Pilot studies

Harris et al. (1990) noted the importance of a pilot study when collecting location data. Before embarking on extensive work, it is wise to check techniques for capture, tagging, and data collection. Can the animals be marked without bias? Tagging nestlings is likely to minimize bias compared with trapping techniques that may select poor quality individuals. Tests for tag impacts can start with simple behavioral comparison with untagged birds, ideally in captivity and remembering that animals may always require a day or two to adjust to handling and tagging. How large a sample can be monitored in the field? That will depend on how easy it is to check individuals and move between them, which will improve with practice. A pilot study helps the pessimist to be more ambitious in a main study, and the optimist to avoid over-ambitious planning.

A pilot study should also address the issue of how often to monitor animals, typically by deliberate over-sampling so that analyses can define a minimum-effort protocol. That may mean that initial tracking is continuous, recording the location and time each time a bird feeds or flies, developing field skills to avoid disturbance and gaining behavioral insights that aid later work. This showed, for instance, that released naïve hawks were likely to survive once they had made 2—3 kills (Kenward et al. 1981). Continuous monitoring also reveals when animals are likely to be active, so that foraging observations can be planned for those times. Activity data can also be recorded by automated logging, for instance while tracking every hour to collect location data from 5—6 animals (i.e. a minimal sample for statistical tests).

For a study over more than 1 year, pilot work should also involve recording locations at 3 to 4 day intervals. This is convenient for recording dispersal and survival data, and for indicating the seasons in which animals tend to settle.

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