Why do Tree Swallows use nest boxes?
Cavity-nesting birds like Tree Swallows, that can't make their own cavities, usually
face a shortage of nest sites.  Competition for cavities can be intense, even a matter
of life and death, since failing to reproduce is a critical failure for short-lived
songbirds.  Tree Swallows must compete for nest sites with other Tree Swallows and
also with other cavity-nesters like bluebirds, wrens, starlings and house sparrows.  
Since natural cavities are scarce Tree Swallows quickly accept nest boxes, and unlike
many other cavity nesting species they aren't picky!  They'll use just about any box
they can get into.  Their nests have been found in large houses for Purple Martins,
Wood Ducks and Screech Owls, and in such unlikely spots as drain pipes, mailboxes
and newspaper tubes (see the photo below by Laura Niang).  Sadly, they'll also try to
nest in unsuitable tiny or flimsy boxes where few if any young survive.















Be sure to build boxes designed specifically for Tree Swallows.
You'll want boxes like the one below, boxes built carefully of good materials, where
your swallows will be safe from predators and protected from rain and heat, ones
roomy enough so parent swallows can raise strong, healthy young.

We recommend both of the following two box designs.

Click here for the GOLONDRINAS BOX.  This will connect you to the box plan page of
the Golondrinas de las Americas (Swallows of the Americas) web site run by Cornell
University, where you'll find a design printable in either inches or centimeters.  The
Golondrinas project promotes and coordinates research into the biology, ecology,
and behavior of Tree Swallows and the eight other species in genus Tachycineta.  
Their design is the standard used for the thousands of boxes operated by Golondrinas
scientists at their 50 or so research sites throughout North and South America (see
map).

Click here for the LONG POINT BOX: INCHES or CENTIMETERS.  This is the box
pictured below and elsewhere on this web site.  We saw this design at the Long
Point Bird Observatory in Ontario, Canada, liked it, and modified it a bit.  It differs
somewhat from the Golondrinas Box and is more difficult to make, but we've used it
at Salmon Creek since 2003 and are very satisfied.  The above links take you to
printable files containing introductions to the Long Point Box and its features,
construction suggestions, and a detailed plan for cutting and assembling these boxes.



















No matter what design you use all Tree Swallow boxes should have:
  • Sturdy wood construction using 1" rough-cut boards or exterior-grade plywood
    at least 1/2" thick.
  • 1-3/8" to 1-1/2" entrance holes to keep larger birds out.
  • Entrance holes centered about 7" above floors.
  • Floors never smaller than 5" x 5".
  • Roofs that slope down and overlap sides and fronts, reducing exposure to rain
    and making it harder for predators to reach inside.
  • Sides that swing open for easy checking of box contents and cleaning.
  • Floors recessed to minimize interior wetness.
  • Unpainted interiors.
  • Roughened, kerfed, or cleated front interiors to provide nestling footholds.
  • No outside perches at the entrance holes that could aid predators.  

WARNING!  DON'T MAKE YOUR BOXES TOO SMALL!  









Many published box plans and boxes sold in stores are intended for bluebirds, which
although larger than swallows average fewer nestlings per brood.  In recent years
some bluebird hobbyists have advocated using very small boxes in a well-intended but
futile attempt to prevent box use by House Sparrows.  Don't use these boxes for
Tree Swallows!  They often have interior dimensions that are far too small for
swallow broods of up to seven young.  You may meet people who say the small
bluebird boxes are just fine for Tree Swallows, that swallows use them all the time.  
They are NOT ok!  While it is true that Tree Swallows will accept small boxes, their
nestlings may not thrive or fledge successfully.  Boxes with small internal volumes can
put nestlings at risk of death from hyperthermia (overheating) during hot spells.  
Smaller nestlings may get trampled by their larger siblings, have their feathers soiled
with feces, and be unable to reach food brought by parents.  Swallow nestlings also
require space to exercise their wings so they can fly strongly when they fledge.  It's
even possible that lack of space may interfere with proper bone development.  Plus
small boxes can also be detrimental to adult swallows.  Note the badly damaged wing
and tail feathers of the female swallow below that nested in a small box.  (Photo used
with permission of Charles G. Summers, Jr.).



















To avoid potential problems be certain your floors are at least 5" x 5".  
Narrow, cramped designs like the Peterson, Gilbertson, and Gilwood Bluebird Boxes
are totally unacceptable in a Tree Swallow project, and the North American Bluebird
Society and any of its member clubs and individuals that continue to promote the use
of boxes with small interiors show a disregard for the lives of other native songbirds.  

The same dimensions and standards apply if you purchase kits or ready-made
birdhouses.  If you plan to buy from a store, bring a ruler along.  Many of the boxes
you'll find will be too small for Tree Swallows (no matter what the clerk says).  If they
don't measure up (literally), don't buy!

And in case you were wondering, boxes designed for Tree Swallows are also very
acceptable for bluebirds: for many years 5" x 5" interiors were standard for bluebird
boxes.  There is one exception.  If you live in Mountain Bluebird range, make your
entrance holes just a bit larger, 1-9/16", if you want to try for both these bluebirds
and swallows.

Don't be afraid to improvise.
Since Tree Swallows are so very accepting in their choice of box designs you can be
creative, just as long as you follow the minimum size guidelines presented above.  
For example note the clever box below, designed and made by Irena of Ottawa,
Canada.  It features feeding holes that can be opened to prevent one large nestling
from monopolizing the food supply, a flip-up roof overlap, and a hinged side door.  It
is waterproofed on all outer surfaces except the front with candle wax, first rubbed
on and then melted in with a heat gun.  If you would like to try her design, click
here: IRENA'S SWALLOW BOX.











How many boxes should you build?
The best number depends on your habitat's quality, the size of your field, and your
energy and budget.  4 to 8 boxes is good for starters.  That's enough so you can see
how individual swallows vary in behavior and nesting, but not so many that record
keeping and box maintenance is a chore.  What the heck; if you want to start with
just one that's perfectly ok.  Just start.  If you enjoy your swallows you can always
expand next year.  Picture below from Jennifer Stanley.


















Click here for Next Step: Box Location.








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Building Boxes
Learn About Birds at Tree Swallow Nest Box Projects
NO!
Bluebird box
interiors too small!