Thursday, February 12, 2009

Tangled banks

Charles Darwin began the final paragraph of On the Origin of Species by Means of Natural Selection with this vivid imagery:
It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us.
The bank of vegetation along our shore - in what an ecologist would call the riparian zone - is a tangle of fern, sumac, grape, dogwood, gentian and a dozen sedges and grasses. Rooted in muck in the parallel littoral zone is a similarly rich tangle of pondweeds, water lilies, milfoils, bladderwort and eelgrass.

There's a lot to say about the riparian and littoral zones of Stony Lake: their vital functions, their diversity, their degradation and their preservation. One could focus on a single wetland species and consider aspects of its form, distribution, life history and origin in an intellectually robust manner made possible by Darwin. All of these are complex and important subjects which merit thorough exploration.

But for today it's enough just to momentarily reflect on the stretch of shoreline we've come to know well with a modest appreciation of some forms most beautiful and most wonderful.

A number of most beautiful forms flourish within these tangles. Song Sparrows and Northern Yellowthroats nest discretely in the thickets. Eastern Phoebes stuff their chicks with freshly emerged damselflies gleaned from the stems of the rushes. Just below the water line, thick mats of vegetation provide spawning substrate and nursery habitat for many fishes. By early summer, teeming schools of fry can be seen warming themselves at the surface. Some birds follow the fish.

A little deeper in the bay, down a narrow channel through the cattails, the loons nest. Only hours after the young hatch, the family swims out into the main body of the lake to a sheltered nursery area among some small rocky islands. Other fish eaters - mergansers, kingfishers, bitterns, herons and ospreys - nest elsewhere on the lake but forage along our shoreline. Big fish come to feed on the small fish. With the myriad forms comes a tangle of sounds - splashing, squawking, buzzing, trilling, screeching, drumming, warbling, hooting, chipping, rasping, cooing, peeping and croaking, lots of croaking.

Yet this is more than a sumptuous feast for our eyes and ears. Darwin's great insight - that of our shared ancestry - makes it personal and profound. He shattered the arrogant myth of a separate creation and freed us to find community and communion in all living things. That seems pretty wonderful.

Thanks and happy birthday Charles Darwin.

Some people don't like their banks tangled. Here's a disentangled bank.

Related and recent:

Rick Salutin's Valentine for Mr. Darwin (Globe and Mail - 13-02-09)

Verlyn Klinkenborg's
Grasping the Depth of Time as a First Step in Understanding Evolution (New York Times - 23-08-05)

Blog for Darwin

Darwin Online

A Shoreline Primer from Fisheries and Oceans Canada.

Friday, February 6, 2009

A rail jumps the track

On a bitterly cold day exactly three years ago, a resident of nearby Apsley discovered this unfamiliar bird on the street, beneath a discarded Christmas tree. It had a damaged leg, was unable to fly, and was thin as a rail. A few calls were made and the bird was driven to the Toronto Wildlife Centre for assessment. It was identified as an immature Purple Gallinule.

This pigeon-sized marsh bird is common in the tropics and subtropics. In the U.S. it breeds in wetlands along the coastal plain of the Gulf of Mexico with spotty records extending up the Mississippi watershed as far north as Illinois. There have been a few summer sightings in southernmost Ontario but these birds are thought to be individuals that overachieved on their northward migration. A winter occurrence is very unusual.

Unfortunately, the leg injury proved to be very serious and the bird was eventually euthanized. The story is both sad and illustrative.

Some authors describe rails, including crakes, coots, moorhens and gallinules, as very weak flyers and there's nothing in my personal experience to suggest otherwise. I have seen very few rails (other than coots) on the wing. Most often I've heard them and once or twice each summer I'll glimpse a Sora or a Virginia Rail skulking among the cattails. In the hand, they seem lean and bony. They certainly don't have the obvious broad pectoral muscle mass required for explosive vertical takeoffs that we see in Ruffed Grouse.

Yet grouse seem to stay very close to home and rails of many species seem not to have realized that they are weak flyers. Vagrant Purple Gallinules have shown up in Quebec, New Brunswick, Nova Scotia, Labrador and Newfoundland. Others touched down in Iceland, Norway, the Azores and South Africa. There's even a record from the Galapagos (West and Hess, 2002). Several other rail species have a histories of straying across continents and hemispheres. They may not be the best navigators but they seem to be perfectly competent flyers.

One result of all of this poor navigation is a remarkable global distribution that includes Africa, Australia, Eurasia and the Americas. Many oceanic islands have been colonized. Where such islands lack predators, natural selection seems to have favoured those descendants that allocated energy into more earthbound pursuits. The flightless Laysan Rail (Porzana palmeri) was one of many such examples. The progenitor of this species is the Old World Baillon's Crake (Porzana pusilla), a number of which made landfall on Laysan (at the north end of the Hawaiian Island chain) after it was exposed by falling sea levels about 125,000 years ago. The loss of flight occurred in a mere blink in evolutionary time (Olson 1999).

[Alas, it only takes a few years for introduced predators - rats, cats, mongoose, snakes and humans - to wipe out these flightless insular species. The last Laysan Rail died in the mid-1940's. Since 1600, 20 insular rail taxa (of which 18 were flightless) have become extinct]

Our Purple Gallinule should have been wintering in a subtropical wetland in the company of ibises, anhingas and egrets, perhaps in the Caribbean. In finding itself in the coldest depths of an Ontario winter it sealed its fate and demonstrated a familial trait - that of straying - which has allowed the rails to successfully colonize far-flung continents and scores of oceanic islands.

Sources and photo credits:

Olson, S. L. 1999. Laysan Rail (Porzana palmeri), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:

West, R. L. and G. K. Hess. 2002. Purple Gallinule (Porphyrio martinica), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:

Photos of injured Purple Gallinule courtesy of Kim Valenta of the Toronto Wildlife Centre.

Photo of Purple Gallinule on lily pad in Melaque (Jalisco, Mexico) courtesy of Howard Platt.

Range map linked from the Cornell Laboratory of Ornithology.

Related and recent:

A nice series of Purple Gallinule images taken in Guatemala City by Mike at 10,000 Birds.

Rail images from Lake Titicaca by Paul at The Lost Frenchman Blog.

Sunday, February 1, 2009

Weekend feeder update

Again, few changes since the last update. Daily visitors include Pine Grosbeaks (2), Common Redpoll (~10), American Goldfinch (~12), Pine Siskin (~6) as well as one to four each of Hairy Woodpecker, Downy Woodpecker, White-breasted Nuthatch, Red-breasted Nuthatch. A dozen or more Blue Jays rule the roost for several hours each day. A pair of Rock Pigeons put in a brief appearance earlier in the week.

The highlight of the week was a first-time showing by a White-winged Crossbill, this morning. It joined a handful of Common Redpolls on the platform. It's not a huge surprise, give the magnitude of the ongoing crossbill irruption but it's a nice addition to the other finches that frequent the feeders.

A few years ago, we enjoyed watching Red Crossbills at a neighbour's feeder down the road, closer to Petrogylphs Provincial Park, which is a very good place to observe both crossbill species.