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, such as the bluebird wing below, is terribly
disheartening.  You must take steps to reduce chances of this happening.  Careful
choice of project site and proper location of boxes greatly reduces 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, opossums, weasels, and cats 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.  
  • 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 as difficult and unpleasant as possible!  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).









  • Can and Grease Guard:  A simple and cheap guard may be made using large
    juice or restaurant supply cans.  A can's ends are removed and its sides are cut
    in strips that are bent out.  One cut goes all the way to the end so the can will
    fit around a pole.  









  • The guard is supported by three pieces of house construction "hanger strap"
    secured to the pole by a hose clamp (below left).  











  • Two or three cans are then fitted on the pole.  Be careful handling the cans;
    their edges may be sharp!  
  • Adding a band of engine grease 6-8 inches wide directly below the predator
    guard makes the barrier even harder for predators to pass (see below).  This
    grease also discourages ants from reaching nests.  























  • Note: If you decide to use can guards and grease, don't put them on right away.
  • 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 egg-laying, swallows competing for
    boxes could be injured by the can edges or get their feathers fouled by
    grease.  
  • So, if you use can guards and grease, wait until your females have begun
    incubating their eggs.  








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Learn About Birds at Tree Swallow Nest Box Projects
Predator Protection