Nature Watch: Bat Weather
About the author: Steve Ellis is a naturalist and Land Trust member who enjoys sharing his love of the natural world. His blog series, “Nature Watch,” will appear each month in “Habitchat,” chronicling native plants and wildlife you can expect to see during that particular time of year. We thank Steve for sharing his passion, illustrating the importance of island conservation.
August means bat weather. Hot summer days followed by warm evenings produce abundant insects. At least five bat species take to the air in our area: California, Yuma and little brown myotis, along with Townsend’s big-eared bat and silver-haired bat.
Most foraging flights are done right after dusk and again just before dawn. Bats often rest in the middle of the night to allow time for digestion after their initial feeding frenzy.
Bat numbers peak by the first of August. Once weaned, pups born this year are out chasing prey on their own. By month’s end, the bat population may drop, with some individuals migrating near to their hibernation spots.
People with keen hearing can hear the calls of bats or the dry rustling of their wings. These calls shouldn’t be confused with echolocation—the sound waves bats emit to track down prey and avoid colliding with objects in the dark.
It’s nearly impossible to identify bats in the air, the exception being the bi-colored big brown bat. Only equipment capable of detecting the echolocation calls can distinguish one species from another. Experts can identify bats when hand-held, but those of us who aren’t experts are warned never to handle a bat because of the remote chance of rabies.
Flora: Fireweed (Chamerion angustifolium)
Fireweed is a showy perennial that can grow to a height of five feet. The numerous leaves, growing directly from the stem, are lance-shaped and measure two to five inches in length.
Four-petaled pink to magenta flowers are clustered in a spike above the leaves. Seed pods form, each with 300 to 500 seeds (a single plant may produce 80,000 fluffy seeds!). The pods split, allowing wind to scatter the white fluff.
It would be difficult to find a species of bee that isn’t attracted to the nectar found in fireweed blooms. Deer, rabbits and muskrats also browse the plants.
Fireweed’s most important ecological role is that of stabilizing soils. Their root systems can reach a depth of 17 feet. After a wildfire, fireweed quickly colonizes exposed ground, anchoring the soil and allowing other flora such as red alder to gain a foothold.
Fauna: California Myotis (Myotis californius)
California myotis is one of our smallest bat species, reaching a length of three and three-fourths inches, of which one-third is the tail. They are rusty to dark brown in color and have a wingspan of nine inches.
Daytime roosts for this species are behind bark on snags and similar habitat. They emerge after dusk and may forage until dawn. Peak feeding comes in two periods, late evening and again in early morning. Prey items include moths, beetles and flies.
Flight pattern is a clue to possible identification. Their flight is comparatively slow but highly maneuverable as they chase after concentrations of small insects detected at close range. Frequent abrupt alterations of direction are hallmarks of California myotis.
Watch for these and the other two lookalike myotis species in forest openings and where trails and roads cut through the woods.