What is a box check?
- A box check is a brief examination of a box's contents, recording what's seen on
a data sheet.
- Most Box Check Record sheets (click link to see example and also see
example below) have fields for date, time, box number, species using the box,
stage of nest construction, number of eggs, number of young, and remarks.
- Using codes or abbreviations 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 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, usually anchoring
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. Some may even 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 do so very carefully. These
- 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 at night may 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 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
- 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
!/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
Learn About Birds at Tree Swallow Nest Box Projects