Keep Nestboxes From Becoming Lunch Boxes

Putting up birdhouses is a great way to provide habitat for native cavity nesting birds. Most songbirds such as bluebirds, swallows, wrens, titmice, and chickadees nest in cavities. In the wild they locate cavities in trees, but in a suburban environment such nest spaces can be few and far between. If you put up a birdhouse or nest platform it's important to be a good landlord to your feathered tenants. If you're aren't prepared to monitor, clean, and protect birdhouses then you might want to content yourself with just enjoying the occasional visitor to your yard. In our video Tricia gives you advice for choosing, placing, and maintaining birdhouses. So how do you keep those birdhouses from becoming bento boxes for hungry raccoons, snakes, cats and squirrels? The first defense is an appropriate location, followed by a predator guard. There are three main types of predator guards that are easy and inexpensive to build.

Building a Baffle

The most effective, but most difficult build of the three is called a baffle. Baffles are constructed using a length of 8" stove pipe or ducting over the pole your birdhouse is mounted on. A pipe less than 8" is not particularly effective. This type of guard keeps out raccoons, snakes, squirrels, and cats.

To construct a baffle you will need:

8" Diameter Galvanized Stovepipe or ducting 24–36" long 8"circle of hardware cloth or 8" duct cap 2 iron hanger strips or 3" long bolt with the head cut off 2 #8–32 x I" machine screws and nuts Tin snips Leather gloves Attach your iron hanger strips to the pole where you intend to mount your birdhouse on. The end of the baffle should be at least three feet above the ground, so secure the hanger strips 5-6' off the ground. The baffle needs to be at least 6" from the bottom of the birdhouse. Next assemble the baffle. If you are using a duct cap, drill a hole large enough to accommodate your pole in the top of a duct cap and secure it to the length of duct. If you are using hardware cloth use the tin snips to cut out an 9" circle. Snip a hole in the middle so it goes over the pole. Fit the hardware cloth into your duct or stove pipe. Some needle nosed pliers might be helpful bending the hardware cloth to fit. Cut four tabs, two inches long, and bend them over the hardware cloth so that the pipe hangs. At this point you can paint your baffle for aesthetic appeal. Slide the baffle over the pole so it rests on the hanger irons and you're finished!

Building a Cone (Zeleny) Guard

A cone also works for raccoons, snakes, squirrels and cats but is not quite as effective as the baffle. However, cone guards can be easer to build than baffles. Big snakes can get around cone guards and sometimes raccoons can figure them out.

To build a cone guard you will need:

3' x 8' sheet of 26 gauge sheet metal (one sheet makes three cone guards) 2 iron hangers 1 old tennis ball Galvanized nails 1/4" round head stove bolts or metal screws Tin snips Leather gloves Find a straight 21" stick. A stir stick for a 5 gallon paint bucket works really well. Drive two nails 18" apart in the stick. This is your home-made cone guard compass. Measure 18" from the top and side of your sheet metal, and insert one side of nailed stick in the center. Swing the other end around so it scores the metal. For the cone to fold properly, you will need a cut out triangle that is 9" at it's base. With your compass in place, mark a line down with a permanent marker. Take a ruler and measure 9" from the end of the line you just drew. Make another mark where 9" on the ruler intersects with the circumference of the guard. Slide your compass around until it is over the 9" mark and make a dashed line from the center of the disk. This line won't be cut, it's just for reference. Measure two inches from the second line and draw a line parallel to the second side of the triangle. This will be the overlapping section of your cone guard. Make a smaller wood and nail compass for one inch larger than the diameter of your pole. For example, if you have a 6" diameter pole, cut a 7" circle in the center. You can make 1 1/2" tabs in the inner circle that will be bent up and nailed to the post. Take the tin snips and cut out the circles. Cut out your triangle first and then around the circumference of your circles. Fold your cone guard into a cone so it overlaps to your dashed line. Secure it with the stove bolts or metal screws. If you made tabs simply screw the tabs to the pole. If you didn't use the iron hangers, cut the tennis ball in half and cut an x in the top. Slide the ball over the pole so it rests on the iron hangers and the cone guard will rest on top of that.

Building a Noel Guard

The last guard is a Noel guard. This type of guard goes on the front of the nestbox and prevents predators like raccoons or cats from reaching inside to get at the eggs and nestlings. It's not a barrier to snakes. If snakes are not a major predator in your area a Noel guard may be the way to go. Noel guards are best installed after eggs have been laid because some birds, particularly bluebirds, may not choose a box with a Noel guard. Chickadees and wrens have no problems with choosing a Noel guarded box. In fact, wrens seem to enjoy the guard.

To build a Noel guard you will need:

½" wire mesh hardware cloth 7" × 18" if you have determined raccoons you might want to use a 9"x18" piece 4 1¼" screws or staples Tin snips Leather gloves (optional) Adapter plate Cut out your hardware cloth as shown in the above diagram. Bend out one square of the hardware cloth on the longer sides and staple it to the front of the birdhouse or to an adapter plate that can be attached to the front of the birdhouse after the first eggs have been laid.