detect the models for what they are. The method may not work well because
model eggs are removed by predators and carried away. Attaching the eggs to
the nest with cord or wire to avoid this may affect the parents’ behavior.
Thorough pilot studies of the method are advisable if it seems to be the only way
to identify the causes of nest failure. The use of egg models is considered further
in Section 3.5.
3.4.3Cameras
Video or film cameras that are either triggered by events at the nest or take
a picture at fixed intervals (time-lapse) can be used to monitor nests and identify
causes of failure. Triggering of the camera by events at the nest using a passive
or active infra-red device or mechanical trigger is possible, but the activities of
the parent birds are likely to set the camera off frequently and this may over-
whelm the system’s capacity to store images. Successful use of time-lapse cameras
requires that the interval between frames is short enough that a predator cannot
visit the nest and leave between frames. This is sometimes no more than a few
seconds. Hence, time-lapse camera systems usually require considerable storage
capacity, for example, on videotape, and a substantial source of electrical power
to operate the recorder. Even then, it may be necessary to visit the system
frequently to maintain it and change batteries, films, or tapes.
At night, nests can only be monitored using low-light cameras or flash. The
use of infrared LED flash allows time-lapse cameras to be used throughout the
day and night without the flash affecting the behavior of parent birds or affecting
the behavior of predators (Pietz and Granfors 2000). However, checks should be
made that the flash is not emitting any light visible to them, by watching to see
whether they are startled when the flash fires.
The use of cameras can lead to biased identification of the causes of nest failure
in several ways. The cameras themselves are necessarily visible structures fairly
close to nests and may attract or repel predators and grazing animals in the
way that nest markers may do (see above). This problem can be reduced by
using camouflaged miniature cameras and by burying or otherwise hiding the
other equipment. Herranz et al. (2002) compared the daily failure rates of real
Woodpigeon Columba palumbusnests, artificial nests resembling those of this
species with and without automatic cameras and nests with camouflaged cam-
eras. The failure rate was lowest for artificial nests with uncamouflaged cameras,
with rates for the other groups being higher and similar to each other. This was
probably because predatory Magpies Pica picawere deterred from visiting nests
by the conspicuous cameras. If frequent visits by the researcher to the vicinity of
the nest are necessary to maintain the system, then these may attract or repel
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