Bird Observer - The New England Birding Journal

Bird Observer

The Birding Journal for New England

October 2015

Vol. 43, No. 5

Barred Owl Adventures in Hampstead

Alfred Maley


Barred Owlets (All photographs by the author.)

Field of Dreams

Twenty-five years ago I put up a Barred Owl nest box on our one-acre lot in Hampstead, New Hampshire, because I had heard owls in the forest behind the house and I am an optimist. Alas, Hampstead proved to be a desirable location for people. The forest was subdivided, followed by high-grade lumber harvest, lot clearing, road building, and 22 new houses on 2–10 acre lots. Towhees began to nest.

Plan B

Undeterred, I looked to the conservation lands—which I was steadily accumulating when I was chairman of the conservation commission—especially along nearby Darby Brook. The original nest box design was structurally weak and very heavy, but I improved it and added a ceiling mirror so the contents would be visible from the ground. Soon I had three boxes erected and occupied, closer together than I thought was possible, and I placed additional boxes, also close together, on the Main Street conservation lands. By the spring of 2013, there were five occupied nest boxes, each kicking out two owlets year after year. No box, once occupied, ever became unoccupied. That was probably due to proper design and construction and a raccoon guard.

Back home my original owl nest box had long been a favorite of Wood Ducks, so I had concentrated on duck nest boxes instead. By the spring of 2014, there were 11 nests in the yard (eight Wood Duck, three Hooded Merganser). For good measure I had also put up another owl nest box of the new design with a mirror so that I could monitor the contents from the ground, even if it was only ducks.

Return of the Forest and the Owls

Fast forward to 2014 and the forest behind me had grown. The canopy had closed over again, the towhees were gone, and the trees were getting big again. The road and the houses were still there, but they began to blend in with the trees more and more.

In the fall, I placed my usual frozen Thanksgiving turkey out near the nest boxes and noticed one or more Barred Owls visiting the turkey early in the morning, 4:00– 5:00 am. I took that as a good sign as we headed off for the winter in Spain.

Not So Many Ducks

When we returned in late April 2015, there were fewer duck nests in the yard—six—which I ascribed to the gray squirrels which had taken advantage of the absence of any skilled marksmen. But NO, there were owls in the ’hood! The mirror revealed an amorphous gray blob in the bottom of the new owl box, which over the course of May resolved itself into three gray blobs. The adults were around, but reticent to show themselves.

Crafty Ducks

When the ducklings started to fledge in May, the females were keenly aware of the owls. Normally only the female owl would be present, close to and guarding her nest box. The ducks went to great lengths to circumnavigate the nest box and remain out of sight of the owl. Just one duck nest, which was 15 yards from the owl nest box and facing right at the female owl, suffered losses, but only two ducklings.

Bad Weather Strikes

May 2015 was dry, good for hunting owls that listen for mice, voles, and shrews scurrying though the leaves on the forest floor. But early June turned rainy and stress soon became evident. Only the adult male hunts, and he had to feed four mouths plus himself. After three days of rain, it became very difficult.

The Sora-like Call of the Female Barred Owl

About this time we began to hear the female owl give a nearly constant contact call, sounding like a listless Sora with the same upward inflection. She would give the call every 20 seconds or so for hours on end during daylight. I interpreted the call as “We’re here, bring food soon!” It was then that I began to notice that the male would announce his arrival with a food item and a downward whoaah. The female would go to him, receive the food, and take it to the young who were still in the box.

The Irresistible Urge to Intervene

It was at this time, with the female complaining incessantly, the male having trouble hunting, and the third owlet about to become lunch for its siblings that I started a rodent trapline in the yard. I put the catch on a platform in the woods below the nest box and the female quickly figured it out. On the best day my handouts included six chipmunks, two mice, and a shrew. The complaining nearly stopped.

The Young Fledge, But Don’t Go Far

At the nest boxes on the conservation lands, once the young fledged they were impossible to find as they secreted themselves high in the canopy. So I thought that perhaps they moved away in a matter of days. But at the box in the yard the young stayed around for over two weeks after fledging, perhaps because it took a while for the third owlet to get fully-grown and flying. As it was, he or she fledged nearly a week after the others. By the end of June, they were all ready to go.

The Sora Call Revisited

Once the young had fledged, the female, after receiving a food item, would turn around and issue the same Sora-like call but with some subtle difference to the ending that provoked the young to hiss, much like young Barn Owls do while still in their nest. I interpreted this call as “I’ve got food. Who wants it?” How the female interprets the responses of the young is unclear to me, but it may guide her as to which one to feed.

The Sora Call Yet Again

In late July, after the young had been wandering around the neighborhood for a month, they returned to the yard one night and I heard them giving a new call. Instead of just a hiss, they were giving a scratchy version of the Sora-like call with a hiss on the end, as if they were practicing for later in life. They wanted food and they wanted it now.

The Danger Call Around the Nest

The owls in the yard were habituated to us and never seemed to give an alarm call of any sort, at least when we were around the yard or at the nest tree. However, when I’d visit the owls in the conservation lands, they would frequently give a series of two to four loud rising hoop calls and fly about if there were young nearby that were fledged or nearly fledged.

What Goes Into Who Cooks For You

One afternoon in June, the male brought in a food item while the female was perched in the yard, clearly visible to us on the deck. The male, invisible in the foliage, gave the who cooks for you call. In response the female spread and lowered her wings and while pumping her tail down expelled each of the four syllables of the call. It’s an effort like one of the prairie grouse go through and tells me why they don’t do it for long. It must be exhausting. After one call the female took the prey item up to one of the fledglings in a nearby tree. I now suspect that when I hear this call on a late afternoon in June or July, it is related to a food drop, rather than territorial conversation.


Slide bar and chain method of attachment for Barred Owl box

Suburbia As Barred Owl Habitat

Is it good for Barred Owls to nest in suburbia? No, if there is a high-speed highway close by. No, if the neighbors use leaf blowers all spring long—a deaf owl is a dead owl. No, if your neighbors use rodenticides in their gardens “to control those pesky voles.” Otherwise, sure. The food supply is probably better in the winter because of the rodents at bird feeders, worse in spring and summer when the owls have to hunt all day long and human activity is at its peak. There has to be some good area close by to hunt in, with few human-inspired dangers.

How Many Owls Are Feasible?

This year, 2015, I had seven occupied Barred Owl nest boxes in Hampstead, and I may have another one or two next year. The number of Barred Owls seems to have increased locally, at least I hear them almost every night. Boxes that were initially unoccupied for several years all have become occupied. It seems clear to me that a shortage of suitable natural nest sites in second growth forest is more of a limiting factor than food supply, judging by the number of chipmunks I see.

Design Changes

Since the original article on nest box design (Maley 2010) I have made small changes. The entrance hole is one inch wider so you can get photos of two nestlings in it; the front, back, roof, and floor are all one inch wider so the box is square inside and larger; and the back has slide bars (see photo) so the box can ride up the tree as it grows circumferentially. The slide bars move the roof edge of the box out of contact with the tree and greatly reduce friction with the tree, while tending to stabilize the box against the curvature of the tree.

The box support, made of pressure-treated decking, is strong, easy to put up, and durable. It is especially easy to attach the box to the support, like putting a car wheel on the bolts of a hub. The boards are separated from each other by washers so they won’t rot, and the board ends are cut so as to shed water—they will last for a very long time. All of my original boxes used this system as seen in the photos in the previous nest box article. However, since trees grow outward (circumferentially), you have to be able to climb the tree every ten years or so and back out the lag bolts to accommodate the tree’s increase in diameter. Though perhaps not clear from the article photo, there are four long lag screws that hold the board off the tree. There are also four galvanized bolts that go through the board in the opposite direction and into the box, which is secured with washers and nuts from inside via the entrance hole. Make sure to put a nut between the board and the box so the bolts don’t move when attaching the box.

The new chain method (see photo) simply loops a chain attached to the box around the tree trunk and over a branch or a long lag bolt on the opposite side. The box hangs against the trunk by gravity and, as the tree widens in diameter, the box rises. This scheme might last for 15-20 years, and is especially useful where access is inconvenient.

The chain is partially encased in one inch black polypropylene water pipe, of the kind commonly used for wells. As it is somewhat rigid, I cut kerfs in the pipe so that it bends easily around the tree trunk. A 7/8-inch birch dowel inside the pipe keeps it straight while the kerfs are made using a table saw.

The two vertical pieces of pipe bolted to the back of the box serve not only to facilitate the box riding up the tree but also to conform the back of the box to the curvature of the trunk. Separate the pieces such that they just contact the trunk of a tree similar in diameter to the tree that will hold the box.

Placement Advice

The owls need to be able to approach the nest box head-on. There should be a clear flight path in front of the box, but not so clear that the young can’t find a branch to fly to when they fledge. I place all my boxes in hardwood trees near hemlocks or thick white pines. Hardwoods have few low branches and admit sunlight into the nest box so that the mirror works during the spring months when the trees are leafless.

To place the box at a reasonable height without great effort, try to find an elevation within the forest such as a small hillock with a suitable tree. Alternatively, put the box in a stream valley, facing the stream but up one valley side. My boxes are 15–25 feet above the ground, but there is no magic number. If you place a box in suburbia, try to get it as far away from leaf blowers and fireworks as possible.

Drop me a line at AlfredMaley@gmail.com with questions or comments on your successes.

References


Alfred Maley is a retired software engineer whose interest in nest boxes began at age 10, when he cobbled together a successful bluebird house with wood from an orange crate. Later came Barn Owl nest boxes and Long-eared Owl nest baskets. When they are not watching raptor migration in Spain or traveling with Danger Tours to Latin America, he and his wife Linda reside in Hampstead, New Hampshire.

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