What is a Tree Swallow box check?
  • A box check is a brief monitoring opening of a nest box to examine its contents,
    and then recording what's seen on a box check record sheet.  Box checks can,
    of course, be used for nesting attempts of other bird species.
  • Most Box Check Record sheets have fields for date, time, box number,
    species using the box, nest construction stage, number of eggs, number of
    young, and remarks.  Click link above to see example and also see below.
  • Using codes or abbreviations for data makes recording easier.

How do you check a box?
  • Approach the box quietly from the side.
  • Unfasten the door gently and open it just enough to peek inside.
  • If there is an adult swallow inside close the door carefully and move on to
    another box, making a note to return to this box later.
  • If there is no adult inside open the door wide enough to view the whole interior.
  • Note pertinent box contents data on the Box Check Record sheet.
  • Any broken eggs or dead nestlings you find should be removed and disposed of
    well away from the box.
  • Refasten the door securely and move on.

Warning!  Some types of colonial wasps build nests in birdhouses, anchoring their
nests on the underside of the roof.  Make it a habit to check for wasp nests so they
can be removed while they are small.  Rubbing the attachment surface with a bar of
soap helps deter wasps from building.

Won't opening boxes disturb the swallows?
  • They clearly aren't pleased to have you poking in their nests, which is one
    reason to make checking boxes the last thing you do on a project visit.
  • They may give alarm calls, attracting a crowd, and some may dive on you, but
    Tree Swallows almost never desert a box that's simply been checked.  

However, there are a few situations when Tree Swallows are sensitive to
disturbance, when you should not open boxes or if you must, do so very
carefully.  These are:
  • On mornings when females are laying eggs wait until after 9:00 A.M.
  • During incubation, open the box a crack and peek in to make sure the female is
    not inside before making a full check.   If the female is inside, close the box,
    back away and wait until she leaves before checking.
  • Don't ever check boxes at night!  Females disturbed after dark could desert,
    even if they are incubating eggs or brooding small young.
  • Don't open a box with nestlings older than 12 days, unless you must in
    order to control parasitic mites.  Disturbing older nestlings could cause them to
    jump out of the box prematurely, fall to the ground, and die.  
  • Look carefully at the wing of the 12 day old nestling below.  Note how the
    flight feathers of the wing have partly erupted from their sheaths and resemble
    little paintbrushes.  
  • If you don't know the exact age of the nestlings in a box, and you find
    ones with wing feathers more erupted than in this example, leave them
  • If you take these precautions box checks shouldn't endanger your birds.

How often should you make box checks, and how do you know when a box
has laying or incubating females, or when nestlings are 13 days old or older?
  • It's best to make box checks at least once a week, the more often the better
    since there are some crucial events, such as last egg date and hatch date, it's
    important to know.
  • Early in the season you would normally check every box on each visit to your
  • However, once a female has finished laying her eggs it's best to rely on your
    Control Sheet  to guide checks at that box.  
  • The Control Sheet displays the status of every nest so you'll know which boxes
    need checking and when, so unnecessary checks and potential problems can
    be avoided.  Refer to your Control Sheet at home before visits.  

Box Check data fields:
  • Date and Time:  Some people omit time.
  • Box Number:  You should have a numbering system for your boxes.  It helps to
    have numbers marked on the box doors.  Note: You may not need to check
    every box on every visit.  Your Control Sheet helps determine exceptions.
  • Species:  You can use the banders' four-letter code.  For instance; Tree
    Swallow = TRES, Eastern Bluebird = EABB, House Wren = HOWR, etc.
  • Nest:  Stage of nest construction measured in shape and completeness of cup
    vegetation, and amount of feathers.  These are all rather subjective, but let you
    compare nests.  (Note: It's common to stop noting nest construction data once
    eggs are laid).
    MT = empty box
    FG = few grasses or other vegetation
    1/4 C = ring of vegetation hardly visible
    1/2 C = ring visible
    3/4 C = nest cup is shaped but box floor still visible
    CC = complete nest cup formed and box floor covered  
    FF = few feathers
    SF = some feathers
    MF = many feathers
    VMF = very many feathers       
  • Eggs:  Number of eggs present.  Tree Swallows lay one egg per day, but
    sometimes if weather is poor females skip a day.  A skip of several days usually
    means another female has taken over the nest and has started to lay her own
    eggs.  Takeover females often lightly cover the eggs of the previous female.  
    Occasionally one or more eggs are thrown out by competitors, either other
    swallows or competing species.  Note: you may have to remove eggs one at a
    time to get an accurate count.  Lift them very carefully, place them in a cupped
    hand, then replace them gently in the cup.
  • Young:  Number of young present.  As with eggs you may need to remove
    young to get an accurate count.  Ease your fingers carefully underneath each
    one at a time, lift it out, and place it into your other hand.  If they grab nest
    material in their feet give them a minute to relax their grasp.  Older nestlings can
    be squirmy.  Don't drop!  Be sure to replace nestlings directly into the nest cup,
    not out on the edges, and return them to the cup very gently so they aren't
    injured by hard pieces of vegetation.
  • Remarks:  You might want to note dead or missing eggs or young, runted
    young, behavior of adults during the check, takeover concerns, presence of
    wasps, unusual nest material, weather issues, etc.

What do you do with all this data?
  • You take it home for transfer into the Nest Box Record sheets you keep for
    each box.

Tree Swallow Box Checks and Recording Box Check Data
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