Will predators attack your swallows?
There's always danger of predation, so protecting your nesting birds is a crucial
responsibility for you as a nest box project manager. Finding boxes emptied of eggs or
young, or discovering discarded wings, legs and clumps of feathers below a box is
terribly disheartening. Please take steps to reduce chances of predation.
Careful choice of project site and proper location of boxes will limit risk of predators
finding your boxes, but you should also try to prevent predators from reaching any
boxes they do happen to discover.
What animals predate nesting Tree Swallows?
- Raccoons, cats, and opossums will kill and eat any adults and young they can
pull out of boxes.
- Raccoons are especially dangerous because if they find one box and can
predate it, they look for other boxes and may predate every box in a project.
- Squirrels are also important predators of cavity-nesting bird eggs and young,
and if box entrances are too small squirrels can chew their way in. And
chipmunks, though cute, predate more bird nests than most people realize.
Photo below by Barry Scully.
- Weasels are so slender they can enter most boxes they can reach. The photo
below of a Short-tailed Weasel exiting a predated box is by Barbara Russell.
- Most snakes can't climb poles, but a few species can, and will enter boxes to eat
eggs, young or adults trapped inside.
How can you stop predators from reaching boxes?
- Make it difficult and unpleasant! The best method is to attach a predator guard
to the pole below the box.
- You should use a guard on every box because raccoons and climbing snakes
can get up even thin metal poles surprisingly easily, as the photo below taken
during experiments conducted by bluebird expert Keith Kridler demonstrates.
- Conical and Stovepipe Guards (see below) are somewhat effective, but they
can be expensive to make and very expensive to buy.
- Hardware Screen Guards that project out around the entrance hole are less
expensive, but they make it difficult and time-consuming for adult swallows to
access nests when feeding nestlings. (Note the overlarge hole and small
dimensions of the box below, obviously not a good design for Tree Swallows).
Our System - Can and Grease Predator Guards:
We use simple, cheap guards made using large juice or restaurant supply cans.
- Can ends are removed and the sides cut in strips that are bent out.
- Note: One cut goes all the way through so the can will fit around a pole.
- Warning - Can edges are sharp!
- The cans are supported by three pieces of house construction "hanger strap"
fastened to poles by hose clamps.
- Rounding the portions of the hangers that touch the poles makes them fit better
and allows them to be tightened more securely.
- Three or more can guards are then stacked loosely on top of the hangers.
Caution: Don't over-do the grease! Use only a short band, if you use any at all.
- Adding a band of engine grease 4-6 inches wide directly below the predator
guard makes the barrier even harder for predators to pass (see below).
- Plus, this grease also discourages ants from reaching nests.
- Some ant species will build nests within bird nesting material inside boxes, where
they may disturb or injure young birds and cause adult birds to desert.
- Note: Additional grease may need to be applied during a season.
Caution: Wait until females begin incubating before adding can guards and
- Most predation by mammals occurs at night. However, male Tree Swallows
almost never roost overnight in boxes, and females usually don't until they've
begun to incubate their eggs.
- If can guards or grease are added before or during egg-laying, swallows
competing for boxes could be injured by the cans' sharp edges or get their
feathers fouled by grease.
Learn About Birds at Tree Swallow Nest Box Projects
|Creating Projects, Tree Swallow Basics, Finding a Good Site, Building Boxes,
Box Location, Pole Options, Mounting Boxes, Nest Box Grids, Predator Protection,
Bluebird Competition, Martin Competition, House Wren Damage, House Sparrow Damage