see the tail of an incubating or brooding bird protruding over the edge of a nest.
Nests can be watched from a distance at the nestling stage and parents seen to be
taking in food or removing nestling droppings or the begging calls of nestlings
may be heard. If parents are seen at the nest and the stage of development of the
breeding attempt was estimated when the nest was first located, then there may
be no worthwhile additional information to be gained by disturbing the parents
to view the nest contents. For example, if the development of a clutch of eggs was
not assessed when a nest was first found, it might be considered necessary to dis-
place a sitting parent bird at the next check to see whether hatching had occurred.
However, if the stage assessment indicated that the eggs were unlikely to have
hatched, it is sufficient to see the parent sitting on the nest to know that the
attempt has not failed. Assessment of developmental stage can also be used to
time nest checks to coincide with events of particular interest, such as hatching
or the age at which young can be safely removed from the nest for ringing. This
often allows the number of checks to be reduced. Other precautions to reduce
the risk that nest checking will draw the attention of predators to the nest include
walking to and from the nest by different routes so that the nest is not at the
end of a track, restoring trampled vegetation, avoiding touching the nest, and
visiting and looking at apparently suitable nest sites where no nest really exists
so that predators watching or tracking the researcher are not always rewarded
when they visit the same places. Martin and Geupel (1993) provide useful detail
on these precautions.
It is important to record what is actually seen during nest checks, as well as
what is inferred to have happened. It is good practice to prepare a list of signs that
may be seen during a nest check and to know what can reasonably be inferred
from them. This is especially important for the nest check at which it is discov-
ered that there are no longer eggs or nestlings in the nest. For birds with precocial
young, an empty nest that might have hatched or failed should be checked care-
fully for the small fragments of eggshell that fall into the nest cup when the chicks
are chipping the shell open during hatching. Shell remains are taken away or
eaten by the parents after hatching in some species including waders and, for
these the chippings may be the only clue that hatching occurred. In other species,
including many waterfowl, galliform birds, and rails, hatched shells are left in the
nest and are distinguishable from damaged shells left by predators by the way the
shell has opened. Hatched galliform eggs tend to have a circular cap removed at
the blunt end of the egg. The texture of the shell membranes of hatched eggs
is brittle and papery especially where shell fragments became detached from
the membrane during hatching, whereas the membranes of depredated eggs
are usually flexible and adhering to the shell. Alarm calls or distraction displays
Measuring the success of individual breeding attempts| 63