I’ve done a little reading recently and, believe it or not, it’s time for bat migration to begin. What I’ve found is that a sub-culture of nature enthusiasts exists that spend much of their time studying and caring about bat populations. Everything from migration to habits to specific bat diseases are studied.

Interestingly, wild bird store owners “dabble” in things having to do with bats. I know that, in my store, we dealt mostly with the occasional customer interested in purchasing a bat house. Bats also enjoyed a certain popularity in the Fall, thanks to Halloween.

Some species will hibernate in winter if they can find a suitable spot. These bats in Northern climes will usually come out of hibernation in April. According to the USGS, Forty-five bat species inhabit the United States, and many make short-distance movements between summer and winter quarters. However, four of these species may have longer migratory pathways than any other terrestrial mammal in the Northern Hemisphere. These four species, commonly referred to as “tree bats” because they roost in the foliage or trunks of trees, are hoary bats (Lasiurus cinereus), eastern and western red bats (L. borealis and L. blossevillii, respectively), and silver-haired bats (Lasionycteris noctivagans).

Further, what they have found is that it has been difficult to understand and track the migration patterns of these bats because, unlike birds, they are not often seen and few attempts have been made to follow their travel over great distances. Some studies have shown that, whereas birds migrate in search of better food sources, bats typically migrate with the intention of finding better hibernation conditions. Since they typically “roost” in trees, as temperatures drop, they likely will travel to slightly warmer climates.

Bats and Wind Turbines

Dead bats are turning up beneath wind turbines all over the world. Bat fatalities have now been documented at nearly every wind facility in North America where adequate surveys for bats have been conducted, and several of these sites are estimated to cause the deaths of thousands of bats per year. This unanticipated and unprecedented problem for bats has moved to the forefront of conservation and management efforts directed toward this poorly understood group of mammals. The mystery of why bats die at turbine sites remains unsolved. Is it a simple case of flying in the wrong place at the wrong time? Are bats attracted to the spinning turbine blades? Why are so many bats colliding with turbines compared to their infrequent crashes with other tall, human-made structures?

Although these questions remain unanswered, potential clues can be found in the patterns of fatalities. Foremost, the majority of bats killed by wind turbines are species that rely on trees as roosts throughout the year and migrate long distances; we call these species “migratory tree bats.” Currently, migratory tree bats compose more than three quarters of the bat fatalities observed at wind energy sites. The other striking pattern is that the vast majority of bat fatalities at wind turbines occur during late summer and autumn. This seasonal peak in fatalities coincides with periods of both autumn migration and mating behavior of tree bats. Seasonal involvement of species with shared behaviors indicates that behavior plays a key role in the susceptibility of bats to wind turbines, and that migratory tree bats might actually be attracted to wind turbines.

Bats and Your Backyard

Now is the best time to install a new bat house for possible colonization this year. The Organization for Bat Conservation says that bat houses are still important. Bat houses benefit bats, you, your family, communities, farmers, gardeners and the ecosystem as a whole.

• Bat houses give bats a home and in turn they will eat thousands of insects.
• Bat houses give bats an alternative to our houses thus reducing the chance of human to bat contact.
• Bat populations have decreased significantly (especially with WNS) and bat houses can help provide secure habitat.

Bat houses provide a safe home for bats and are educational and fun for the whole family. Bats significantly reduce the amount of pest insects in your backyard while simultaneously helping farmers and gardeners by eating insect pests. An individual bat can eat thousands of insects in just one night! More bats eating insects mean less pesticide use in our environment.

A general rule of thumb in terms of house placement includes:

• At least 15 feet off the ground, if possible
• Facing southwest to gain exposure to sunlight
• Free from obstruction, including below the house (for example, not in a tree with branches below)

Studies have shown that houses placed on a pole or structure are more readily occupied than those on a tree. Also, the more chambers a house has, the greater a chance it will become colonized. Bats will usually move in during the first year. If there is no activity by the end of the second summer, it might be a good idea to move the house to another location. If a house is painted, one should use a non-toxic water-based paint.

Guano Specific … Really?

I had heard that colonies of bats were scent specific and that use of guano in or near a new house might be a deterrent to its becoming inhabited.  In actuality, absolutely no research has been done as to whether bats will or won’t be attracted by placing purchased guano on or near a bat house. One thought – and this is only a thought – is that it may be possible that bats may not want to move into a house that bears the scent of another colony. Not to mention the fact that purchased guano is likely from a different breed of bat all together.

There is one situation in which guano might be useful. That would be if one has bats in one’s house or attic and would like to entice them to relocate into a new house. In this case, placing some guano from an area where they have been inhabiting might make them smell something familiar.

Sources:

http://www.fort.usgs.gov

http://www.batconservation.org/drupal/