Bat House Forum

[LarryH]

I have to replace the night light mounted up on the end of my garage, and the electrician suggested I replace it with a new Metal Halide light with the photo sensor. The bats have gone home for the winter already, but I want to prepare for them next year. Will the bats hunt for bugs under Metal Halide lights like they do with older white mercury vapor lights? Or, are there better lights for the bats benefit?

[Joe Spencer]

If the light is whiter and brighter it attracts more insects. Sodium lights which have a orange yellow hue do not attract as many insects. Metal Halide gives off bright white and therefore attract many insects.

[LarryH]

Thanks, Joe! That is what I was looking for. The old mercury vapor light is a white light, but not bright white. In the nearby town they are replacing all the street lights with ones that give off a yellow glow in the hopes of limiting bugs on the streets, and I didn't want that kind of light I think I'll tell him to go ahead with the Metal Halide that he proposed -- he recommended a Pulse Start light which he says has over twice the lifespan, but it supposed to also be a brighter white.

The bats left earlier this year than ever before, and I hope that doesn't mean we're in for an early winter.

[Joe Spencer]

Also the bats do take occasional dips below the lights to forage however most of the feeding is done just above the lights in the darkness. At Texas rangers stadium thousands of bats feed nightly during their night games when the lights are on and many bats are seen below the lights but many more are feeding just above devouring insects.

[Dave Miller]

It would be interesting to compare the ultrasonic noise produced by various types of street lights, using a bat detector. I would think that bats might avoid particularly noisy lights. If you have a bat detector it is fascinating to walk around the neighborhood to see what produces ultrasonic noise. One of the noisiest spots I found was underground in the middle of the street. Apparently when water goes through a constriction, it makes a lot of ultrasonic noise. So I was hearing buried water pipes. But most electrical/electronic things make a lot of noise as well.

Hey I just had a thought - next time I go to Home Depot I'll bring my bat detector to their lighting display and see which type of light makes the most noise. Hopefully their security people will not tackle me thinking I am some kind of loony or terrorist.

Here's a related article I just now ran across: Noise pollution threatens animals

[Erik]

Hi Dave,

just curious : are you using a frequency division detector or a heterodyne one?
I have also noticed that some streetlights produce ultrasonic noise, especially new energy saving lights. I have no information about types though.
About the noise from underground waterpipes. Runnig water produces a lot of ultrasonic noise, but I have also encountered new high pressure sewer systems where the system produces a constant high pitch tone between 40 and 50 Khz. And that is within the frequency range of a lot of Vespertilionidae-bats.

greetings,
Erik

[Dave Miller]

Hi Dave,

just curious : are you using a frequency division detector or a heterodyne one?

Frequency division. It is the "Simple Bat Detector" from Tony Messina. Nothing fancy but it meets my needs.

[LarryH]

I got the new Metal Halide light put up yesterday, and I love it! It is a bright white, versus the blue white of the old Mercury Vapor light. The bats were frequently seen around the night light, and I can't wait until next year when they return to the houses to see how they like the new light. I suspect that the bright white light will attract more insects, and thus be of more of interest to the bats.

The old light had developed a noticeable buzzing sound when it was on, but the new one is totally quiet. The buzz of the old light may have been due to the ballast going bad, though.

[Joe Spencer]

Great! Save some of that guano for me will ya Larry! LOL

[LarryH]

You'll have to pick it up, Joe! Ha!

Last year, I planted Crimson Clover under the bat houses so I wouldn't have to mow under them, and it has worked out really well. Not only is the crimson clover beautiful and eliminates the need to mow, but it seems to love all the guano that falls to the ground. After the bats left this fall, I mowed the clover and reseeded it to get another strong stand next year. The seed store recommended that i put limestone on it, so I may do that before winter sets in as well.

I think a side effect of the clover is that it would offer proection to any young bats that fall from the houses. I don't know that is the case, but it seems that it would.