Estimating the productivity of colonial waterbirds can have important conservation and management implications. For tree-nesters, investigators must climb nest trees to obtain productivity data. In this study, we employed indirect inspection of nest status by using a pole-mounted camcorder at 77 nests in five colonies of tree-nesting grey herons Ardea cinerea in northern Poland. We found no significant relationship between the time spent recording per nest and the age or height of the inspected trees. We found that nestlings did not react to the presence of the climber manipulating the polemounted camcorder. However, we did record visible reactions from small chicks (< 4 weeks old) to the presence of cameras close to the nest, including threat poses and upright, forward and snap displays. For older nestlings (= 4 weeks old) we recorded only threat postures. This novel method allows the collection of ecological and/or behavioural data that cannot be obtained by observation from the ground, for example, the presence of eggs and small chicks, food or dead nestlings. Our study demonstrates that pole-mounted camcorders are a good alternative to nest climbing if there is no need for direct contact with nestlings. This method also reduces the duration of disturbance and is also safer for the climber.
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