The Silver-Haired Bat, and I’m Not Talking About Your Grandmother!
I’ve been spending the week on a work site performing wetland delineation for the purpose of altering wetlands to reduce the chances for Bird/Animal Aircraft Strike Hazard (BASH), Bird Avoidance Model (BAM). I will then design wetland modification and mitigation to reduce waterfowl near runways.
A contractor brought in an injured silver-haired bat to the Natural Resource Management Office, on base at Patuxent Naval Air Station, where our temporary office was located. The following are a couple of photos of the bat, which has an injured wing, and will be taken to a rehabilitator, and hopefully released soon, so that it can continue its winter migration to points south.
Silver-haired bats are relatively common bats in forested areas of America, most closely associated with expansive old growth (over mature) evergreen and hardwood forests. They form maternity colonies almost exclusively in tree cavities or small hollows. Like other forest roosting bat species, the silver-haired bats may sometimes switch (rotate through) roosts throughout the maternity season (kind of like Hillary Clinton’s inane “It Takes A Village,” as your children belong the the State).
Because silver-hairs are dependent on old growth, maintaining some areas for over-maturity, is an important management strategy. It is estimated that these bats require standing snag densities of at least 20 dead snags per 50-acres, in order to promote a roosting colony.
Unlike many bat species, silver-hairs also appear to hibernate mainly in forested areas, though they may make long migrations from their summer forest to a winter forest site. Typical hibernation roosts for this species include tree hollows, beneath exfoliating bark, in wood piles and cliff faces. Occasionally silvers will hibernate in cave entrances, especially in northern regions of their range.
Like big brown bats, silvers have been documented to feed on many insects perceived as pest species to humans, and agriculture/forestry. Even though they are dependent on old growth, silvers primarily feed in disturbed areas, sometimes at tree-top level, but often in clearings, and along roadways and water courses. They will eat flies, midges, leaf-hoppers, moths, mosquitoes, beetles, crane-flies, lacewings, caddis-flies, ants, crickets and spiders.
The bat squeaked “good morning Mr. Burchick, my wing is hurt, and I need some rehab time and plenty of insects, as I have a high metabolism.” I conveyed the message to the handler. Silvers migrate. They spend the summer throughout most of the United States, but prefer to winter in the southeastern states (just like retired New Yorkers). Few winter records are available, and a complete understanding of winter migration is lacking. Some sex segregation may occur, where females like the northern states and bear young, with many males staying behind in more southern locales.
The flight pattern is a distinctive flutter, with frequent darts, twists and glides. They appear as slower in the air, compared to other species. During feeding maneuvers, the tail and wing membrane are used to capture and restrain prey, like a sail. Note the tail in the photo that can form a pouch-like compartment in flight. Once the insect is captured, the bat, on-the-wing, can bend its head, grasp the insect with its teeth and ingest. How cool is that!