6. Poecile rufuscens


July 22, 2016

This afternoon a sparrow called me from my desk onto the fire escape. Sunny summer overheats the upstairs at the Meeting House, and I prop doors and windows open. North wind, our fair-weather air from the mainland, fluttered papers on desk and floor. The sparrow had no trouble luring me outside. I was happy to escape desk-time worries. Someone camped in Fern Street Park this week.

Before 5:00 on a yard-watering morning I noticed a tent behind the Meeting House fence in the corner by the thicket. The Provincial government recently dispersed a tent city from its courthouse lawn downtown. Some of the people remain homeless and camp in parks around the city. The tent behind our fence is the first I have seen in Fern Street Park. The camper vacated some time before 8:00 a.m., leaving no mess. The only trace I see is zig-zaggy distortion in my right eye from stress.

My concern is with neighbourhood conflict. My friends and I care for beds of local native plants at three corners of Fern Street Park. We favour diverse community of plants, insects, birds, people young and old, renters and homeowners. If our gardening efforts appear to create habitat for homeless people, however, we have a big problem.

Some neighbours vehemently opposed our work in the park. A simple rectangle of lawn beside the children’s play structure had, for years, served their families well.  We designed the planted beds with care for child safety – clear lines of sight and no hidey-holes for lurkers. My fight-or-flight emotions shout, however, that the tent of a homeless person nestled against the thicket would re-fuel opposition to the planted beds I defend.

Before I saw the tent, primitive responses already hooted and thrashed underbrush within me this week. Other North Jubilee neighbourhood projects bristle with conflict. The Neighbourhood Association elected me to chair its board last month. I chair its Greenspace Committee as well. I have taken my new titles as license to act on my dreams for harmony of people and nature in our public spaces. Not everyone is responding as I had hoped though. I embroil myself and my friends in power struggles, feeling beset and contused.

Most bruising is the Spirit Garden path project. The public walkway through North Jubilee’s community garden needs repair. The Neighbourhood Association seeks funding from the city. I volunteered our Greenspace Committee to apply for the grant. We have some experience in shaping projects to attract grant money. Probably we’ll get the grant. But the Spirit Garden path effort is not the friendly, inclusive process I pictured. It has lifted the lid from a simmering pot of old antagonisms, dropped my friends in and turned up the heat.

I listened this afternoon from the fire escape upper landing. Gardeners’ machines howled from a condominium, but wind rustle in leaves invited me home to the back yard. It felt peaceful, in a busy sort of way. In the big maple, I discerned quick twitters and active small birds. Glimpses of white cheek wedged between black cap and bib indicated “chickadee”. Distribution maps in Peterson’s field guide showed just one chickadee hereabouts: “Chestnut-backed”. My Birds of Victoria and Vicinity (1989), confirmed in caps: “THIS IS THE ONLY CHICKADEEon Vancouver Island.”

Habitat for Chestnut-backed chickadee, the field guide encapsulates as “Moist conifer forest; adjacent oaks and shade trees”, which nicely describes Vancouver Island. This hillside would be an “adjacent oaks and shade trees” part. From coastal California to coastal Alaska, the species inhabits portions of North America’s western slope where Pacific air moderates climate and spreads moisture. Chestnut-backed stays west of the Continental Divide.

So this cannot be the chickadee species I banded in Mr. Sanborn’s back yard in Massachusetts in the 1960s. The memory remains in my left hand, grasping gently the small bird, one leg, toothpick-thin, immobilized in my fingers as I crimp the metal band around it. Those were Black-capped chickadee, common, the state bird.

My bird books show Chestnut-backed chickadee’s Latin name as Parus rufescens, but references on the Internet don’t agree. They name it Poecile rufescens. Why the difference? My books are thirty years old. Science had not yet opened DNA as a new page on which to read bird lineage. Chickadees have recently shifted from genus Parusto Poecile. Their whole family, Paridae (tits, titmice and chickadees), has been re-sorted. “This is supported”, Wikipedia asserts, “by mtDNA cytochrome b sequence analysis”. Yikes! – “mtDNA cytochrome b sequence analysis” – a densely technical mouthful. I will attempt to translate to everyday language, which will lead me to an evolution story that might help me feel better about conflict in the North Jubilee neighbourhood. A convoluted mental trick; I’ll try it.

The Wikipedia article gives a translation hint. “Cytochrome b is a protein found in the mitochondria of eukaryotic cells.” OK, “eukaryotic” refers to cells that have a nucleus. Human cells are eukaryotes, as are cells of birds and other creatures more complex than bacteria. The nucleus is the structure in the cell for carrying our personal DNA, directions for assembling our bodies. Another structure in our cells is mitochondria. Strangely, the mitochondria carry their own DNA, separate from ours. So “mtDNA” is the DNA in mitochondria. The anecdote of how it got there involves intense conflict. Thomas Berry and Brian Swimme tell it brilliantly in their book, The Universe Story (1992). I freely paraphrase:

A couple billion years ago, bacteria had already been mutating and evolving for more than two billion years. We had multiplied, dispersed and diversified throughout Earth’s ocean. We had overgrazed the chemical compounds of that rich, browny soup, and faced food shortages. Some of us had mutated and evolved to find a new food source: sunbeams. We trapped sunlight to take its energy.  The innovation succeeded fabulously, but poisoned the planet with our waste.

Our grim toxic waste of that day was oxygen, O2. Sunshine-eating bacteria had developed a solar-powered process – photosynthesis– to make sugar, a high-energy food, from carbon dioxide and water. Both were plentiful. The ocean was mainly H2O, and CO2 filled the atmosphere. So abundant was carbon dioxide that it enfolded the planet in a steamy hothouse blanket. So successful, however, were the sunshine-eaters, so much CO2 did we consume, so diminishing its hothouse cloud, that we plunged Earth into a massive ice age. But that was hardly our biggest problem.

Photosynthesis releases O2. Oxygen gas is reactive, hungry for electrons from other compounds. Before photosynthesis, oxygen had comprised less than 1% of our atmosphere. As the sunshine-eaters produced more and more of it, atmospheric oxygen increased to, 5%, 10%, 20%. It attacked and depleted common gasses of our good air: ammonia, carbon-monoxide, hydrogen sulphide. It bleached air and ocean from their cozy, fecund browns and oranges to deathly blue transparency. It burned not only our foods, but us also, the bacteria. No environmental crisis more dire has living Earth ever caused ourself than the oxygen catastrophe.

Our built-in creativity, our capacity of random mutation, turned the situation around. Bacteria found a great use for O2. A new process – respiration– used oxygen to convert sugar into available energy for the cell. Respiration consumes O2, producing CO2and H2O. So we had closed the loop. Now, solar-powered life could capture carbon dioxide and free it again, make oxygen and use it again. O2and CO2levels in the atmosphere balanced. We have maintained around 20% oxygen, ever since.

Another new capacity – parasitism– now pushed our evolution further along, through mortal conflict. A parasite bacterium would glom onto or invade another bacterium and feed from it. Parasites succeeded and diversified. Meanwhile, host bacteria fought back, evolved abilities for dealing with attackers. Many parasites and hosts fought to the death. Many limped along together hurt. Some found a good fit and partnered to our mutual benefit – symbiosis. One such partnership created mitochondria.

A parasite was taking sugar from its host for its own respiration. By mutation the two of us gradually struck a deal. One partner evolved as generous host and photosynthesizer, liberally supplying sugar and oxygen. The other evolved as resident specialist in respiration, making abundant energy available for both of us. The attacker thus integrated as a being-within-a-bigger-being; it evolved as mitochondrion, little power plant for the larger cell. Well cared-for by its host, the mitochondrion could shed most of its DNA. It still reproduced itself, but from a simpler set of directions, only 37 genes.

Cytochrome b is one of the mitochondrion’s genes. It helps scientists trace bird evolution. A protein, the cytochome b molecule consists of many little base parts bonded into a long chain. The sequence in which it links the base parts varies greatly between different species of bird. Those variations help scientists parse out species and genera. An international effort, The Bird 10,000 Genome Project(B10K), now consults cytochrome b as it sorts the entire bird branch of the tree of life.

Analysis indicates that the tit family first evolved in Eurasia, and genus Poecilebegan to branch-out there. Ancestors of the North American chickadees may have arrived here via the Bering land bridge three or four million years ago. Poecile rufescens(Chestnut-backed chickadee) separated from its nearest sister species, Poecile hudsonicus(Boreal chickadee), approximately 1.8 million years ago. Rufescensthrives in rainforest habitat of fir, cedar and hemlock. Hudsonicushas evolved for harsher environs of spruce, larch and pine.

The most recent ice age, scientists believe, pushed Boreal and Chestnut-backed into separate refugia. Newfoundland, twenty thousand years ago, possibly harboured hudsonicusat the Atlantic edge of continental ice. Rufescenspopulations survived in enclaves on the Pacific edge of the glaciation such as, possibly, the islands of Haida Gwaii. Glaciers receded around fifteen thousand years ago. In the next ten thousand years, taiga forest spread vast across most of Canada and Alaska. Boreal chickadee ranged west and north to populate it. Chestnut-backed chickadee spread east and north to inhabit our moister, milder Pacific slope forest.

Range of the two species meets in zones of transition between taiga and rainforest. Where their ecosystems overlap, hudsonicusand rufescensnest in different habitats. They combine, however, for winter feeding, socializing in mixed flocks with other little brown birds like red-breasted nuthatch, kinglet, bushtit and brown creeper. Flocking with other species creates wider intelligence; the mixed flock responds to more kinds of information, staying safer and finding more food.

Evolution continually separates us and fits us together. Chestnut-backed and Boreal chickadees part ways. Each finds its own fit in ecosystem, thus defining its unique individual being. Where habitats overlap, rufescensand hudsonicusfind a symbiosis. They collaborate for winter feeding. Two different bacteria, a parasite and its host, engage in conflict and attain communion as one cell, with its nucleus and its mitochondria. Billions of cells differentiate and find common purpose as a person or as a chickadee. Splitting, individuating and refitting in expanded community is a truth of evolution.

Humans can be conscious about it. A big birch in the Spirit Garden has died. We leave it standing, expanding our community. The snag may rot and provide nest holes for generations of Chestnut-backed chickadee. In Fern Street Park we put up nest boxes with entry holes of different sizes. A House sparrow can enter a 35 mm hole, but a 32 mm hole serves smaller birds like chickadees.

Pleasant thoughts, yet my ocular migraine persists. I still detest neighbourhood battles. They can feel personal and vicious. Learning to manage with justice and compassion our splitting and refitting – the journey of civility – we have some distance yet to travel.