If you mount a nestbox on a tree, large wooden post, fence or telephone pole with no guard, be prepared to lose adults, eggs and nestlings to raccoons, snakes or cats. Just because you don't have predation the first year doesn't mean they are safe - e.g., sometimes it can take raccoons 3-4 years to find the location of a "Happy Meal."

Either a Stovepipe (Kingston) or PVC wobbling baffle will guard your nestbox against climbing predators like raccoons and cats. It will also deter squirrels, chipmunks, mice, and rats as long as they cannot otherwise jump to the box. The slicker the better. (Note: some raccoons can climb up a 4" diameter pipe, especially if they are really hungry.)

For snakes, space or distance are needed between the center pipe used for mounting the nestbox, and the surrounding baffle. This allows the snake to go up inside the baffle. On Purple Martin structures mounted on 3"x3" steel square tubing, you can use an elevated, inverted 38 gallon trash can as a baffle.

The Stovepipe guard also deters snakes. A small (4") diameter PVC one does not, as snakes (esp. Black Rat Snakes) may be able to coil around it, even when greased. Ron Kingston (the inventory of the Kingston baffle) recommends 1n 8" or larger diameter stovepipe.

Raccoons have been known to get around metal cone guards on poles, even those that are 36" in diameter. That size conical baffle may not stop snakes over 5 feet long, which thank goodness are not a problem in CT. Conical baffles are fairly easy to make and are good for nestboxes mounted on wooden posts. See more information on deterring cats and snakes.

A 4 foot wide flat square of hardware cloth also works, but it makes monitoring difficult, has sharp edges, and is expensive.

Another option is a Noel Guard which MAY (or may not) deter raccoons, cats and squirrels, but not snakes or medium sized avian predators. It is a little wire cage (1/2" hardware cloth) that goes over the nestbox entrance hole.

Hardware cloth is not fun to work with - it's stiff and cut edges are sharp, so be patient and careful.

I recommend mounting a nestbox on a metal pipe (EMT electrical conduit - 1/2" for light boxes, 3/4 - 1" for heavier boxes). I put a wine cork in the top of the pipe so water doesn't get in and freeze and split it. Some folks regularly grease EMT metal conduit poles with lithium-based automotive grease, or spray with Pledge (furniture polish) or Eureka Fluid Film to make it harder for critters to climb an unbaffled pole.

What does not work well, or is not recommended:

• Use of a Bird Guardian (a commercially available plastic tube inserted into the entrance hole or screwed onto the box exterior) would provide protection against reaching predators (not snakes). However, it makes feeding more difficult and is generally not well accepted by bluebirds. Trail monitors have found that few, if any, bluebirds will use a box with a Bird Guardian on it, and some even abandon nests with eggs when a Bird Guardian is placed on a box. The instructions now indicate that it should only be used on a well established nest, and to watch after installation to verify that it is accepted. It can also create problems when opening a front opening box.
• A thick hardware block placed over the entrance hole does NOT deter raccoons (or snakes). It may make it more difficult for avian predators to reach eggs.
• Two short perches right under the entrance hole do not protect eggs or nestlings from cats or birds, according to Keith Kridler.
• Suggestions like wrapping a pole in barbed wire, putting carpet tack strips, razor blades or fish hooks on poles don't work well, are dangerous to humans including children, and are not considered humane.

No predator guard is 100% effective, but a decent one is always better than nothing!

Also see:

• The problems associated with mounting boxes on trees
• How to make a wobbling stovepipe guard
• How to make a conical baffle
• How to make a Hutchings PVC "coon" guard
• Predator and Problem ID and solutions

Note: Some folks just use an upside-down, 5 gallon plastic paint/joint compound bucket, with the metal bail/handle removed. Drill a hole in the middle of the bucket bottom. Keep it at the right height with a hose clamp underneath (mounted on the pole), or on two wooden blocks clamped to the pole with two long deck screws. (Thanks Dan Hanan for this description.)

• Galvanized stove or vent pipe WITHOUT A SEAM (expensive, can be purchased in long sections and cut down - try Aubuchon's or a place that sells wood burning stoves) OR with blind/pop rivets (e.g., type available at Lowe's) 8 inch diameter x 24 inch long (you don't have to cut it - it comes in 2 foot sections.) Note: A black matte finish will probably rust - galvanized is better.
• Circle of 1/2 inch hardware cloth that is 1" bigger than the stove pipe. Hardware cloth is flexible wire mesh available in hardware and garden stores.
• Two hanger iron straps (also called plumbers tape), 7 inches long
• Two No. 8 B32 x 3/4 inch machine screws and nuts

This baffle designed by Ron Kingston deters snakes, raccoons, opossums and cats.

Instructions: Put the baffle on BEFORE you put the nestbox on.

1. Use tin snips (offset are best) to cut a hardware cloth circle that is 1" bigger all around than the stovepipe. Be careful of cuts and scrapes - see alternative.
2. Cut a small hole or "X" in the middle of the circle (the diameter of your pipe - usually 1/2 to 1 inch.)
3. Put the circle over the top of the stovepipe. Then bend the edges down one inch all around so it it fits tightly INSIDE the stovepipe.
4. Cut three tabs in the top of the stovepipe. Bend these over the hardware cloth.
5. Bolt the two strips of hanger iron (or a hose clamp) securely on either side of the mounting pipe, and bend them to support the hardware cloth. Duct tape wrapped around the pole helps hold the hanger iron in place.
6. Doublecheck that there are no gaps that would allow snakes to squeeze through. You can take a slotted screwdriver and use it to pry the hardware cloth up against the stovepipe sides.
7. Slip the assembled baffle over the pole until it rests on the hanger iron bracket. The baffle needs to be at least four feet off the ground. The baffle should wobble a little to discourage climbing predators.

Also see drawings and instructions here or here .

Notes:

• If stovepipe begins to rust, snakes may be able to get purchase. Take them down, lightly sand and paint with exterior gloss or semi-gloss enamel to keep them slick and make them look better.
• Snakes (especially large rat snakes) may be able to climb a stovepipe baffle that has a seam. Try a metal "tent" baffle to seal the top of the baffle and extend it away from the pole far enough that the snake can't go around the baffle. (Thanks Jimbee).
• When mounting nestboxes on a T-post, cut two slits (in the shape of an X) in the hardware cloth and slip it down over the post. It will be snug, but the baffle will still wobble. (Thanks Evelyn)
• If the mounting pole is not dead vertical and the stovepipe rests against the pole, snakes may be able to crawl up over it.
• A commercial guard is available but it is only 8" tall, which will not deter most snakes. They work for squirrels though.
• If the box is mounted on a large wooden post or utility pole, you can make a version of this guard out of metal air conditioning duct, which comes in flat pieces. If the baffle is over 12" wide it doesn't need to wobble, as raccoons can't hang on.
• Raccoons have been known to defeat cone baffles.
• Snakes often take babies that are just about to fledge.
• Alternative to hardware cloth: use pre-made stove pipe caps instead of hardware cloth. Drill a hole in the center of each cap (slightly larger than width of the pole) and placed a flat metal disk above a large hose clamp to support the baffle but allow it to wobble. Put a few screws through the cap and the stove pipe to make sure they don't come apart. (Thanks Nina)

PVC PREDATOR GUARD - Material List:

• 4 inch thin wall PVC at least 2 feet long. (Note: 8 inch PVC works better for raccoons if the baffle is not wobbly.)
• 4 inch PVC cap
• a few screws
• a conduit hanger or a hose clamp.

Instructions: Put the baffle on the pole BEFORE you put the nestbox on.

1. In the top of the PVC cap, drill a hole in the middle that is about 1/8" larger than the mounting pole.
2. Use an oversized hose clamp (placed below where you want the PVC cap to rest on the pole - a few inches below the bottom of the nestbox) to make the baffle swing freely and wobble.
3. Glue (plumber's glue) or put a screw through the PVC cap so it doesn't come apart.

Notes:

• This baffle will prevent mice, raccoons, cats, etc. from climbing the pole. It CAN be climbed by snakes!
• It can be painted with Krylon paint to blend in, and may be available in a variety of colors.
• This set up may be more expensive than the stovepipe.
• Some users have had problems with paper wasps nesting underneath the PVC cap.

Mounting and baffle drawings courtesy of the North American Bluebird Society website. Thanks to Pam Spielmann for stovepipe baffle photos. Some information here is from The Bluebird Monitor's Guide