2011-05-14 / Columnists

Nature Notes

By Patricia Martin

We’ve had a cold, wet spring. Sunny days have been few and far between. Not that this is terribly unusual, but I think we’ve been spoiled by last year’s balmy temperatures. Palm Sunday, April 17, was no exception to the cool weather of this spring, as we had received a bit of snow overnight. Biking home from church, I saw a friend and her dog on the sidewalk near the yacht docks. The dog was quite excited, jumping and looking up at a bird that was perched on a snowy fence post. I stopped and looked at it for a bit. The bird looked quite familiar, but I couldn’t quite place it. When I went home, I pulled out my bird books and looked it up. Appropriately enough, it was a snow bunting.

Snow buntings venture further north than any other songbird. Michigan is in the wintering range, which covers the northern tier of states from the East Coast to the West Coasts of the United States and southern Canada. They spend their summers in the Arctic tundra of northern Canada and Alaska. It was reported in 1987 that a single snow bunting was seen near the North Pole in May.

One of the confusing things about snow buntings is that their plumage changes drastically from summer to winter. In the summer (breeding season) the male has a black back, an all-white rump and head, and a black bill. In the winter the male has a yellowish bill and a golden brown crown and rump. In both seasons the wings and tail are predominantly black and white and the underparts are white. The summer female has a streaky crown and back with a dark bill, and in the winter she is similar to the male, but with a blackish forecrown and darkstreaked golden back.

The male snow bunting I spotted on Palm Sunday was not fully black on the back, but rather a gray color, but its head and rump were white, so it was rather a mix of the summer and winter plumage. It may seem strange that snow buntings are whiter in the summer than the winter, as many animals that change color in the north are whiter in the winter to blend in with the snow (snowshoe hare and ermine, for example). With snow buntings, it is thought that the darker winter plumage may help these birds absorb heat on cold, clear days. When seen in flight, they can look like large snowflakes from below.


Snow Buntings Snow Buntings These are medium-sized birds, a little more than six to seven inches long, with a wingspan of 12 to 13 inches. They weigh in at about an ounce and a half.

The song of the snow bunting is a series of bold, repetitive, hightrilling musical notes, which is generally only heard on the breeding grounds, usually in a fluttering display flight and from the ground, so those of us on Mackinac will probably never hear it. Their call is a whistling “teu.”

In Michigan, these birds are winter residents from late September to mid-May and are also a common migrant. During the cold season, they are often gregarious and occasionally associate with horned larks and lapland longspurs. In the winter, snow buntings prefer expansive areas from farm fields (especially grain) and pastures. In these areas they can scratch and peck to find seeds and grain. They’re also seen along the lakeshore, feed lots, and around roadsides and railroads. It is not uncommon to see them picking up small grains of sand or gravel as a source of minerals and to help in digestion. Buntings also go after insects, when they’re available, and along the shorelines they will also eat crustaceans and mollusks.

Snow buntings are well adapted to cold weather and can survive in temperatures as low as 58 degrees below zero Fahrenheit. In very cold temperatures, they often tunnel in the snow in the shelter of shrubs or tuffs of grass. In the spring, it is not uncommon for them to “bathe” in the snow to clean their feathers.

When spring comes, these cold weather birds head north to the breeding grounds in Alaska and in the northernmost parts of Canada. The males arrive there three to four weeks ahead of the females and the older males arrive first. After mating, they build nests made of lichens, grasses, moss, leaves, in cliffs, in cavities, and under rocks. Nest building takes them about four days. The male feeds the female during egg laying and incubation. The hatching of the four to seven eggs is asynchronous, meaning they hatch at different times, not all at once, so that the nestlings are at different developmental stages and therefore they fledge at different times. Once they’re independent, the young form large flocks. The young are fed almost exclusively on insects.

It is interesting to note that the snow bunting females who nest further north produce more eggs than those who nest a little further south. The general rule is that the way to win the game of natural selection is to produce as many surviving young as possible. Laying too many eggs may result in the death of the whole clutch from lack of food, not being able to incubate them properly, attracting nest robbers and predators, and weakening the female to the point that she won’t survive the winter or may not be able to care for all of the young. Producing too few eggs means that the bird will fledge fewer young than it is capable of rearing. So the number of eggs produced is a tricky balance. Studies have shown that the clutch size is positively related to the amount of food produced (resource abundance) during the breeding season relative to the density of bird population per unit area of habitat. If a habitat produces a large increase in food during the breeding season, the number of eggs that are laid and hatched would be higher than an area that had a smaller increase in food production during the breeding season. This is what happens in the northern latitudes, where there is an enormous increase in productivity in the spring and summer. And this is what happens with the snow buntings.

Most of the snow buntings have now left the area for their breeding grounds in the cold north, but keep an eye out for them next fall and winter.

Trish Martin is a year-around resident of Mackinac Island, has earned a master’s degree in bot- any from Central Michigan University, and owns Bogan Lane Inn.

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