Using motion-activated cameras to study diet and productivity of cliff-nesting Golden Eagles

Studies of cliff-nesting raptors can be challenging because direct observations of nest
contents are difficult. Our goals were to develop a protocol for installing motionactivated
trail cameras at Golden Eagle (Aquila chrysaetos) nests to record diet
information and productivity, and to estimate prey detection probability using different
diet study methods. In 2014 and 2015, we installed cameras at 12 Golden Eagle nests
with 18—42 d old nestlings. Following installation, we monitored adult behavior from
direct observation and post-installation image review. At two nests, adult eagles did
not return to nests or exhibited behaviors suggesting avoidance of the cameras, but
returned to the nests after cameras were removed. We visited the ten remaining nests
every 4 d to collect prey remains and pellets to generate prey-specific detection
estimates for both images, and prey remains and pellets. Compared to inspection of
prey remains and pellets, cameras recorded twice the number of prey (622 vs. 316),
were more likely to detect the smallest and largest prey, and cost half as much.
Cameras recorded productivity, fledging dates, and in one case, a nestling death. Trail
cameras may be a reliable and cost-effective option to address clearly defined
research goals and obtain required information about eagle behavior and nest
contents. However, cameras should be used judiciously because installation creates a
persistent manipulation at the nest. Camera appearance should be minimized, and
post-installation monitoring that allows for timely responses to nest avoidance behavior
by adult eagles is important to prevent adverse effects on nesting success.