Sunday, July 26, 2020

Nest boxes for Tree Swallows

Nesting box installed on an endpost in my vineyard. The opening is facing north-east to avoid inclement weather.
Yesterday and today's project is to build and install nest boxes for Tree Swallows.

I had been feeling pretty good about how few Japanese Beetles were in my grape vines. I attributed it partially to the wet spring rotting the pupating beetles and partially to a robin nest in a pear tree near the west end of the orchard/vineyard. Those baby robins eat a lot and the grape vines were the closest source of an easy meal.

Rather than leave birds nesting in my orchard/vineyard to chance I decided to put up some nest boxes for one of my favorite birds: Tree Swallows.

As you can see from the range map, Tree Swallows breed in the northern half of North America and Michigan is pretty close to the middle of the range.

Not only are the Tree Swallows likely to eat a bunch of Japanese Beetles but they will also eat biting flies on cattle.

The basic plan from HERE 
Having been an engineer in a previous life, there is no design that I cannot make better. Or, if not better, more complicated.

Instead of a hole, I opted to go for a slot. Advantages discussed HERE. The primary advantage is that a properly sized slot is more effective at excluding English Sparrows than round holes. English Sparrows are probably the #1 cause of small, cavity-nesting bird reproduction failures.

It is also easier to construct.
A $3 Gutter-Outlet used as a raccoon guard.

The second modification was to use a common "gutter outlet" typically used to connect down-spouts to gutters as a raccoon guard. I used the 3" version but the 4" version would probably be better.

Here is a picture of a more typical raccoon guard. The mesh extends far enough out that a raccoon cannot sit on the roof and reach in and grab nestlings or parents.
A view looking up, into the gutter-outlet showing that none of the slot is obstructed. I think it is important to have the top of the gutter-outlet as close to the top of the slot as practical to deny the raccoon's arm a chance to pivot downward at the elbow.
I used a piece of dimension lumber to shim the gap. 1" dimension lumber is 3/4" after drying and planing. I "eyeballed" the additional 1/8" but you can add a paint stir-stick to the thickness of the dimension lumber if that makes you more comfortable setting the gap.

I screwed the top piece on first (a 1"-by-2" piece). Then I used the shim to determine how low to put the bottom piece of the front.

The other minor modification was to not rip standard 1-by-6s to 5 inches. It seemed like non-value added work.

I can get a little bit more than 3 boxes out of an 8' 1-by-6 and an 8' 1-by-8. Including the cost of the Gutter Outlet, I have about $8.50 into each box.

This box was the beta version. Now I have eight more to crank out. I don't expect any swallows to nest in them this year but they will be waiting for them when they come back next spring.

In the "For what it is Worth" category, Tree Swallows are not highly territorial. They will accept nest-boxes that are 100 feet away from another pair of nesting Tree Swallows.

House wrens are the other small species of cavity nesters that might use these boxes. I like House Wrens and will be fine if they take advantage of some of the boxes.

We don't have many rat snakes around, so I don't expect them to be a major predator of the Tree Swallows.


  1. Sparrows are a PITA for MANY reasons... Grrr...

  2. I have 20 nesting boxes up for the tree swallows and bluebirds. They use the same ones. I put them up on my fence posts one on each adjacent post, skip a post and then another pair. That way when the tree swallows come back a week before the bluebirds they will usually skip every other house so the bluebirds get a home also. But not always, sometimes the swallows will nest in adjacent houses. The swallows train their young in flying and bug catching then leave for the year. I only have one family left here now and I expect them to leave soon. I love to have them here. ---ken

  3. Wouldn't a metal pole be a lot less trouble than your approach? It solves coon problems. Snakes, I don't know. We only have garter snakes, or less, here.

    I put up some nests this year in June but it was too late. There is a narrow window for nest choice. It takes them a long time to build a nest, like 2 weeks. Feathers are highly desired feature and they will travel 20 miles to find them. I remember as a kid mom giving them feathers out of an pillow and they went nuts. Clean untreated feathers, of course.

    I assume your box has a way to clean it. They get nasty with parasites and the mites are to be avoided by people, too. A friend suggested diatomeseas earth added to a cleaned box. Wood ash might work, too. Some birds love it as dusting material but I don't know if it is ok.

    There is loads of info on line about proper swallow boxes. I looked into it in June and saw a lot of our old ones were wrong. Most were meant to sell. The wood was thin, too small, the paint was too dark, there was a peg under the hold, and worst of all, no easy way to clean them. Some were ridiculous like one with two nest holes facing each other 4 inches apart.

    A hole facing south is said to be preferred although everyone wants them where they can see them. The one facing the house was all wrong but still produced chicks.

    We neglected ours. They should have been inside for the winter but that is a logistical hassle since they need to be back up in April or May and we may not be there. We are deep in the country so sparrows and starlings are less of a problem.

    On another note, I was at a working farm on the 16th and the owners and l saw 10 barn swallows apparently newly on the wing. They were the first l had seen in years. The owners were surprised, too. Barn swallows are way down, like 90%.


    1. I noticed something odd this year with the house nest. I saw the front was covered in droppings. I thought it was the adults. I scrapped it off and there was more the next day. I watched the little guys with binoculars from inside the house and one guy swung his butt out the hole and let fly. I thought, do they do that? It was a smooth practiced move, it appeared, but I only saw it once. I noticed a pile of droppings under the hole so something was happening. Further watching showed the adults carrying droppings away in their mouth and, wow, you thought your parenting was tough!

    2. I will have to keep an eye on that. I may have to trim the bottom out of the raccoon guard so it doesn't fill up with bird poop.

    3. On my houses I put the bottom piece in with two screws and when I get around to it before they come back take my cordless drill out and take off the bottom and dump the old nest. I have boxes facing all directions and have never noticed any difference in occupancy. But those are Yooper Tree Swallows so they're tough dontcha know. What I have noticed being down the past two years is the Blue Birds. Lucas is correct, the adults clean up the nest.--ken

    4. Regarding cleaning: I settled on three, 2" deck screws to hold the front on. If you look at the picture, you will see the front is in two pieces. A 1X2 on top and a 1X8 by 7.5" on the bottom. It is the bottom piece I plan to remove.

      Some of the boxes are going on metal T posts in the pasture. I will have to run a hot wire around the bottom to deter the cows from rubbing on them. If I also loop it so the raccoons, etc run across it while they still have a foot on the metal pole...well, I think they will get a solid poke.

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