August 15, 2016
Nesting season gives way to the time of foraging flocks. A new gang showed up this morning, and a different hustle-bustle stirred trees and bushes. At first, foliage concealed the animators. I recognized a chickadee song, and got a brief look at a bright yellow bird, some sort of warbler, but neither chickadee nor warbler powered the event. They only travelled along with it. The thicket vibrated with nondescript, very small birds. I noted their delicate beaks and general browny colouring, lighter below than above, but no distinctive markings. One alit on the back fence and I made note of its “really long tail”. I supposed it was a wren. Peterson’s Field Guide helped me determine they must be Bushtits, “very small, plain birds that move from bush to tree in straggling flocks….” I felt them as a robust, energetic presence.
Bushtit, Psaltriparus minimus, flocks. It maintains year-round, stable membership in its group of four to forty birds. Flock is the greater intellect in which each Bushtit participates, its vital network of communication. Birds of Victoria and Vicinity describes the flock in winter:
“… 15 to 30 move haltingly through the mixed shrubs and trees, hanging upside-down or sideways as they search for insect eggs and larvae. They remain in touch with one another more by sound than by sight, their drab bodies and grey-brown heads blending with the shrubbery. Soft, lisping seeps and twitters are often heard before the birds are seen.”
Their survival depends on constant communication, mostly about food. The winter flock must consume bugs in enormous number daily. Each tiny body, smaller than a chickadee, presents much surface area relative to its internal dimensions, so it quickly radiates away energy. And its metabolism burns hot, maintaining body temperature at around 38.60C. Even on this mild August day, it must eat at least 80% of its own mass in insects, or lose weight. Its job is to keep eating. The flock’s job is to keep finding food.
Every flock member both leads and follows, offers information and listens. It’s a model of teamwork I like. R.C. Miller, a graduate student in California at Berkeley, trailed a band of Bushtits and reported to The Condor with his article, The Flock Behavior of the Coast Bushtit (July 1921). He analyzed the birds’ movements as follows:
“The flock is foraging, let us say, in the outer foliage of an oak tree…. Presently some individual finds the forage poor; no more scale insects or aphids are to be found in its immediate vicinity; it begins to look about in search of fresh fields and pastures green. Yonder is a clump of chaparral that looks promising. A few yards of open space must indeed be traversed in order to reach it, and Bush-tits have a native abhorrence of open spaces; they are natural agoraphobiacs. But hunger is a strong stimulus. The bird hesitates a moment, then darts out and with hurried, undulating flight crosses to the chaparral.
“Other individuals of the flock find food beginning to run short in the oak foliage. They too see the near-by clump of chaparral; they have seen their companion make the flight successfully; they hear his notes, perhaps indicating that he has found food; they themselves are encouraged to make the venture.
“Now the impulse spreads; in groups of two or three or five, others dart across from the oak to the chaparral, until shortly the whole flock has moved to the new location.”
Miller’s image of darting “from the oak to the chaparral”, nicely describes Bushtit country. Typical habitat, my Field Guide lists as “oak scrub, chaparral, mixed woods, pinions and junipers”, from southwestern B.C. to Guatemala. The southwest tip of Vancouver Island, with our Garry oaks, oak scrub and mixed forest, better fits the description of Psaltriparus minimus territory than any other spot in BC. Yet Bushtit is a recent immigrant here, first observed in 1937.
It has far longer occupied the mainland, the lower Fraser Valley. The first printed record of Psaltriparus minimus in BC is from 1866 in John Keast Lord’s book, The naturalist in Vancouver Island and British Columbia. Lord served in the new colony in 1858-59 as naturalist and veterinary surgeon with the British North America Boundary Commission, surveying the Canada/US border. He wrote: “I saw this tiny tit… at Sumass Prairie…, but had no opportunity to observe its habits.”
I don’t get it. Why would Sumas Prairie support Bushtits, perhaps for centuries, when Bowker Valley did not? I have lived in both. Dad worked at the Sumas border crossing for many years. Mom learned a deep sense of place for Sumas Prairie and Sumas Mountain. She admired John Keast Lord and other young British men of science who paid attention to the biological and cultural systems of our coast and left written records. Christie was a writer. But the facts remain, our Victoria climate is drier, our winters warmer, our vegetation more California-ish. What sensible Bushtit would prefer the mainland to southeast Vancouver Island?
I suspect they were simply unable to get here. Remember M.C. Miller’s comment in The Condor that “Bush-tits have a native abhorrence of open spaces….” No Bushtit is going to set out across kilometers of open water toward a dimly visible shore. Nor is the bird built to fly so far. The Birds of North America website suggests that maximum range for non-stop flight, may be about 200 metres.
Then how did it arrive in Victoria in the 1930s? My first guess was island-hopping. Many small islands dot the Salish Sea between here and the mainland. But that solution doesn’t really work. It still involves multiple flights of several kilometers across water. Also, Victoria saw Bushtits before the smaller islands did. Psaltriparus minimus range appears to have spread from this city over several decades, to nearby islands as well as north and west on Vancouver Island. If Bushtits crossed direct from the mainland to Victoria, I guess they travelled by ship. That’s what Mom did when she came to live with Sherryll, Holly and me in the ‘90s. How and why would a Bushtit flock get on a boat? I don’t know, but I welcome them.
I look forward to seeing a nest. Many must hang in bushes in Bowker Valley. The Naturalists Guide to the Victoria Region advises that the “…delicately-woven and pendulous nest may be detected in clumps of Ocean-spray.” Birds of Victoria and Vicinity tells us to watch for “…what one might mistake for an old grey sock hanging from a bushy shrub.” They are marvels.
Building one, a Bushtit pair starts out by lacing a circle of spider silk in the fork of a twig. They intertwine more silk and moss as a small pocket in the circle. Then they continue to work inside it, adding, weaving and stretching it downward. They create a purse, vase-shaped, with narrowed neck and widened lower end. The interior they insulate with fur, feathers and downy plant materials like willow cotton. To the outer surface, they bind flecks of lichen for camouflage.
The nest, well insulated, keeps eggs warm, allowing adults maximum time for foraging. Strong and stretchy, it may accommodate a sizeable group overnight, perhaps fourteen nestlings and adults. That’s a big family. A female may lay as many as ten eggs, and the parents may have other adult helpers. This is a sociable species. Their amazing nests require large investment of time and energy. Predators destroy most of them. Adult Bushtits who have lost theirs often contribute as helpers at successful nests, co-parents.
The bushtit pattern of sociability has served the species its ancestors and its cousins for ages. Its whole family, Aegithalidae, the Long-tailed tits, behaves with remarkable similarity. Of eleven living Aegithalid species, only Psaltriparus minimus is American. Its forerunners, we believe, schmoozed and darted their way across the Bering land bridge around ten million years ago.
The Long-tailed tit, Aegithalos caudatus, isAmerican Bushtit’s closest relative. It thrives over vast portions of Europe and Asia. Like its American cousin, Long-tailed tit feeds in stable flocks of three to thirty birds. Wikipedia’s description of its nest shows striking parallels:
“The nest of the long-tailed tit is constructed from four materials, lichen, feathers, spider egg cocoons and moss, with over 6,000 pieces used for a typical nest. [It] is a flexible sac… suspended… in the forks of tree branches. Structural stability… is provided by a mesh of moss and spider silk. The tiny leaves of the moss act as hooks, and the spider silk of egg cocoons provides the loops; thus forming a natural…Velcro. The tit lines the outside with hundreds of flakes of pale lichens – this provides camouflage. Inside, it lines the nest with more than 2,000 downy feathers to insulate…. Nests suffer a high rate of predation with only 17% success.”
As with American Bushtits, adult Long-tailed tits who lose their nests help with others.
The American Bushtit’s gregarious nature helps it also in winter cold. Birds endure the night clustered in a tight clump. The huddle raises the flock’s ratio of mass to surface area. It presents a smaller out-side, so its in-side conserves heat. Their convivial disposition shows also at winter feeders. As Birds of Victoria and Vicinity describes: “Beef suet hanging… will result in repeated visits from local families of Bushtits. They crowd onto the fat like a swarm of bees.”
Looking at the little bird with the long tail on the back fence this morning leaves me with a paradox. I saw drab insignificance without distinctive marking, contrast or colour, only brownish-grey, grading to grayish-brown on crown and forehead. But I felt vivid animation that sparkled. Bushtit has no audible song, but my heart heard one. Sherryll has a fridge magnet that quotes Rabbi Abraham Heschel: “Just to be is a Blessing, Just to Live is Holy.” The non-descript little brown bird on the back fence sang to me of his or her intrinsic worthiness, and of mine.