13. Thryomanes Bewickii

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September 8, 2016

Fern Street is Bewick’s wren territory. With bravura, as long as I have lived here, males have sung in plain view on treetops. But I haven’t noticed. Thryomanes Bewickii has foraged underbrush, calling out harsh and sharp at the neighbour’s cat. How disconcerting to learn of the bird now. It cracks a self-image I would prefer to maintain, of knowing about nature in the city. Now I consult my books. Birds of Victoria and Vicinity uses capital letters: “THIS IS THE MOST COMMON back yard wren of Victoria.” I search online. Val Schaefer says: “Here in James Bay, Victoria, BC Canada, our ‘signature bird’ may be the Bewick’s Wren.” That’s the problem with old, cherished self-image; you have to keep it in a climate-controlled room. Let fresh air in and it crumbles to dust.

Listening early in the morning on the fire escape lets in fresh air. This week a bold bird voice came from Fern Street Park, from the trees across the field. That was awkward. It meant walking down the field beneath all the apartment and condominium balconies in pajamas and robe on dewy grass in wet slippers to peer with binoculars into someone’s back yard. A little bird sang strongly at the top of a fruit tree.

It sat upright, more like a flycatcher than a warbler, I thought. It sat and sat and sang and sang, giving me time to study. Its tail appeared longer than a warbler’s; its beak also longer, and curved. Wings looked plain and dark; under-parts plain and light. I noted a possible light eye-stripe. I looked-up flycatchers in my field guide and in a local checklist. A few flycatchers are common in Victoria; I listened on my phone to recordings of their songs. None really matched with the bird at the top of the fruit tree. It sat and sat and sang and sang. It cocked up its tail like a wren. I looked-up wrens in the field guide. Bewick’s wren! The songs in Bird Songs of Canada’s West Coast did not really match, but the narrator mentioned that “Bewick’s wren make a variety of perky songs and calls.”

“Variety” perhaps understates. The Birds of North America website reports that a male may sing more than twenty different songs from many high perches in its territory. He repeats each song more than twenty times before changing tune. A graduate student may follow the wren the entire morning to record all his songs. Nor are they exactly like his neighbours’. A young wren, first claiming a territory, learns to sing by imitating the males around him, but may err slightly in his copy. Next year’s young males will imitate his error. Dialects evolve, local and regional. Isolated populations develop distinctive dialects. The bird on the fruit tree probably sang in southeastern-Vancouver-Island-ese. Ocean isolates our Bewick’s wrens.

Crossings between distant islands would daunt our Thryomanes Bewickii. They don’t migrate. The Birds of British Columbia, Vol. 3 (1997) finds no evidence of Bewick’s wren migration in BC. They barely disperse. A study in Oregon showed juvenile males relocating only about one kilometer from home, staking a territory the same year, and defending it permanently. The territories covered only about two hectares (4-5 acres) of thick, shrubby vegetation. Even in sparse habitat, such as this urban neighbourhood, territories might cover only four hectares. The Oregon birds didn’t fly far. Their longest flight might cross a couple of acres, carrying bugs home to nestlings or chasing out an intruding wren. Most flights darted between patches of dense cover, less than twelve meters.

Its stay-at-home habits cause Bewick’s wren to evolve local races. Across the bird’s range from here to Mexico, science currently recognizes sixteen subspecies. Our Vancouver Island wrens belong to subspecies calophonus along with birds of western Washington and Oregon. It seems likely that Thryomanes Bewickii calophonus originally expanded here from Oregon and Washington during a time when warming climate was enlarging their habitat northward. The male that sang from the fruit tree across the park could probably claim ancient ancestry on Vancouver Island.

Its territory might include this entire city block. Aware now of Bewick’s wrens, I have noticed one singing in the front yard from the top of the holly tree and foraging low in the native plant area underbrush. The native plant thicket stacks-up not-badly as habitat. The heart of Thryomanes Bewickii country is dry scrub and chaparral of the US Southwest. Salish Sea coast provides the northwestern extreme of the species’ range. We have dry-enough summers, mild-enough winters and dense understory vegetation. We also have, in the words of the Atlas of the Breeding Birds of British Columbia, “anthropogenic landscapes,” shaped-by-people landscapes. Bewick’s wren has little problem with human presence in its territory. The Birds of British Columbia cites a study that found almost 80% of Bewick’s nests in back yards, on farms or in gardens. Almost half of the nests were in sheds, garages and barns. Nest sites included: “pockets or sleeves of clothing left hanging in abandoned buildings, garage drawers and cupboards left slightly ajar, behind a frying pan hanging on a post…[and inside] a paper bag half filled with nails.” As long as my gardening avoids neat-and-tidiness and allows insect abundance, Bewick’s wren welcomes me to its ancestral lands.

How ancestral? Little brown stay-at-home bird, when did you cross to this island from the mainland? How? Such questions allow fresh air gusting into my self-image vault in a swirl of plaster flakes. I have been happy with my picture of this hillside, valley and creek over the past 15,000 years: Glacier departs; land soon rises from the sea; creek flows down the valley; between 14,000 and 13,000 years ago life rushes in – salmon, willow, warbler, people in boats. I would prefer to maintain my illusion of knowing what I am talking about, but these bird questions make me consult people who know vastly more than I do. I went on a walk led by Grant Keddie.

Grant has served for decades as curator of archaeology at the BC Provincial Museum. Evenings and weekends, he has explored locally for hints of our deep history. He tells of recovering a bison tooth from the trench for a sewer line on Haultain Street. If I understand it correctly, Grant Keddie’s picture of this valley’s past includes a period around 12,000 years ago, dry and cold, of grasslands and of lodgepole pines in open forest, of bison herds (gigantic Bison antiquus, now extinct). The picture does not look to me like year-round habitat for Thryomanes Bewickii. I see landscape more like present-day northern BC, east of the Rockies. Winters here 12,000 year ago look too harsh for Bewick’s wren.

On this Fern Street hillside 12,000 years ago we probably hunted the bison and other large mammals. A backhoe on Orcas Island recently uncovered bones of Bison antiquus bearing marks of our stone cleavers and choppers. Orcas Island is only forty kilometers from here. Archeologists believe that hunters butchered the animal on the ice of a frozen pond approximately 13,500 years ago. Falling sea level in that era was converting enough seabed into dry land that the big animals could cross to Vancouver Island, maybe by 12,500 years ago. Their nomadic hunters would follow them. Did the buffalo hunters encounter any people already living here? How did we humans negotiate that meeting? I wonder.

I could not absorb all the information from the walk with Grant Keddie. I took home confusing scribbled notes and the impression of several big shifts in climate, vegetation, animal and human populations. He mentioned that he hopes to work with Richard Hebda, the Provincial Museum’s curator of botany and earth history, to write our local story since the most recent ice age. I need that article now.

New local discoveries about our distant past are emerging in this century, and particularly in this decade. In Bowker Valley it helps that we sit physically between the BC Provincial Museum and the University of Victoria. Scientists of various disciplines wonder and share information about this region where they live. Master of Science candidates select local topics for their thesis research – Kristen Rhea Miskelly, for example, Vegetation and climate history of the Fraser Glaciation on southeastern Vancouver Island, British Columbia, Canada (2012). Miskelly’s thesis proposes an ice-age refugium for plants and animals on southeastern Vancouver Island. Much land in the hills west of Victoria may have stayed both above water and free of ice throughout the Fraser Glaciation. Grant Keddie suspects increasingly that elk and other large mammals survived on the Island throughout the ice age. He hopes to prove it.

Searching for a truer picture of this hillside, valley and creek since ice departed and land rose from the sea, the most helpful article I have found is Richard Hebda’s Biodiversity: Geological History in British Columbia (2007). My impression from Hebda is that the dry, cold era of lodgepole pine open forest and grassland extended through the valley’s first 3,000 years – approximately from 14,500 to 11,500 years ago. Sudden, severe cooling ended the bison era about 11,400 years BP (Before Present). Deep winter freezing during five cold centuries broke down our grassland and pine forest ecosystems. Shrubby, stunted alder may have colonized. I wonder which large mammals remained in our valley. Which died out, moved out or moved in? Did people follow them? Certainly I don’t see Thryomanes Bewickii here during that cold period – but I see them arrive soon after.

Around 10, 900 years BP, climate turned warm and dry, with hotter summers than today. Extreme low sea levels continued to bare so much of the seabed among the Gulf and San Juan Islands that entire ecosystems could cross over to colonize Vancouver Island from the south. Habitat for Bewick’s wren expanded all around the Salish Sea. Douglas fir forest, with dense, shrubby understory spread into and beyond its present zone. Garry oak ecosystem established here also, and wildfire repeatedly cleared swaths of Garry oak meadow. Between 11,000 and 8,000 years ago approximately, this hillside and valley may have looked much like Oregon oak lands look today. The people likely hunted animals we know now on the Island, and possibly dug camas bulbs in meadow. During decades between wildfires, patches of dense brush would grow among the old oaks, and we probably heard Bewick’s wrens sing.

Climate turned slightly cooler and wetter from 8,000 to 4,500 years ago, increasingly like the present day. More Douglas fir forest moved into the valley. Redcedar forest established in damp soil along the creek. Wildfires decreased. Oak meadow zones shrank. People may have adjusted by purposely burning the underbrush to preserve meadow for camas-gathering and forest edge habitat for hunting. Sea level was rising. Shoreline gradually receded to its present position, with the creek mouth at Oak Bay. Ocean increasingly isolated Island plants and animals, including Bewick’s wren. From about 4,500 years BP, the valley and its people maintained generally the same ecosystems that enchanted fur traders landing in 107 BP (1843).

I feel better already. Acquiring this new information applies cement to the cracks in that old self-image. I hear Bewick’s wren sing this morning from the top of a spruce tree across Fern Street. What’s that you say, little bird? Your song tells me: “Forget this inward-looking self-image business. Sit up straight. Sing out. Stake life’s claim to this hillside and valley. Fight for us when you need to.”