Bushtit come in from the right, talons extended for landing.  Then he lands smoothly:

If I smeared suet on my hat, they might land on my head.  Don’t think I’ll try that.
BUSHTIT GALLERY
I note they all seem to have black eyes, meaning male or juveniles.  Do the females form gender-specific flocks in winter as some shorebirds tend to do, or Red-winged Blackbirds sometimes do?

*Here’s what Birds of North America online has to say about Bushtit body heat and metabolism: “Body temperature 38.6°C () [101.5 Fahrenheit].  Small body-mass-to-surface ratio (average 5.5 g) results in high heat loss. Individuals need to eat about 80% of body mass/d in insects to avoid losing weight (at 20°C ambient temperature; ). When stressed by having less food, individuals lost weight, moved more, and exhibited slight hypothermia at 10°C; unlikely that Bushtits use hypothermia as a way to deal with extreme cold, however ().  Huddling is a major behavioral adaptation for coping with cold. In Washington State, when ambient temperature below freezing, Bushtits perched tightly packed together; when above freezing, spacing is greater (3 cm; ). Huddling conserves both heat and energy.”


Responses

  1. Bushtits make for such a lovely experience. I had taken in the suet for the day (bear) and they came by so I raced to hang it out on my arm. So lovely to feel their soooooo soft bodies on my hand! Question: If I leave suet out in the summer and fall, will they bother with it considering all the seeds around?

  2. Reblogged this on Wolf's Birding and Bonsai Blog.


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