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, both 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.


  • Click this link for the plan of the GOLONDRINAS BOX.  This box (see below) is
    easy to make and is the preferred box of the 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 plans in  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
    considerably harder to make.  
  • We have used Long Point boxes at Salmon Creek for years and had been very
    satisfied.  However, in 2019 we learned that a trial conducted in Saskatchewan
    comparing Long Point and Golondrinas boxes found nestlings being raised in the
    latter box rated higher on several measures of body condition.  The researchers
    attributed this to cooler box interiors and less dramatic temperature fluctuations.  
  • We still believe Long Point boxes are better than most Tree Swallow box designs,
    but in light of the above findings we suggest that persons planning to build boxes
    choose the Golondrinas, especially where high temperatures are expected.   

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) no less than 1/2" thick, preferably thicker.
  • 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 or unstained interiors.
  • Roughened, kerfed, or cleated front interiors to provide nestling footholds.
  • No outside perches at the entrance holes that could aid predators.  


  • 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 interiors 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.  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 caused by her
    nesting in a small bluebird box.  (Photo 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, 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?
  • Are you still not convinced small interiors can be detrimental for Tree swallow
    nestlings?  If so, please watch these two YouTube videos of six nestlings crowded
    into a box whose 4.5 " x 4.5" interior is actually 27% larger than the 4" x 4"
    bluebird box above and 38% larger than the 4" diameter bluebird tube.
  • Video 1 shows nestlings 15 and 16 days old.
  • Video 2 shows nestlings 18 days old, the day before they fledged.
  • After having watched, ask yourself why anyone would ever deliberately offer
    anything even smaller than the box in the videos to their swallows?

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
    death traps.
  • 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
  • Before ending this discussion of space we want to commend Purple Martin
    hobbyist organizations which now urge members to use larger compartments in
    their martin housing.  We wish bluebirding groups would do the same.

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 prefer to buy a box Duncraft offers at least two varieties.  We have tested
    model #2107, seen below, successfully.

  • Glenn Foote of Nova Scotia builds a CEDAR TREE SWALLOW NEST BOX that is
    spacious, hand-crafted of high-quality materials, and thoughtfully designed to
    incorporate many other features known to be beneficial for this species.  His box,
    seen below, can be purchased online by e-mailing g2foote@gmail.com.

Another Option: Purple Martin Gourds.
  • We've begun experimenting with artificial Purple Martin gourds sold by S & K, with
    good results.  They are inexpensive, very roomy and some models come with
    Tree Swallow-size entrance holes.
  • We did modify our gourds, adding S & K "tunnels" in which we cut Tree Swallow-
    sized openings, and removing porches and wing entrapment pieces (see below).
  • Click Here to learn how to modify martin tunnels in order to add an extra
    measure of predator protection to Tree Swallow boxes and gourds.

  • Natural martin gourds are also accepted by Tree Swallows, as the youngsters in
    Charlie Kelley's photo below from Alabama demonstrate.
  • However, if you decide to use any martin gourds be certain the entrances are
    sized for Tree Swallows, with either narrow slots or round entrances no larger
    than 1-1/2" in diameter.  Larger openings may admit Starlings.  

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: Where to Locate Tree Swallow Nest

Building or Buying Nest Boxes
for Tree Swallows
Learn About Birds at Tree Swallow Nest Box Projects
Bluebird box
interiors too small!