Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters
 
bluebirds

eggs

KERFS

QUICK TIPS: Put saw "kerfs" or rough up in the interior of a nestbox under the entrance hole to help young exit the box

A "kerf" is just a groove cut in wood/other material below the entrance hole of a nestbox to help nestlings exit when fledging. Kerfs may prevent fledglings from dying in the box.

It is easiest to put kerfs on before mounting the door panel on the box (especially saw kerfs.) You can also take the door off and then re-mount it.

How to make kerfs (some options):

  • When building or assembling a box, put the rough side of the wood towards the inside.
  • Open the door and lay it flat on a workbench so as not to destroy the hinge nail alignments. Then on the inside of the door, below the entrance hole/slot:
    • take a large cold chisel and randomly"ding" or rough up the surface in that area making small pits in the door surface.
    • The same thing can be done with a Wonder Bar, a large Phillips head screwdriver, the handle end of a file or an ice pick/awl, or a dremel tool.
    • You can also use a router, table saw or radial arm saw (lower the blade into the wood but don't go all the way through!) You can make grooves 1/8" deep at 1/4, 1/2 or 3/4 inch intervals, and put them all the way from just under the entrance to just above the floor.
    • When working with cypress, cypress, anything less than about 5/16" between the closest edges of two kerfs results in some wood chipping.
  • Kerf on interior of Peterson door
    Thin horizontal beads of "Liquid Nail" or GE silicone caulk can be used in PVC boxes, laid out like rungs of a ladder or in squiggles. Spread it with a plastic trowel made to place floor adhesive for sheet goods to create a series of evenly spaced ridges.
  • Staple plastic gutter guard or fine nylon mesh under the hole. Note that rarely feet can get tangled in the cloth (especially if it is loose), resulting in death.
  • Take a small piece of hardware cloth and cut to size (about 3" wide). Position on the inside of the box just below the hole. Drill a hole a couple inches below the hole and use big aluminum pop-rivets and washers that are used for fastening gutter downspouts to lock it in place. If you need to remove the wire in the future, its easy to drill out the soft aluminum rivet. Make sure the edges of the hardware cloth that are cut with a snips are curled into the side of the box a little, as the snipped wires are razor sharp.

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I learned that it STILL hurts ones heart to lose a nest full of babies, even after all these years, after losing babies before, and knowing I'll lose babies again, it STILL hurts..... Even thought I KNOW that it's the "circle of life" and that is how things are suppose to go sometimes, it STILL hurts.
- Joy in Michigan, Bluebird_L, 2006

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