August 1, 2016
This morning the back yard on Fern Street was quiet compared with downtown Mexico City. House finches there have evolved a higher pitched voice to communicate above the Mexican capital’s deep urban din. In Victoria the House finches can hear each other more easily, no doubt. Probably I could hear them, but wouldn’t recognize their voices. When I listened at 8:30, first I noted crows, gulls and a seaplane, then hospital ventilations fans, voices of little brown birds (LBBs) and door machinery for underground parking, but not much traffic. On a public holiday, people were probably sleeping in.
My notes from 8:30 proclaim:
“Beautiful! I have hoped for this! An LBB with a red breast and forehead landed on a kale plant. They are there for him, partly. Don told me that he lets his kale and arugula go to seed partly for the seeds & partly because the House finches like them….”
The little brown, vermillion-fronted bird perched briefly to pick at seedpods. Finding them spent, he flew off. Red Russian kale loves it here. I follow the example of Don, my fellow gardener at the Meeting House, leaving a few plants to self-seed. No need to sow, just move little plants where I want them. We have kale all year. I wish we had amaranth also. Amaranth seedheads in North American fields have suppliedHouse finch males with red pigment for ages.
House finch is a native American bird. How deeply native, science has recently revealed. My out-of-date bird books give House finch the Latin name, Carpodacus mexicanus. Recent sources place the species in a new genus, Haemorhous. The old name, Carpodacus, included House finch within the rosefinch family, widespread in Asia and Europe. DNA analysis now shows that the three American rosefinches don’t really belong in Carpodacus. They diverged from their Eurasian cousins around thirteen million years ago. House finch now shares with Purple and Cassin’s finches the American rosefinch genus, Haemorhous.
Modern science first noticed House finch in the dry lands of Mexicoand the US southwest. Hence the species name, mexicanus. It had been there a while. Fossil records place Haemorhous mexicanus in California and New Mexico half a million years ago. Its habitat spanned desert, grassland, scrub and sparse forest. The finch fed mainly on seeds of low plants on open land – amaranth, for example. Open land, but not bare. House finch typically chose habitat with enough bushes or trees to provide roosting above the ground and to supply some edible fruits, berries and flowers. It chose dry lands, but not waterless. People in the arid southwest and Mexico learned that seeing a House finch signaled water nearby. Classic habitat follows the stream along the bottom of a dry valley.
Humans first entered House finch habitat ten to fourteen thousand years ago. We have evidence almost that ancient. In sagebrush parklands at Chance Gulch in the Colorado Rockies around 9000 years ago, our family hunted and gathered. The sight of willow trees down in the gulch invited us to water. We found a good spring and camped near it. We hunted bison, deer, pronghorn, smaller animals and birds. Archaeologists have found the bones around our hearth, including Haemorhous mexicanus. If I feel uncomfortable imagining my family killing and eating House finches, I remind myself that we were stone-age folk at the time; just staying alive was a dominant concern.
“My family”, I say, “we” sat around that paleo-american hearth beside the spring in Chance Gulch. I claim for myself and for anyone who might read these words, direct biological descent from the most ancient Coloradans. The assertion is tentative but not ridiculous. Mathematicians and computer scientists at MIT and Yale examine our ancestry and suggest that all humans alive today may claim a completely identical set of ancestors as recently as five to fifteen thousand years ago.
Douglas Rohde, Steve Olson and Joseph Chang authored a letter to the journal Nature (September 2004), Modelling the recent common ancestry of all living humans. They pointed out that human lineage doesn’t just diverge; it also mixes back. Their thinking changes my picture of peopling the Americas. My old mental map of migration showed one big arrow crossing the land bridge from Siberia to Alaska and curving south down the Rockies. The arrow, splitting and re-splitting would reach into all corners of the Americas. The old map would suggest a one-way, one-time event. The new map would show multiple flows that curve into loops and eddies, mingle, coalesce and generate new currents.
Genetics, Archaeology, Anthropology, Linguistics, Mathematics, all blossom in the 21stCentury and share their information. The picture now shows three distinct migration streams from Asia. One moves down the Pacific coast to South America, another down the Rockies and the third across the Arctic to Greenland. The currents meet and swirl together. Migration also curls back from South America into North America, and back from Alaska into Asia.
The Bering Strait and Aleutian Islands portion of the mental map, I zoom up larger. Many little arrows cross between Asia and America over recent millennia, as many little boats carry people back and forth. The Bering Sea appears not as a barrier to migration between Eurasia and America, but as a link. Whatever portion of the map I enlarge, I see people meeting from every direction. Humans perennially relocate. We invade, raid and trade. We follow our food source or our star. Things go wrong for us at home and we end up in a different place among different people. New blood finds its way across every social taboo and geographical feature to the most isolated caste and island. Humans demonstrate a powerful natural proclivity for mixing our ancestry. “There isn’t an ocean too deep, a mountain so high it can keep”, as the song says, bloodlines apart, in the Stone Age or now. It’s good. It keeps our gene pools rich, and our species adaptable.
It also keeps everybody more closely related than we previously thought. Viewed from space, your family tree looks more like a global network. We all may be biological children of the first humans who camped at the mouth of Bowker Creek just down the valley from this Fern Street hillside. We all may descend directly from the family that snacked on Haemorhous mexicanus around the hearth in Chance Gulch 9000 years ago
About 7000 years ago, our relationship with that bird deepened. We invented farming in Mexico. We domesticated amaranth and surrounded ourselves with it as our cereal staple. We built dams in dry valleys for irrigation, raised windbreaks and houses. Our efforts provided food, water and off-the-ground roosting and nesting for the little brown bird with the red front. Human-altered landscape invited it to settle into its new “House finch” era.
Haemorous mexicanus likely adapted as a Mexico City bird in Aztec Empire times. Known 800 years ago as Tenochtitlan, the Aztec capital housed 200,000 people, grew huge crops of amaranth and imported 180,000 bushels of it annually as imperial tribute.
In recent centuries our human houses, towns and cities have greatly multiplied. So has Haemorhous mexicanus. In Denver, Dr. W. H. Bertgold wrote A Study of the House Finch for the journal, The Auk, in 1913. He noted that:
“The characteristic native bird of the cities and towns of Colorado is the House Finch…. Previous to the advent of the English Sparrow in Denver…the only bird at all common about the buildings… was this finch….In 1881 when the writer first visited Colorado….the House Finch had already taken advantage of the opportunities afforded by… barns and other buildings, to construct nests thereon….”
North America’s changing landscape of farm, city and suburb attracted Haemorhous mexicanus to expand its range in all directions. Along arid valleys northward into Oregon and Washington, we irrigated, planted and built towns. The bird followed. By 1935, Ian McTaggart-Cowan noticed House finches in the Okanagan, a dry valley in British Columbia’s southern interior. He noticed them also here in Victoria.
Briony Penn comments in her McTaggart-Cowan biography, The Real Thing, that he had just returned to BC in 1935 from the University of California, Berkeley, where the House finch was common and familiar to him. She quotes him: “…the House finch song was still echoing in my mind. I was walking to work past the Crystal Pool [in downtown Victoria] and there it was. Its nest was within my reach and they raised three broods that summer.” Only in Victoria, nowhere else in coastal BC or Washington did we see Haemorhous mexicanus in the 1930s.
Coastal rainforest was not its habitat. Damp was not its climate. Ours was – Victoria, driest city on the BC or Washington coast. A few House finches had jumped, it appears, from Penticton in the dry Okanagan Valley, 150 kilometres across the Coast Range, coastal plain and Salish Sea to roost in the ivy on the Empress Hotel. Scientists report that House finches have commonly made such hops, known as “jump dispersals”, as the species has expanded its range. From an established population, a few birds relocate thirty to 180 kilometers distant and breed successfully. That new population then builds up locally and diffuses regionally.
Victoria’s House finch population gradually diffused up Vancouver Island’s east coast. It also jumped back across water to the mainland. We noticed them in Vancouver around 1950, in Seattle by the mid-‘50s, and all around the Salish Sea over the ‘60s and ‘70s. House finch has acclimatized now to damp Pacific Northwest conditions. It thrives, in fact, in diverse climes across North America.
Introduced in New York in the 1940s, for example, the bird rapidly evolved a more-compact shape for surviving cold, snowy winters: shorter legs, feet, wings and tail. It grew a bigger bill that could crack the sunflower seeds in New York feeders. Atlantic-coast-hardy, Haemorhous mexicanus extended its range rapidly south, west, and also north into Canada. It spread into Ontario during the 1970s and ‘80s, Quebec and the Atlantic and prairie provinces in the ‘90s.
Numbering anywhere between 267 million and 1.7 billion, House finch shows up as a strikingly adaptable species – like humans. Back home in Mexico City, for example, the bird has acclimatized to extreme urban conditions. Scientists have shown city finches to focus calmly on food-finding tasks amid levels of human hustle-bustle that totally fluster a country cousin. Mexico City birds have also adopted a new chemical pesticide for controlling ticks that infest nestlings: parent birds line their nests with used cigarette filters.
Like humans also, House finches are disposed to leave home and find mates in some other community. Only twenty percent remain local and breed in their natal population. Juveniles move away in all directions, commonly less than twenty kilometres, but some disperse as far as 1200 km. Adult birds likewise tend to spread out and relocate after breeding season. Like us, House finch is disposed to mixing and remixing its ancestry, continually refreshing its gene pools.
Next year, I promise the House finches: I will sow amaranth. West Coast Seeds sells packets of Burgundy Grain variety and Hopi Red Dye. I hope, next August, to watch a little brown bird with red-ochre forehead, breast and chin munching from an amaranth seedhead atop its tall stalk. Self-seeding, amaranth might settle-in here like the kale. The Meeting House garden might join in an ancient North American relationship.