January 5, 2017
Chatter of House sparrows filled the back yard at 3:30, an hour before sunset. Their quick shifts perked up trees, shrubs and the ground. A Bewick’s wren clambered and poked on the bark of a trunk. A junco flitted through the garden. In the park a Song sparrow employed its two-footed hop-scratch in the leaves under the birch, and robins enlivened lawn and trees.
By 4:00 sun lit only the treetops, kindling seed cones orange on the Douglas fir at the far end of the park. Bare twigs of the garden thicket did not hide the towhee sitting inside. I reminded myself to open to this place, to make the small motion of mind that brings me alive to it.
By 4:15 sun was gone from this east-facing hillside, but still lit up the tallest poplars in the valley bottom. The Bewick’s wren, Song sparrow and towhee continued to work the back yard. New action high in the horse-chestnut tree caught my attention. A woodpecker was breaking into the globe of a large wasp nest from last summer, ripping and flinging bits of paper. In twilight I saw white markings down a black back. Almost all of the bird’s head appeared dark red. A Red-breasted sapsucker. Last week, at New Years, Sherryll and I watched one beside a trail.
She insisted that I stop and look. Our walk had just begun and myGoals-Fitnessapp was tracking an 8K session. I didn’t want to stop. I know what’s good for me though. Sherryll is a strong walker, but she pauses along the trail to thank individual trees and birds, which annoys me but helps me see. A woodpecker at the path’s edge was gleaning in the bark of an alder, not shy of us, combing for insects. On my iBird Canada app I tapped “British Columbia”, “Tree-clinging-like”, and “Medium (9-16 in)” and got seven matches, woodpeckers. All had markings of red or yellow around the head, but only Red-breasted sapsucker had the entirely red head and throat. We watched until the bird moved into the woods out of sight.
So today I recognized the Red-breasted sapsucker demolishing the wasp nest. Recognized rather than identified. A ten-year-old girl made that distinction in a radio interview I heard recently. She had just completed a birding “big year”, seeing or hearing 227 species. She said that birders prefer to “recognize” rather than “identify” birds. It’s like the difference between identifying a suspect in a police line-up and recognizing a friend on the street. This winter in this yard, most of the birds feel to me happily familiar. This is their place and mine, and I recognize myself at home with them.
I don’t expect to see a Red-breasted sapsucker here often. Birds of Victoria and Vicinity describes it as uncommon in the area and rare in the city, preferring rural woodlands. The Naturalist’s Guide to the Victoria Region directs us to damper locales, west toward cedar and hemlock rainforest or north to mixed fir and maple woods. Winter is probably our best time to see them in town.
This winter the Audubon Christmas bird counters in Duncan, 50K up-island from Victoria, saw BC’s highest number of Red-breasted sapsuckers. Thousands that nest in the interior of the province move out to the coast in autumn, while those that breed here around the Salish Sea remain resident year-round. I would guess that the individual today at the wasp nest was a migrant from the interior, wintering on the coast, seeking insects and suet blocks in the neighbourhood. Does it also maintain sap wells around here somewhere?
Sapsuckers consume tree sap in all seasons. The BC interior, where sap freezes in the trees, cannot serve as winter habitat. Even on the coast, prolonged icy weather in some winters can be deadly. The number of Red-breasted sapsuckers in the province fluctuates extremely, and appears to crash in years with extended cold snaps on the coast. Researchers Wolf Ziller and David Stirling reported on a possible example of such a population disaster on the islands of Haida Gwaii. In 1950 the mean January temperature at the town of Masset was -50C. (230 F.) In an article for the Forestry Chronicle (1961) they note:
“Sapsucker holes drilled at the base of large hemlocks on Moresby Island indicate that the birds were attempting to find food by pecking through thick bark near ground level where cambium was not yet frozen.”
Normally, Red-breasted sapsuckers excavate their sap wells in thinner bark, higher and on younger trees. Walkers in woods on Vancouver Island often see the pattern of square holes they carve. It begins as a row of short slits across the trunk. Each slit pierces the bark to the layer of phloem cells that transport sap. The bird eats the phloem and scoops the liquid that oozes into the slit. The sapsucker tongue has evolved with a brush at the end for licking. They should be called “saplappers” really.
The Red-Breasted, Sphyrapicus ruber, regularly works a circuit of many wells on several trees. It slurps accumulated sap and gradually enlarges the slit into a rough square, resulting in a row of squares across the trunk. As they run dry the bird cuts new slits below. Many rows of squares gradually extend in columns down the trunk. If you see that pattern on a tree hereabouts, Sphyrapicus ruber almost certainly engraved it. The species’ closest cousins, S. varius, Yellow-bellied sapsucker, and S.nuchalis, Red-naped sapsucker, leave similar traces on trees, but rarely stray onto Vancouver Island.
For nesting, the three sapsucker cousin species have BC nicely divided among them. The Red-breasted population centres in mild coastal climate, in coniferous rainforest such as at Haida Gwaii. Yellow-bellied sapsuckers breed mainly in boreal forest of northeastern BC, and migrate far east and south for winter. Red-naped sapsuckers prefer aspen groves of the dry southern interior for nesting. They winter in the US southwest and Mexico. Our Sphyrapicus ruber’s breeding range overlaps with both other species in hybrid zones.
Able to interbreed successfully, ruber, varius and nuchalis were officially lumped until 1985 as races of Yellow-bellied sapsucker. Why did the American Ornithologists Union award Sphyrapicus ruber its separate species status? The more I look into the question, the less simple the answer becomes. Scientists use the term “species” rather pliably, it turns out. Various definitions and standards may apply.
Red-breasted sapsucker defies the most common definition of “species” by interbreeding with Yellow-bellied and Red-naped, and producing fertile offspring. The hybrids can successfully breed. Ruber, varius and nuchalis gene pools do not remain fully isolated from one-another.
Genetically, Red-breasted and Red-naped sapsuckers are the most alike of all bird species. The similarity of their genes would better qualify them for subspecies status. Ruber, with its deeply red head, looks strikingly different from nuchalis, but merely reducing the amount of red carotenoid pigment in ruber’s head feathers would produce an almost typical-appearing Red-naped sapsucker.
Scientists believe that, ruber, nuchalis and varius have been diverging during and since most recent Ice Age. That period contained colder and warmer times, glacial advances and retreats. Variations in climate and ice probably separated the birds’ breeding ranges at some times, but allowed merging and mixing at other times. Around a million years ago, common ancestors of Red-breasted ruber and Red-naped nuchalis began to differentiate from ancestors of Yellow-bellied varius. Later, maybe 500,000 years ago, ruber and nuchalis started to sort apart from one another. Recently, 25,000 to 11,000 years ago during the last glacial advance, isolated populations of Red-breasted sapsucker likely persisted in refugia on Haida Gwaii and Vancouver Island. In warmer climate since then, ruber’s breeding range has intersected again with its cousins, allowing some flow of genes among them.
Calling Red-breasted sapsucker a species recognizes that it has passed a point of no-return in differentiating from its cousins. Genetic mixing among them tends to stay in the hybrid zones of range overlap, not spread much into the wider populations. The hybrid birds seem not to fit in well. They are less successful at passing their genes along to the next generation. Ruber’s distinctly red head may be a factor. Red-breasted sapsuckers prefer mates that look like them. Another factor might be spring migration habits. Ruber has its own timing for arrival in its breeding areas and for courtship. Also, it is distinct ecologically from varius and nuchalis. They do not share Red-breasted sapsucker’s intrinsic fit in coastal rainforest community. The whole package of differences – appearance, physical structure, body chemistry and behaviour – separate Sphyrapicus ruber enough for the American Ornithologists Union to call it a species.
That term has posed a problem for science ever since Charles Darwin’s book On the Origin of Species changed our understanding of how living things come to be. Darwin recognized the problem:
“I look at the term species as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other…. No one definition has satisfied all naturalists: yet every naturalist knows vaguely what he means when he speaks of species. Generally the term includes the unknown element of a distinct act of creation.”
People need common agreement about the different kinds of beings and their names. Prior to 1859 we knew that a “species”, any distinct kind of being, had been created complete, on-the-spot, at-the-moment. Since Darwin and Wallace we know that becoming a distinct kind of being is a process. It advances over centuries or millennia. Speciation is a long conversation in which a physical environment, its living community and a new idea are tussling, modifying, attaining a good enough match-up to become a long-term habit.
Our wet Northwest coast environment, its rainforest community and the Red-breasted sapsucker idea have worked out their fit. Each defines the other. Sphyrapcus ruber has become a keystone species here. Its sap wells contribute food to at least forty-eight bird species, six mammals and dozens of arthropods. Hummingbirds literally follow the sapsucker on its route around its wells, both for sap and for insects it attracts. Availability of sap wells may affect winter survival for Anna’s hummingbird, and migration routes and timing for Rufous hummingbird. Red-breasted sapsucker nest holes provide nest and roost sites for many forest vertebrates. Tree swallow and Violet-green swallow populations depend on them, and Northern flying squirrels may also.
The sapsucker also helps renew mature forest. Sphyrapicus ruber prefers to excavate sap wells in trees that are already unhealthy. The wounds allow fungi to inoculate and hasten decay. Punctures through the bark near the ground in mature conifers, such as Ziller and Stirling described in Haida Gwaii, can let in fungus at the roots. The rot causes giant trees to fall, which opens gaps in the canopy. A burst of new growth results in the openings and maintains diversity in the rainforest community.
Becoming a species is more about linking than separating. We might view speciation as a process in ecosystem for expanding the community’s network of interdependence, its variety and complexity. Same with individuation in humans. We become uniquely ourselves in the give-and-take of matching-up with family, community and place. I modify and discover myself as Sherryll and I negotiate a walk in the woods and a stop to watch a sapsucker, as I garden with native habitat in the yard, the park, the valley, the streambank, as I fight for it, labour with the other gardeners, and include Fuller and Emma.
Next morning I go out to dump compost on the pile. The sun isn’t up yet. From the fire escape I recognize an Anna’s hummingbird tick somewhere above me and a Bewick’s wren rasp somewhere below. We’re home.