Sunday, January 13, 2008
Silver-haired bats in Patrick County
Dr. Eric Johnson, a retired ornithologist who lives near Stuart, found a silver-haired bat in his home. This is the second time he's caught one of these critters and released it outside.
Bat Conservation International says that Lasionycteris noctivagans is one of the most common bats in forested areas in North America. I'm no bat expert, but it's not a species I'm aware of having seen myself. The most common bats I encounter in our area are the little brown bat and the red bat.
The silver-hair is associated with coniferous and mixed coniferous/deciduous forests. BCI says they are dependent on old-growth forests, and for that reason the maintenence of forest corridors is important to this species.
Read about the relationship between forest-dwelling bats and old-growth forest at this link.
A friend of mine who knows this species tells me that one way to tell a silver-haired from other species in the half-light of dusk is the marked slowness of its flight compared to other bats, such as the little brown bat. The silver-hair, he says, "dawdles around" in the air.
The range maps for the silver-haired may be misleading, because over big parts of its nominal range it is present only during the spring and fall migrations. Dr. Johnson says that, as far as he's concerned, finding two in his house, on both occasions during winter, settles the question for him of whether or not they're in our part of the southern Appalachians this time of year.
Like many birds, the silver-haired bat is good at getting home again. One individual traveled 107 miles back to its home roost after migration.
Red-tailed hawks are known to predate bats in some areas, especially out west, especially at dusk, as the bats pour out of caves to feed for the night. And why not? They're basically flying mice. I found myself wondering if redtails in the southern Appalachians feed on bats to any significant degree. The overlap between a redtail's normal hunting hours and those of crepuscular species like bats is brief. Does anybody have good data on this?