One question I've been asked a number of times is about Predator Guards. Are they really necessary? What would happen if I didn't use them. Well, the only thing I can say is, if you want to protect your martins, then I strongly suggest they be used. Snakes and raccoons won't hesitate for a moment to make a feast of your purple martin colony.
Many times predator guards can be rather expensive, especially if you have more than one pole to guard. Also there really isn't a big selection on the market today with only a few manufacturers making them that I know of. So, since I'm big into making my own stuff and this is a very simple project that has a lot of benefits for the martins, I thought I'd put together a page showing just how easy it is to make an effective predator guard that will work and won't cost you an arm and a leg.
The first thing you'll need are a few materials and tools. About the only thing that is special here is some way of cutting the material we'll be using for the guard. In our case, it's galvanized steel flashing that can be purchased at just about any hardware store including Lowe's and Home Depot.
Take a look at the picture below. It shows all the tools needed to make the guard.
You'll also need a jigsaw to cut out the disk and the holes in it,
a pair of sheet metal shears to cut the flashing,
a 1/2" drill to drill the rope clearance hole,
a regular hammer,
a dead blow hammer,
a framing square,
a compass,
and other marking tools for drawing on sheet metal.
You'll also need a very dull utility knife for scoring the tin to make bending easier.
I designed this page for the average garage handyman with a few hand tools, but if you have other power tools that'll make the job easier, then by all means, use them.
The general materials list is as follows:
1 piece of 24" wide x 34" long galvanized steel flashing. (Aluminum flashing is a little too weak for this use).
1 piece of 10" x 12" x 3/4" thick exterior plywood.
1 small piece of 1/4" thick stock. Just about anything will do.
You'll also need a small 5" piece of old garden hose and a hose clamp large enough to go thru the hose and around the pipe.
You'll need a hammer and nails or some one inch long bugle head screws and a screw driver. A driver in a drill really makes things a whole lot easier.
You'll need 4 - 1 1/4" long bugle head screws to mount the squeeze brackets.
You'll also need a half dozen small brads long enough to hold 1/4" stock.
Oh yeah, I also suggest a pair of safety glasses and a good pair of gloves if you're not used to working with metal sheeting. Sharp edges cut pretty easy if you're not careful.
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The top of the guard is simply a round disk made out of exterior plywood. The one I made is exactly 10" in diameter. Measure in 5" from two edges of the plywood and draw a center point. Using a compass set to 5", draw the outside of the disk.
Then, draw a line right thru the center of the circle.
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Now using the jigsaw, carefully cut out the round disk, leaving the line. Go slow and be accurate. Remember, you're working around the circumference of a circle, so any little inaccuracies will add up quickly.
Once the disk is cut out, mark and cut a hole that is 1/8" bigger than the pole you are putting it on.
Next, drill a 1/2" hole off to one side, leaving 1/2" of material between the large center and 1/2" hole.
Finally, cut the disk along the centerline you drew on the disk, thus making two halves.
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Now, while we're doing the wood work, make two small 'squeeze' blocks from the scrap left over from cutting the disk. They are 3/4" wide, 3/4" thick and 2" long. Drill two small screw clearance holes in them as shown.
Next make two alignment plates. They are 1/4" thick, 1" wide and 2" long. On one of them, make a small 15 degree angle cut on one side as shown. I used a scrap piece of 1/4" thick plywood for these.
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I'm one of those people that never throws anything away. Some time ago I got a package in the mail and it had some nylon banding on it to secure it. Yep, I saved it thinking I'd probably find a use for it somewhere down the road.
Well, I found a use...a hinge. I cut a 6" piece of it and tacked it to the back of my disk as shown. It works great and didn't cost me a penny. You can find this stuff anywhere shipping is done and if you ask for a 6" piece, they'll probably just give you a piece. If you have more than one guard to build, then sweet talk them and get some extra...
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Now turn the disk upside down and add the two little alignment plates as shown. Put the outside (square) one on first locating it approximately as shown. Tack it to the left side of the disk.
Now add the one with the angle on it, tacking it to the right side of the disk, angle facing the first plate as shown. Leave about 1/8" between the two plates. The reason for the angle, when you open the disk, the angle prevents the inner plate from hitting the outer plate.
The reason for these plates, they hold the front of the disk together when it's on the pole. Neither side is able to slip up or down.
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Now that the disk is done, squeeze it together. Then take a tape measure and measure the exact outside circumference of the disk. (Write it down somewhere). It is important to be accurate. Now, add 2 1/2" to that dimension. That is the dimension that you will cut the length of your flashing to.
Measure the flashing very carefully. I used my framing square against the side of the flashing to make sure that I drew my lines very accurately. Steel flashing will lay fairly flat on the work table, so this part is easy.
Now, this is where my dull utility knife comes into play again. (The same one I used to make my starling trap floor). Using the dull utility knife, drag it across the sheet, scoring into the material. Because this is steel, you may have to draw it a couple of times, you want a good score.
Next, fold it back onto itself, bending it exactly at the score line. If your score was deep enough, it'll bend exactly at the line. Squeeze it together and then unfold it again to flat, then bend it again and then back to flat again. Do this until the metal simply breaks along the line.
PLEASE BE CAREFUL! This stuff is sharp!
Once the flashing is cut, carefully measure and mark two lines, one half inch apart from the end of the sheet.
Now, flip the sheet like you were turning the page of a book and repeat with the two half inch lines. The lines must be on opposite sides of the sheet from each other.
Now, using the marker, designate the TOP of the sheet. As you're looking at it, the bottom is near your belly and the top is the edge furthest away from you. Simply write top on it up near the edge in the right hand corner...yes, it is important.
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Now, turn the sheet 90 degrees to the right (clockwise), and using the sheet metal sheers, cut out a piece that follows the inside line and is 6" long.
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Now you have to bend the material and to do this, you have to score the material. This gives you nice clean bends.
Turn the sheet 90 degrees to the left (counterclockwise). Laying your framing square exactly on the outside line, carefully score the material. Remember, this is steel, so you don't have to be shy, you might have to score it a couple of times to get a good bend line. Do this for both of the lines on the first end.
Now the first end of the sheet can be bent.
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NOTE:
Bending always bends towards the lines, therefore, flip the sheet over (black lines down towards the table) and lay the first scored line right on the edge of the table. If you don't have a table, you'll need something with a sharp edge to get a good bend.
Using a dead blow hammer, gently start bending the material down against the side of the table. Take your time and don't try to bend it all at once. Start by tapping about every 3", then come back and catch the parts in between and then again back and forth until the the first flange is flat against the side of the table.
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Now flip the sheet over and finish flattening the first bend right back onto itself. Go easy! Don't try to do it all at once. Maybe start in the middle and work outwards, bending the sheet a little at a time, then back and forth until the entire flange is bent flat against the table.
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The sheet should look like the photo below when you're done.
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At this stage, at the bottom of the 6" you cut out, take your tin snips and cut the bent flange at a 45 degree angle as shown. This will reduce the sharp corner when in use at a later stage.
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Again,
flip the sheet over and using the dead blow, bend the second flange down and
flat against the table edge.
Remember, black line down...
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This time, we're not going to bend it flat on itself. Instead, lay your framing square up against the bent flange and then begin bending it over the square. You do not want to close this bend flat on itself. You'll see why later on...
Flatten it against the square so when you pull the square out, it'll have a channel under the flange.
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Now, flip the sheet like the page of a book again and repeat this same procedure for the other end of the sheet marking the two 1/2" lines like before and scoring them.
However, there is one difference here. Take your disk circumference measurement and measure from the edge of the first cut across the width of the sheet and draw a mark. Be accurate! It should measure close to 31 1/2" if you have a 10" disk. Now, subtract 1/8". This should give you a dimension of 31 3/8". That will be the line where you cut the 6" at, NOT at the bend line. Before you cut, make sure that both cuts are on the same edge of the flashing. The reason for this is so that the metal won't overlap when you close the guard. Now, you can finish bending the second end using the procedure from above. The flanges will end up on OPPOSITE sides of the flashing.
Once the second end is bent, roll up the sheet like you would roll up a newspaper. When it unwinds, it should be in a somewhat round circle. The word TOP should be on the inside of the roll.
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Now we're going to add the bent sheet to the disk.
Turn the disk upside down on the table with the front facing you.
Stand the sheet so that the TOP of the sheet is setting flat on the table. The 6" cuts should be down and the first flange you bent should be facing in. Place it around the disk and locate the cut edge even with the center cut of the disk.
I used a pneumatic staple gun for this part. If you don't have one, then you can use either nails or pre-drill holes and use the 1" bugle head screws. You want one about every 3 inches. Start with one close to the edge of the sheet as shown. About a half inch should be fine.
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After the first couple of screws/nails are in place, you might find it easier to turn it on its side like I have shown to continue around the disk. Go all the way around the disk finishing with a nail or screw close to the other end of the sheet. Keep the edge of the sheet and disk flush so the guard ends up square on the disk.
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Now you can add your two little squeeze blocks.
Stand the guard on end and leaving about 1/8" in between the blocks, screw them in place as I have them shown below with 1 1/4" bugle head screws, one on either side of the disk. These will help immensely when closing the guard when it's on the pole
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Now, before you go any further, REMOVE ANY BURRS OR SHARP EDGES. Do this with a piece of sandpaper wrapped over a small piece of wood. (A small file will work also). DO NOT TRY IT WITHOUT THE WOOD. The metal will cut thru the sheet of sandpaper and then it'll cut you. Take your time and get all of them. Make it nice and dull.
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Now, by squeezing the two squeeze blocks together you can close the disk. About mid way down the guard use your fingers to work the outside flange over the inside flange. (Now you know why you didn't want to make the second bends flat).
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If you bent your material correctly, it'll fit right in. Make sure the grooves fit all the way up. If your guard doesn't fit tight, open it back up and grabbing both bottom edges, force it open, effectively taking some of the roll out of the metal. This will put a little more force into the flanges holding it together better.
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Now when you let everything go, it should form a nice round 10" predator guard that will fit on your pole. There might be a small crack in the wooden disk, but that's OK, nothing can get thru it. The flanges fitting good are the important thing.
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Now we can put the guard on the pole.
Take the 5" piece of old garden hose, (I told you I don't throw anything away), run the clamp thru it and then attach it to the pole as shown. Mine is about 2" above the top of my rope tie.
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Next, take your guard apart. Start at the bottom of the guard and separate the flanges, working your way up until the whole thing is undone.
Place it around the pole over the hose clamp and then reconnect it placing the rope in the 1/2" diameter hole you drilled.
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And when you're done, you should have a pole guard just like the one shown below.
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Since my poles are black, I decided to paint my guard black also. It actually stands out a little less than the shiny steel one would, plus the paint helps protect the wood and the bare edges of the steel.
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And, for about an hour of time spent in the garage or shop and a few inexpensive materials, you've added a large measure of protection for your birds and a great deal of 'piece of mind' for you.
A couple of points:
NEVER let the guard set on the ground. You want the top of it to be at least waist high with the bottom well off the ground.
YES, it is supposed to flop. If any wild creature tries to climb it, it will flop all over the place and any wild creature will not climb onto anything that it can't get a good grip on. With it up in the air, anything that does try to climb the pole will have to start on the pole first and then work on negotiating the guard while trying to hang on the pole at the same time. Coons can't jump that high and snakes will have to wrap too much of their bodies around the pole first to have anything left over for the guard.
Since all the rope is piled up under the guard a predator can't use that as leverage to get around the guard.
Do they work? I don't know! All I can say is I've never had a snake climb my poles to get at my martins.