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 cavity, natural or man-made, they can get into.
- Tree Swallow nests have been found in large boxes meant for Purple Martins,
Wood Ducks and Screech Owls, and in such unlikely spots as drain pipes,
mailboxes and newspaper tubes (photo below by Laura Niang in Maryland).
- Sadly, they'll also try to nest in tiny or flimsy boxes where few young survive.
Be sure to build boxes designed specifically for Tree Swallows.
- You'll want boxes built carefully of good materials, where your swallows will be
safe from predators and protected from rain and cold, and also from heat; ones
roomy enough so parent swallows can raise strong, healthy young.
WE RECOMMEND THE FOLLOWING TWO TREE SWALLOW DESIGNS:
- Click this link for the plan of the GOLONDRINAS BOX. This box (see below) is
easy to make and is used by scientists of the Golondrinas de las Americas
(Swallows of the Americas) project coordinated by Cornell University.
- The Golondrinas project is a unique hemisphere-wide effort conducting research
into the comparative biology, ecology, and behavior of Tree Swallows and the
eight other species in genus Tachycineta.
- Thousands of Golondrinas Boxes are in use at the 50 or so research sites
throughout North and South America (see map).
- If you decide to make Golondrinas boxes we have two suggestions. Make the top
wider and longer for increased protection against bad weather and predators,
and be ready to block the ventilation openings on the upper sides during cold
windy and rainy spells (see below).
- Click these links 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
harder to make, but we've used it at Salmon Creek since 2003 and are very
- 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 plywood (exterior-grade
only) 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 not 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 OR BUY BOXES THAT ARE 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.
- Recently some bluebird hobbyists have advocated using very small
boxes in a well-intended but futile attempt to prevent box use by House
- DON'T use these boxes for Tree Swallows! They have interior
dimensions that are far too small for swallow broods of up to seven
- You may meet people who say the small bluebird boxes are just fine for Tree
Swallows. They are NOT ok! While it is true Tree Swallows will eagerly accept
small boxes, their nestlings may not thrive or fledge successfully.
- Boxes with small internal volumes put nestlings at risk of death from overheating
during hot spells because the nestlings can't spread out to cool.
- Smaller nestlings may get trampled by 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, and it's possible lack of space may even interfere with
proper bone and feather development.
- Imagine six or seven swallow nestlings trying to survive in the tiny bluebird tube
below! (Photo from Craig A. Mullenbach of Mully410*Images*).
- Nest boxes with small interiors can also be detrimental to adult swallows.
- Note the badly damaged flight feathers of the swallow below that nested in a small
bluebird box. (Photo by 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, Gilwood, and Troyer
Bluebird Boxes are totally unacceptable for Tree Swallows.
- We are sorry to say this but In our opinion 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 blatant disregard
for the survival of other native cavity-nesting 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.
- As you search for boxes you may find miniatures for sale, such as the one below
in Sarah Rosedahl's photo. Although cute, these boxes are not remotely roomy
enough for proper development and survival of Tree Swallow broods. Buy and
display these boxes for their decorative value if you wish, but please don't put
them out intending to attract nesting Tree Swallows, and if you do find swallows
investigating, replace these boxes with suitably-sized ones.
If you're not convinced yet that nest boxes with small interiors are detrimental
for Tree Swallows please compare the four nest box floors below.
- Which of the above boxes would provide enough space for the typical brood of
six swallow nestlings shown? These youngsters are only twelve days old and
must develop inside their nest box for another six to ten days before fledging.
How many would you think could survive in the two bluebird-type boxes?
But why would Tree Swallows even attempt to nest in tiny cramped boxes?
- We really don't know why. They certainly don't seem to use "selective
judgement" in their choices.
- The shortage of natural cavities probably drives Tree Swallows to accept anything
they can claim. But knowing swallows will use them we have a responsibility
never to offer them bluebird boxes that are nothing more than miserable little
- And what about bluebirds? They're larger than Tree Swallows! How
could boxes with small interiors possibly be good for bluebirds? Click
here to read Linda Violett's excellent treatment of this subject.
- The fact is that the large-interior box designs we recommend for Tree Swallows
are also very acceptable for bluebirds, (provided the entrances are made at least
1-1/2"), and please be aware that for many years 5" x 5" interiors were the
standard recommendation for bluebird boxes.
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
- 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.
Consider installing a Nest Camera inside a box.
- Tree Swallows are so easy to watch we sometimes forget many vital behaviors
and actions occur inside their nesting cavities. But the advent of tiny remote-
control cameras presents you the opportunity to view even those.
- We have never used nestcams ourselves, but we know persons who have
enjoyed them tremendously, who've spent many fascinating hours observing live
video on their TV's or computers as their swallows built nests, incubated eggs
and raised young.
- To get a sense of what can be seen using nestcams click here for the Cornell
Lab of Ornithology's NestCam site. Be sure to visit Explore Archives.
- To learn about nestcam hardware and installation click here for the bluebird
hobbyist web site Sialis' excellent page on the subject.
- Be aware you may have to tweak your box design to accommodate a nestcam.
Buying Boxes is always an option.
- If you do prefer to buy a box consider the BIRD BROS BOX, pictured below,
designed specially for Tree Swallows by Chris Janelli and Peter Becket, in
association with Bingham Brook Farm of Vermont.
- In 2015 we tested a version of this box at Salmon Creek, and it was used very
- Glenn Foote of Nova Scotia builds a CEDAR TREE SWALLOW NEST BOX that
meets all pertinent specifications for this species. His box, seen below, can be
- And Purple Martin gourds, both natural and artificial, usually have plenty of room
for Tree Swallow families, as the youngsters in Charlie Kelley's photo from
- If you decide to use martin gourds be sure the entrance is too small for European
Starlings to pass. Many types of Starling blockers are sold for artificial gourds.
Natural gourd entrances should be cut at 1-1/2" or 1-3/8".
How many boxes should you build or buy?
- The best number depends on your habitat's quality, the size of your field, and
your energy and budget.
- 3 to 5 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.
- But if you want to start with just one that's perfectly ok. Just start. If you enjoy
your swallows (and we know you will) you can always expand next year. Picture
below from Jennifer Stanley in Kentucky.
Click here for Next Step: Box Location.
Learn About Birds at Tree Swallow Nest Box Projects
interiors too small!
|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