Walker Nature Center
A look inside • Calendar of Events 4 • Kids’ Corner 6 • Bluebird Box Monitoring 7
Branching Out
Nature Notes
Chickadee Economics
December
Thermoregulation is a big word. For animals in winter it can also be a big problem. As winter produces the lowest temperatures of the year, wildlife must find ways to cope with these extremes. Surprisingly, endothermic (“warm-blooded”) animals have more of a challenge during cold weather than their ectothermic (“cold-blooded”) counterparts. The challenge for a small bird or mammal in cold weather is to mitigate heat loss, either by finding ways to reduce it or by consuming more food. Carolina Chickadees are small birds. An adult weighs around one-third of an ounce (10.5 grams), or just less than two quarters. Their surface area to volume ratio is high, so they are more prone to heat loss. Imagine heating up two metal balls, one the size of a golf ball (a chickadee) and another the size of a bowling ball (a hawk). If, after heating, you had to choose which metal ball to touch first you would probably choose the smaller, golf ball-sized one, expecting it would cool off first. The same is true for animals. Smaller birds like chickadees are prone to greater heat loss than larger birds like hawks or turkeys.
By Sharon Gurtz
• • • •
Waterfowl populations peak. Woodchucks hibernate. Foxes begin searching for mates. Juncos have arrived from the north.
January
• Great Horned Owls begin breeding. • Sparrows forage in flocks. • Deer shed antlers. • Raccoons breed.
February
• Chipmunks emerge from their winter dens and breed. • Striped Skunks breed. • Spring Peepers start to call.
By Ken Rosenthal
Birds of a Feather
Feathers are terrific insulators, better even than the hair of mammals. Birds in winter can fluff up their outer feathers, trapping warm air in pockets against their skin. Most heat loss for a chickadee will occur around the eyes and beak. While sleeping they tuck their head under their scapular (shoulder) feathers to conserve heat. The preferred shelter of Carolina Chickadees is a tree cavity. They use them for nesting and for roosting during cold winter nights. The cavity may be a small one they hollow out themselves, or a larger one that was made by another bird, such as a woodpecker. Carolina Chickadees flock together during winter, often forming mixed flocks that can include Tufted Titmouses, Downy Woodpeckers, kinglets, warblers, and Brown Creepers. These birds also compete with chickadees for roosting cavities. However, the additional eyes for spotting food and danger outweigh the negatives of roosting competition.
Winter 13-14 Volume Sixteen