Bat Houses and Placement Strategies

I have invested a fair amount of time researching bats the last month or so trying to learn more about the fascinating creatures sharing my yard this summer.

After last week’s blog about my recent success with bats a few customers had questions.

One customer asked “why do you think you have more bats this year. What did you do to encourage them”? The fact is I’ve done nothing different and I wish I knew why we have this surge in numbers. The bat house has been in the same place for several years. The only thing about the “Rocket” style house that’s different is Downy woodpeckers have pecked a couple of holes in it ranging in size from about 1 ½” to 3” in diameter. I hardly think that would increase the chances of a box being used.

Bats have to find new roosts on their own. They investigate new roosting opportunities while foraging at night, and they are expert at detecting crevices, cracks, and nooks and crannies that offer shelter from the elements and predators. Bats are not blind as the saying goes but in fact have sharp eye sight.

BCI (Bat Conservation International) indicates 90 percent of occupied bat houses were used within two years (with 50 percent occupancy in the first year). The rest needed three to five years for bats to move in. So, perhaps it was just time needed for bats to locate my house. Now that I’ve attracted bats to this house I am planning on putting up at least one more before next spring.

There's a lot of information about success rates of various types of bat houses and, perhaps more importantly, how they are presented. I am merely going to summarize some of the more pertinent information and would encourage you to visit www.batcon.org if you want to learn more or have enough interest to construct, or buy, a bat house to install in your yard.

Below are some basics of presenting a bat house.

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Three chamber bat house.

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Rocket style bat house.

Facts, Tips and Suggestions

Bat houses installed on buildings or poles are easier for bats to locate, have greater occupancy rates and are occupied two and a half times faster than those mounted on trees.

Tall designs like the multi-chamber (nursery) and rocket-style houses perform best

Occupancy in rural areas is over 60 percent, compared to 50 percent for urban and suburban areas.

According to BCI maintaining proper roost temperatures is probably the single most important factor for a successful bat house. They say interior temperatures should be warm and as stable as possible (ideally 80º F to 100º F in summer) for mother bats to raise their young. Some species, such as the Big Brown bat, prefer temperatures below 95º F, while others, such as the Little Brown bat, tolerate temperatures in excess of 100º F. This is very interesting because we always think of bats in relation to the coolness of caves but this is mostly during the hibernation months, fall through winter.

Bat house temperatures are influenced directly by the exterior color and direction faced. East-, southeast-, or south-facing are generally good bets. My Rocket house is, as you have seen, a darker color. Bat houses we sell are almost always a plain western cedar. From now on I will suggest staining the box a darker color.

Avoid placing bat houses directly above windows, doors, decks or walkways. Bat urine and guano would fall directly down to whatever is below. The urine is known to stain some finishes.

For more information about constructing, painting, installing and maintaining your bat house, please see:

The Bat House Builder's Handbook

Single chamber bat house plans

Four-chamber nursery house plans

Rocket box bat house plans

My Summer Bats

Bats have been of particular interest to me this summer as I’ve had great success with a “Rocket” style bat house. This box has been on a 10’ post in my yard for several years and seen only minimal success.

Most evenings my wife and I settle in to watch the bats emerge from the box which is situated in a clearing surrounded by trees. We’ve been able to count over one hundred several times. Only recently have I come to the conclusion they are the species, the Little Brown Bat, perhaps the most common, widely distributed in the U.S. They measure less than 4” in length and vary in color from olive-brown to a yellow-brown. The wings consist of naked skin, which are attached alongside the feet.

There are several bat species that are very similar in appearance, so we are still observing for more details and clues that will help definitively identify them.

During summer Little Browns often inhabit buildings, usually in hot environments like attics, where females form nursing colonies of hundreds or even thousands of individuals. Not much is known about where the males are at this time but they are likely solitary and scattered in a variety of roost situations. Colonies are often close to a lake or stream. This species seems to prefer to forage over water, but also forages among trees in open areas. Little Browns may repeat a set hunting pattern around houses or trees. Little Brown bats eat a variety of insects, including gnats, crane flies, beetles, wasps, and moths. Here is a very interesting thing I did not know about bats. Insects are usually captured with a wing tip, transferred into a scoop formed by the forwardly curled tail, and then grasped with the teeth. Because we don’t get to see them working in slow motion we would never see this action.

After doing a little more research on Southeastern bats, I learned some very interesting facts about these fascinating little nocturnal mammals. For instance, did you know that at certain times of the year we can have up to fifteen different species of bats in the southeastern United States? Or that all bats in the eastern United States feed exclusively on insects? They are the only major predator of night flying insects and may eat more than 50% of their body weight each night. Unfortunately, the amount of mosquitos they consume is not as great as once thought.

In late fall and winter the Little Brown Bat usually hibernates in caves and mines. Bats return from migration and awaken from hibernation as early as mid-March and they will be abundant throughout the summer and into early fall. By mid-October most will have migrated to more southerly states, or are going into hibernation. For more information about bats in our area please visit: www.tnbwg.org the Tennessee Bat Working Group website.

Where are the Goldfinches?

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We field this question a lot this time of year. Goldfinches are quite different than many of our other feeder birds in that they are frequently on the move. Goldfinches you see for a few days or a week may be miles away tomorrow only to be replaced by a new group shortly thereafter. These movements are even more prominent in the spring. We tend to see more Goldfinches concentrated at feeders in winter as northern populations move south. With migration all but over here in mid-TN we should begin to see good numbers of Goldfinches settling back in to bird feeding stations. So, don’t think that you’ve done something wrong, or think the seed in your feeder is bad, it is normal for Goldfinches to be on the move. Here are a few tips to improve your success with Goldfinches.

Ø Keep your feeders full. Goldfinches prefer to feed as a group and will not find a feeder attractive if it only has one feeder port available to feed from. Top them off regularly.

Ø Check your seed for dampness particularly after rain showers. Simply shake your feeder up and down to see if the seed is dry and loose, or gotten wet and clumped together. Remove only the wet seed. The Aspects brand Quick Clean feeders are a great choice of finch feeders for easy maintenance and cleaning.

Ø Keep feeders clean. Mold is a bad thing to have on your feeders and seed. Really dirty feeders can be detrimental to the birds and be a source for spreading disease. Not to mention making them less desirable. Keep in mind Goldfinches are totally vegetarian. They do not eat insects. So with lots of seed choices available in nature the seed at your feeder better be in tip top condition to compete.

Ø If you have multiple finch feeders we recommend grouping them. Again, they prefer to feed as a group, so it pays to give them that opportunity. The more the merrier.

Goldfinches love sunflower whether in shell or out. Check out our Finch Blend which is Nyjer seed and Fine Sunflower Chips, and the Fine Sunflower Chips which can be used in any finch feeder.Be advised, if using the Finch Blend or Fine Sunflower it is recommended you present the feeder in a squirrel proof manner, like a baffled pole system, for example.

Ornithology Vocabulary Lesson.

Since we are in the breeding season for birds here are a couple of ornithology words to expand your knowledge. They may even help you with the next NY Times Crossword.

Altricial and Precocial

Almost all of us have seen baby songbirds in a nest.We know they are completely dependent on the adults to keep them warm as they are featherless for the first few days and to bring them food while in the nest developing.They are completely helpless and mostly immobile.The adults continue to feed them for weeks even after they have fledged. This is referred to as altricial. Altricial birds include herons, hawks, owls, and most songbirds.

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Eastern Blue bird babies just hatched. No feathers and eyes still closed.

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Day 12 birds are fully feathered and still being fed. They will leave the nest any day.

Precocial means young are capable of a high degree of independent activity immediately after hatching. Precocial young typically can move about, have their eyes open and will be covered in down at hatching. They are generally able to walk away from the nest as soon as they have dried off. They will also begin searching for their own food. Examples of precocial birds include most duck species, Wild Turkey, Quail, and Killdeer.

Spring and Summer Bird feeding Challenges

It’s most definitely upon us. The time of year when many of you are faced with challenges certain backyard visitors present. They can really test ones patience. I’m talking about Grackles and Starlings, Raccoons, Chipmunks, and Ring-tailed Lemurs. Well, maybe not Ring-tailed Lemurs.

Your bird feeders are of great interest to all these birds and animals largely due to the breeding season. I did not mention squirrels because we deal with them every day. The others are more of a seasonal issue. One thing worth mentioning about squirrels is they are more likely to eat safflower during this time. We’ve already heard from a few of you that squirrels have decided to start eating safflower when previously they did not. Usually it’s the young squirrels that eat safflower. This too shall pass.

When Grackles and Starlings are on the nest they seek quick, easy food sources and will visit in droves, eventually bringing their babies, too. We recommend a variety of strategies to lessen their impact:

· Offer nothing but Safflower seed rather than sunflower or blends with shelled seeds, shelled peanuts, and fruit. Safflower is smaller than sunflower and has a different shape, and a hard shell that Grackles and Starlings cannot crack open.

· Limit opportunities, and opportunities available should be difficult for a large bird like a grackle to use. For instance, small bird only or caged type feeders. Yes, this will also limit Cardinals but they would be happy to feed on whatever falls to the ground. If you have a tube type feeder with straight perches consider cutting them in half. They are usually made of aluminum and easy to cut. Half a perch will present great difficulties for a Grackle and Starling but small birds will use them easily.

· We also suggest shutting down feeders for a while, perhaps a week or two. This can cause these sudden intruders to move along to find a reliable food source. Usually the Grackle/Starling pressure recedes by mid to late June when breeding is concluding. Birds you like to see will typically return to feeders in little time.

· Suet is a favorite food source during this time because it’s soft and easy to take large chunks. Again, removing the food source for a week may cause the problems to move along. Another thing to try is take note of the timing of their visits. You can offer smaller amounts of food, like a third of a suet cake at a time, so your desired visitors have a consistent food source for part of the day. When the problem visitors show up there is little food remaining.

· Squirrel proof suet feeders are very effective at keeping squirrels out but not always the Grackles. Only the largest Squirrel proof suet feeders provide enough distance between the food source and the outer cage to stop Grackles and Starlings.

Next to Grackles and Starlings there’s a tie for most complaints between Raccoons and Chipmunks. Raccoons are expert climbers, they have great dexterity in their paws, which are really like hands, they can grow to be quite large, and their strength and brain power far exceeds that of a squirrel. Many of you find your feeders on the ground in the mornings damaged with squirrels gathered round feasting on the exposed seed. This is a sure sign that a raccoon has been “working the night shift” as they are mostly nocturnal. They will take feeders off hooks and hangers with ease, take the lids off and eat until they are satisfied, and leave the scraps for the squirrels. Here are some suggestions for reducing raccoon problems:

· Bring feeders in at night that are accessible to raccoons. It may take a few weeks to condition the raccoon to not to show up. After a few weeks try leaving a feeder out one night to see if they have gotten the idea that no food would be available. Continue taking the feeder in if you see evidence they’ve been there.

· The “limited amount” strategy works well here, too. If it’s suet they are getting put only a third or half a cake in the feeder. By nightfall when the raccoon shows up there would be little if anything left.

· Raccoon baffles for pole systems, which are much larger than squirrel baffles, are very effective. Follow directions and you will have success. A squirrel baffle will not likely stop a motivated raccoon.

· This is not my favorite strategy but some people will make food available in places away from feeders. They might offer table scraps, corn, or cat food to satisfy the raccoons. I see evidence of raccoons getting in my compost pile where I put everything from coffee grounds to old fruit and vegetable scraps. In my opinion this strategy just encourages their desire to visit.

Chipmunks are challenging in that they can squeeze through caged squirrel proof feeders and they are not heavy enough to activate most weight activated feeders. And they like safflower. However, any squirrel baffle used properly will stop them cold.

Be patient. We need to try and be tolerant of all wildlife even when they are pesky.

House Wren Competition

After our blog about “dealing with predators and problems” appeared last week we received a couple of comments about House Wrens (HW). One comment referred to the HW as a predator. Technically the HW is not a predator but a competitor, and has been known to pierce eggs and even kill baby birds in the nest box. They also have the unique behavior of filling up several available boxes with their nest material with no intention of using those nests. These are known as “dummy nests”. This is an interesting dilemma because the HW is a native songbird and must be treated as such.

The House Wren is not a year round species, like the Carolina Wren, and tends to first appear in this area around mid-April. They are fairly common but many of you will never see one in your yard. In 28 years at my home I have never included the House Wren on my “yard bird” list.

HW’s use almost exclusively sticks for nest building so when monitoring your nest boxes this is an easily identified nest. Any advice we can offer to help keep HW’s from doing what they do may “backfire”. Offering more choices of nest boxes can alleviate “pressure” on the one or two already present but may encourage more HW activity. Spending a little time monitoring your boxes can help. For instance, if you find sticks in a nest box where Bluebirds have been building a nest you may remove the sticks. Don’t just drop them on the ground because HW’s will just retrieve them and put them back. Or as we suggest with House Sparrows plug the entrance hole to a box for a while if you see HW activity.

An interesting strategy to try if you have experienced HW issues is the wren guard. The wren guard disguises the entrance hole. (Click here for a more in depth look at the wren guard). The wren guard is best used after a Chickadee or Bluebird, for example, have already fully committed to a nest by laying eggs.

It’s good to remember competition among birds for nest sites can reveal some difficult things about nature.

We hope this helps some of you and next week we will spend a little more time on monitoring Bluebird boxes. Please keep the questions coming. We enjoy being able to address things you want to learn about backyard birds.