Are squirrels’ nests used by any animals or birds in the winter? Do squirrels use the same nest more than once? Would like very much to see some information about that, in the paper! Thank you.

– Carol Anderson, Brunswick

With leaves off our deciduous trees, you’ve probably spotted some squirrel nests lately. Unlike birds, which only use their nests for raising their young, squirrels will use them throughout the year and for several purposes. Females raise their pups in a nest through the spring, but squirrels put the most effort into building nests for the winter, which will provide them with a well-insulated structure to help survive the cold temperatures. Nests are also used for storing food, which is especially important in the winter when a snowstorm could bury most of the food a squirrel would need.

Ambitious squirrels will make multiple nests, and there are multiple types they can occupy. Some squirrels are secondary-cavity nesters, which you can think of as similar to a bluebird, where they use an abandoned cavity previously excavated by a woodpecker or other primary-cavity nester. Most of these cavities are in trees, but sometimes they’ll move into other structures (even houses) and you’ll often see squirrels take over birdhouses by gnawing the openings large enough for them to enter. The more commonly encountered squirrel nest, better known as a drey, is the large messy stick-and-leaf nests that you’ll see high up in trees. These dreys are constructed entirely by the squirrels themselves and with regular upkeep can last for years.

To answer Carol’s question: squirrels keep using their nests, but few others will find them useful. I wouldn’t be surprised to learn that other smaller rodents may use abandoned dreys to cache food in the winter – a common thing for field mice to do with old bird nests. Other mammals, like raccoons, would have a competitive edge in taking over a cavity for the winter. I have seen a variety of birds, from wrens to woodpeckers, picking through vacant dreys, presumably finding old seeds or various insects that were also using it for shelter.

BEST NOT TO HANDLE BATS YOURSELF

Sometime in early December, a little brown bat decided to hang around upside down in my small enclosed porch. It seems it may have decided to hibernate, because it hasn’t moved in a few days. The porch is insulated but will likely drop below freezing on many of the coldest nights. It’s only dimly lit by a streetlight and not used all winter. I hesitate to disturb it and interrupt its slowed metabolism, but I also worry whether it would be safe there long term. Any suggestions?

– Jenifer Ambler, Sebec

Maine’s bats, especially the ones that stay here and hibernate through the winter, need all the help they can get. While three species of Maine’s bats migrate south, those that stay, including little brown bats, have seen their populations decline by 97 percent because of white-nose syndrome, a fungus that causes them to rouse from hibernation. It is quite common for Maine homeowners to encounter bats that have found their way inside of a house, so I hope I can offer some advice to find resolutions that end well for both the bats and the homeowners.

In many cases, like Jenifer’s, the best thing to do is leave the bat alone until spring. By this late date, any bat you see is well into its hibernation and would not have an opportunity to find food, should it wake up, as there are no flying insects in winter. Studies have found bats lose 2 to 3 percent of their body fat during each arousal, and these do happen naturally (everybody poops), but additional arousals from human disturbance could be the proverbial straw that breaks the camel’s back.

I always recommend contacting a professional before you make any decisions about how to handle bats. I mean that figuratively and literally! Don’t handle bats, certainly without some heavy-duty, preferably leather, gloves. Jenifer’s bat may need help given the potential low temperatures in the enclosed porch she mentioned, though its chances of survival are better where it is than being roused and moved outside. (Our brown bats typically hibernate in caves where they can tolerate the cold, but prefer above-freezing temperatures.) Maine does have great wildlife rehabilitators that are trained and licensed to help if needed. Never care for wildlife yourself.

If you do have bats inside your house, in an area where they are not wanted, use the winter to come up with an exclusion plan for the spring. You want to find where the bats got in, and set up a one-way exclusion device that will allow the bats to leave when it warms up in the spring, but not be able to come back inside the house. Putting up bat houses will help give them a spot to move into, and my best advice is to “go big!” Most of the bat houses I see installed are too small to be preferred by these communal bats.

Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about virtual and backyard birding, online classes and other programs about wildlife and habitat.