Saturday, February 23, 2008
At 5 a.m. Thursday the thermometer on the porch registered 3 degrees. A fresh blanket of snow covered the ground; it crunched under my boots as I enjoyed a brief, brisk predawn walk in the woods. The moon, which had been fully eclipsed by the earth just hours earlier, had wandered across to the western sky. Winter’s grip Thursday was firm; spring seemed a distant promise.
But for some animals, the breeding season has already begun. Photo period is a more important and reliable environmental cue than temperature.
Male gray and fox squirrels, for example, began to vie for mates in late December, soon after days began getting longer. With occasional breaks for food and rest, males chase females for about two weeks. Eventually the female accepts the overtures of the most persistent male. Mating occurs in January.
Squirrel gestation is surprisingly long. Litters of two to five kits (average three) are born in a tree cavity lined with leaves about 45 days after mating. Most squirrel litters are born in mid-March. Another series of chases ensues in early June and leads to a second litter in July or early August.
Great horned owls and bald eagles also get a jump on spring.
Female great horns lay the first of two or three eggs in late January or early February. Three days later she lays another. If food is abundant, she may lay a third egg. Though the eggs are laid at three-day intervals, incubation begins immediately with the first egg. This is why we sometimes see photographs of owlets of several sizes in the same nest. The eldest sibling in a brood of three may be six days older than the youngest.
Incubation continues for 26 to 35 days; the first egg laid is the first to hatch. Because great horned owls nest so early, the nest often gets covered with a blanket of snow. Snow may also blanket the incubating parent, but its soft downy feathers keep the eggs warm and dry.
Nestling horned owls grow rapidly, but they remain in the nest for more than two months. That’s one reason the nesting season begins so early. Another is that by the time the young owls fledge, there are new litters of rodents and rabbits to hunt.
Bald eagles follow a similar pattern. Just last week I received a press release from the Ohio Department of Natural Resources reporting that several pairs of Ohio eagles had begun to incubate their clutches. The first pair began incubating Jan. 28. This clutch is expected to hatch around March 5. Young eagles remain in the nest for up to 90 days, so again an early start is necessary to give young eagles sufficient time to perfect hunting skills by summer’s end.
Among the more surprising early nesters are two members of the jay family.
Gray jays inhabit the transcontinental boreal forest and the Rocky Mountains. These bold jays frequent camp grounds and store food throughout the year. In late summer and fall, they cache perishable foods such as fruits and bits of carrion. So when they begin nesting in late winter while the ground is till snow covered, they have a stockpile of relatively fresh food. Unfortunately, global climate change has begun taking a toll on gray jay populations. Unusually warm fall conditions in some locations cause these larders to rot, so their late winter food supplies spoil.
Another Rocky Mountain early nester, Clark’s nutcracker, caches thousands of pine seeds each fall, usually on south facing slopes. These slopes thaw first in late winter enabling nutcrackers to have a dependable food supply when they begin nesting in late February.
Surprisingly, early breeding isn’t limited to warm-blooded creatures. As rising temperatures melt vernal woodland pools, wood frogs will emerge from hibernation and gather around the edges, where males will sing to attract females to mate. And a week or so later, spring peepers will do the same.
So don’t be fooled by falling snow and frigid weather. For some wildlife, spring has already sprung.
X Send questions and comments to Dr. Scott Shalaway, RD 5, Cameron, WV 26033 or via e-mail my Web site, http://scottshalaway.googlepages.com.