If you slow down a bat call by about 10 times, it sounds a lot like a 'tweet'...

I concur with Sarah that what Mike saw was likely a Big Brown or a Silver-haired
bat, but my reasons are a little different.

Contrary to long-held belief, several species of bats in the Puget Sound region
are indeed active throughout winter. Most species no doubt go off to somewhere
colder to hibernate, or as mentioned in other posts, the Hoary bats head way
south, and don't appear to hibernate.

I've been monitoring/recording winter behavior of bats in the So. Puget Sound
area (with bat detectors) for about 4 years. Silver-haired bats and California
myotis bats are out and about -- and feeding -- on just about any mild winter
evening. The formula appears to be: Not raining & daytime temperature above 50F.
Also, location. Around Olympia, I hear them active mostly around farms, parks, &
woodland edges, but not pods and lakes. On cold evenings, like we've been having
recently, they might be active for less than an hour after sunset, but on one
mild evening on 21 Nov. 2005, I heard a couple Silver-haired bats 'working' the
area around Priest Pt. Park after 11 pm.

There have been a few reports of Big Brown bats roosting during the winter in
fairly unprotected spots here around Olympia, including a lone one that I've
been watching that is roosting under a bridge for the past couple of months. The
temperatures in the Puget Sound lowlands are probably not cold enough for bats
to actually hibernate as they do in caves and mines, obligating them to go out
and feed when possible. They certainly use torpor to save energy when its cold
or wet, just as they do in the summer during bad weather, but these bats are
actually out 'flying their routes' and feeding (they make a district call when
approaching prey, nicknamed 'feeding buzz').

So, the crane fly behavior that Rob Sandelin described in his post might help
explain what they are feeding on, especially since both of the species I
regularly 'hear' during the winter tend to forage near forest edges... and 40F
seems to be about the temperature when things go quiet. I've found that some of
the many species of midge hatch throughout the winter, especially after a short
bump up in temperature.

The documentation can be found in a paper in NW Naturalist, "Winter foraging
behavior..." linked here:
<http://www.cascadiaresearch.org/reports/Bats-NWNaturalist-2007.pdf>

By the way, we don't <yet> know where most of the bats that leave this area for
the winter are hibernating.

-Greg

--
Greg Falxa
Olympia, Wa.
gregf <at> efn.org

> [Tweeters] RE: A bat!
> Sarah Schmidt junco at galaxynet.com
> Tue Feb 3 20:35:25 PST 2009
>
> [I sent this earlier this evening and all that showed on the Tweeters List was the subject line and my name, but not my message. I'm trying again!]
>
> Another possible reason for a bat to fly in mid-winter is to get a drink. In some cases during hibernation, dehydration may be more of a concern for them than starvation.
>
> My understanding is that hoary bats migrate well south of here for the winter, but I believe silver-haired bats commonly hibernate in the area through the winter. I'm aware of a number of instances of people coming across silver-haired bats in hibernation in western Washington, on more than one occasion in a woodpile. I found one on a house wall behind a bat box.
>
> The bat Mike saw was most likely a Big Brown, which can appear surprisingly large in flight.
>
> Sarah Schmidt
> Coupeville
>
> --
> ^o^ ^o^ ^o^ ^o^
> Sarah Schmidt
> TERRAFILIA
> 243 Rhodena Drive
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