Thursday, October 28, 2010


Here it is late October, and the Snow Geese (Chen caerulescens) have made their annual transhemispheric trip from Wrangel Island, off the north coast of Siberia, across the Bering Straits and down into North America. Up to 100,000 or more birds are thought to make this journey, without a doubt the largest crowd of emissaries from Russia to the United States. Forty thousand pairs are thought to breed on Wrangel Island, and they bring with them the young produced each year.

Half of these birds remain for the winter in the Fraser River and Skagit River valleys of southwestern British Columbia and northwestern Washington, the other half continuing down to major wintering grounds in southern Oregon and California’s Central Valley. Many of the birds have been banded on Wrangel Island, and they bear conspicuous numbered plastic neck collars.

This migration, of very large numbers of birds moving from restricted nesting grounds to restricted wintering grounds, is typical of geese, which seem to function best in a highly social setting. They are herbivores, grazing on grasses and forbs in open areas, and there is usually more than enough food for all. If you’re a herbivore, the world is your breakfast (lunch, dinner) table! Especially if you can eat just about any kind of herbaceous green plant.

These large groups of geese probably facilitate mating (the young birds are surrounded by potential mates) and predator awareness (how could a potential predator sneak up on such a large number of eyes and ears?). The major predator of the Skagit Valley geese is the Bald Eagle, but predation is infrequent. Eagles probably get mostly sick and infirm birds, the ones that don’t make it into the air when an eagle flies over and flushes an entire flock (which may include thousands of birds).

On the nesting grounds on Wrangel Island, Arctic Foxes take their toll. But the greatest mortality source of our Snow Geese may be from hunting on their winter grounds. Birds wounded but not killed by shot probably fall victim to eagles and possibly other predators such as Coyotes. Nevertheless, hunting is strictly regulated and has negligible effect on the goose populations.

The average clutch of Snow Geese is about four eggs. Of them, 80% reach hatchling stage, and 75% of those reach fledging. Thus each pair of adults should produce on average about two young each year. Without heavy mortality, this would lead to a population increase, and that in fact is what is happening with Snow Geese throughout most of their range, leading to conservation and management problems. The widespread availability of agricultural land in winter and the opportunity to expand to new nesting areas in the Arctic combine to enhance population growth. The Wrangel Island population is an exception, having been stable in recent years.

Many immatures are evident in the Skagit flocks, in their distinctive gray plumage. The immatures attain adultlike plumage by the time they are one year old but do not breed until they are three years of age. The birds are censused annually, and the percentage of immatures in the wintering population is an easy way to measure breeding success in the previous summer. Young birds of this population pair during their third winter, and the pair stays together until one of them dies; life span may be two decades or more.

The Snow Geese of the Skagit Valley provide one of the most spectacular of wildlife spectacles in the state. Throughout each winter, carloads of people stop in designated parking areas and watch flocks, sometimes immense flocks, of the geese feeding and flying at pointblank range. They are surely the envy of groups of hunters waiting in vain in nearby fields with their “flocks” of decoys. The birds move between feeding areas, so there are often birds in the sky coming and going.

To see a V-formation of Snow Geese approach from high in the sky, then drop toward the ground by dumping air from under the wings, some of them even briefly upside-down, furnishes a thrill for all who are watching. At the last moment of their descent, the birds extend their webbed feet and spread their tail, as if putting on the brakes, flap vigorously, and settle to the ground. Heads down, they move slowly forward, biting off grass blades as they go. Grass is planted in wildlife management areas set aside for the geese.

These flocks should be checked for the so-called blue morph, previously thought to be a different species, the “Blue Goose.” This morph is common in the central Canadian breeding populations that winter in central United States but has always been rare in the Pacific Northwest. Apparently a few such birds have found their way into the Wrangel Island population, and we see them every winter. They are easily recognized by their dark body and white head; the immatures are much darker than typical Snow Geese.

Dennis Paulson

Thursday, October 21, 2010


In North America, more people feed birds than ever before. The number of bird feeders is surely in the millions all across the continent. In some urban and suburban neighborhoods, it seems as if most yards have a feeder or two. However, any quick survey will show that some of them have not been recently replenished. Bird feeding has its aficionados, but not all of them are passionate about it.

So many people feed birds that a cottage industry of feeders and food types has sprung up. A trip to the nearest Wild Birds Unlimited store will make that clear. Seed feeders are among the most common, with a wide variety of seeds, especially millet and sunflower seeds. Look at the ingredients of a bag of some of the fancier seed mixes sometime to see the breadth.

Suet is another ingredient in the cuisine served in many a yard. This fat-based item has always been especially favored by birds during the low temperatures of winter, but there are now many “no-melt” types that provide food during the heat of summer as well. You can get suet now with just about anything in it, from raisins to insect parts. Suet diversity follows the evolutionary pathway common to all of our consumer items, although it’s not clear how much difference all these additives make to the birds.

Presumably most people who feed birds are sympathetic to animals and nature, and surely the majority are environmentalists. But as such, shouldn’t we be thinking about what effects we are having on the birds and the environment? What are the pros and cons of bird feeding?

It strikes me that there are really two positive aspects of bird feeding. First, we are supporting bird populations (or at least individual birds). This is probably not very important during the summer or at any time when there is plenty of natural food available. Most birds live in places that furnish sufficient food and adjust their migratory behavior to the availability of food.

But there is always the possibility of unusually hard times, when weather phenomena make food suddenly more difficult to obtain. The most obvious example of this would be a heavy snow storm, blanketing the ground and all the potential food on and in it. Think of a finch eating weed seeds or a jay digging up cached acorns. Suddenly, these resources would be unavailable, and the presence of a dependable bird feeder could make all the difference between life and death. This could be called “bird benefit.”

The other important positive aspect of bird feeding is human benefit, to bring the birds closer to us in greater numbers. Birds that come to a feeder daily are in far greater density and variety than we would see just by randomly looking out the windows of our homes. This must be a prime motivator for many people who feed birds. Of course, our gaining a better love of and understanding for birds in this way probably benefits the birds as well.

Are there negative aspects of bird feeding? The seeds that spill from feeders are avidly eaten by rats at night; some of them are out in broad daylight! For those who don’t like rats much, this is a consideration, although they are usually out of sight and mostly out of mind. Many people also consider Eastern Gray Squirrels unwelcome pests at feeders, as indicated by the great variety of “squirrel baffles” on the market.

More seriously, bird feeding does affect the birds. Feeders attract birds near houses, and occasionally a bird will be startled from a feeder and fly into a window with fatal consequences. Of course, many birds strike windows even without feeders.

Our feeders also may attract predators, from bird-eating hawks to cats, and by concentrating the prey at a feeding location, the predators may have an easier time capturing them. This is surely the case for cats. Some have even called these locations “cat feeders.” In addition, parasites and diseases are surely more easily spread when birds gather at abnormal concentrations of their food. Seed-eating siskins and grosbeaks may contract salmonella and even die at feeders during outbreaks of that disease.

Hummingbird feeders are particularly widespread; hummingbirds seem to find them readily no matter where they appear. These feeders have been responsible for dramatic changes in the winter range of some North American hummingbirds, and their presence has allowed Anna’s Hummingbirds to greatly expand their breeding range in all directions, including far to the north.

As a resident species, the Anna’s have to take the consequences of a hard freeze and a feeder-owner without the motivation or opportunity to keep the feeder thawed. Perhaps there are so many feeders that there is usually an alternate one not very far away. One consequence that has not been examined is the loss of pollination by flowers that were formerly visited by migratory hummingbirds!

Bird feeding has even become part of the tourist industry. Numerous sites in the New World tropics feature clusters of hummingbird feeders that attract hundreds of individuals of up to a dozen species of hummingbirds, providing education as well as recreation for nature-minded tourists.

In any case, there is no concrete evidence that feeding birds is either totally good or totally bad for them, so we can use our own judgment to decide. We might not put food out because we are concerned that a bird might fly into one of our windows because of the feeders. Or we might put food out just to enjoy their presence, perhaps even helping them survive a cold snap.

Dennis Paulson
Nature Blog Network