Headlines - Region 4
понедельник, марта 30, 2009
What do migratory songbirds do when they arrive in Montana in early spring and find ice, snowdrifts and wind chills below freezing?
Some die, of course, but many songbird species here now have evolved over time to survive later winter storms.
"Robins that had started to disperse to nesting areas go back into winter flocks," says Graham Taylor, Fish, Wildlife and Parks regional wildlife manager.
Bird behavior, like migration and nesting, is tied to daylight length more than weather. For early spring migrants that occasionally means arriving at nesting areas only to find winter lingering.
When that happens, Taylor says, "they’ll find micro climates that are warmer and provide food. In north central Montana that’s often around the rivers."
Around open water in the Missouri River, for example, it can be warmer or at least out of the wind and hold insect life, which means food.
Other migratory birds that arrive annually by the end of March, like bluebirds, red-winged blackbirds and western meadowlarks, have similar strategies that allow them to survive brief bouts of winter. Sometimes it’s just a matter of hunkering down.
"Sometimes those birds, like waterfowl, will have places where they stop over, awaiting a break in the weather," Taylor says.
"What you don’t see now are the warblers," Taylor says.
Birds like orioles and yellow warblers are still far to the south. Typically they arrive in mid-May, or later. Those birds have evolutionary strategies that allow them to stay in wintering grounds longer, arrive up north later and survive.
So it may not look like spring outside now, but to some birds spring has arrived.