Golden-crowned kinglets are one of the smallest birds to spend the winter in the cold New England woods. They are not much bigger than a hummingbird and weigh as little as a nickel or as much as a quarter. How does a bird this small stay alive during the long winter night with nothing to fuel its metabolic flames?

To make it even stranger, kinglets only eat insects. You?ll never see one at your bird feeders. Woodpeckers, nuthatches and chickadees eat insects too, but they can also eat seeds and suet. Most insectivorous birds of the north woods avoid the energy crunch by migrating to more benign climates when insects become scarce.

University of Vermont scientist Bernd Heinrich wondered what kinglets were eating in the winter. He found that although they are fairly opportunistic, eating everything from spiders to insect eggs, they subsist primarily on moth caterpillars found on trees.

Even with the ability to find plenty of insect food in the seemingly sterile winter woods, it would be physically impossible for them to survive the night unless they had a special place to roost. Researchers in Virginia found that kinglets could slowly build up enough fat during the day to fuel their metabolism for just half the night. Their daytime diet was not the answer.

Several biologists had suggested that kinglets survived by sleeping in shelters such as old squirrel or bird nests or by huddling together at night. Enter the ever inquisitive Heinrich again. After dozens of attempts to follow kinglets foraging in late afternoon and evening, he was finally successful during twilight one December evening.

Heinrich reported his observation in the Wilson Bulletin, a journal of ornithology,??at 4:20 pm I saw three kinglets fly into a brushy white pine. In less than a minute I found four kinglets huddled together about 4 meters above the ground under thick branches.?

He returned an hour later with a step ladder and a camera. The birds remained huddled together through the night with their heads tucked into the back feathers and just the tails sticking out. The temperature went as low as 14 degrees that night.

The smallest winter bird in the north woods transforms itself into a big bird creating a lower surface area to volume ratio. They radiate less body heat per unit of mass, enabling them to conserve heat and survive a frosty New England night.

Other bird observations this past week featured reports of ?lingering? and ?late? migrants during the unseasonably warm December weather. Three ruby-crowned kinglets were found during the Winhall Christmas bird count. Two late-migrating red-necked grebes were spotted this week, one at Delta Park and another on Lake Bomoseen on December 12. There was a late sighting of an American widgeon on Lake Pinneo

in Quechee and a northern pintail in Windham on the 15th. A late yellow-rumped warbler was found in Quechee.

A red-bellied woodpecker was seen in Pownal on December 12 and in the East Dorset on the 16^th. Two northern mockingbirds were seen in Windham on the 15th.

You can explore all the birds reported in Vermont and add your own sightings at Vermont eBird.

Kent McFarland