Detecting, but not affecting, nest-box occupancy

Abstract

Context. Nest boxes are a useful tool in the reintroduction, conservation and monitoring of many hollow-using species. Aims. All forms of nest-box monitoring involve some form of invasion, often upsetting their continued use by occupants. We conducted a pilot study to investigate and validate the innovative use of temperature dataloggers (iButtons®) to remotely monitor nest-box use, leaving the nest-box occupants untouched. Methods. In captivity, iButton recordings revealed the duration and time of day when each of the three nest-box designs was occupied by Pseudocheirus occidentalis (western ringtail possums); the accuracy of occupancy data was validated by unobtrusive infrared video recording. In the field, where translocated P. occidentalis and naturally occurring Trichosurus vulpecula (common brushtail possum) populations are present, hair sampling at the nest-box entrances (in addition to iButton recording) was used to identify the mammal species present. Key results. Nest-box use by captive P. occidentalis validated iButtons as a useful remote-monitoring tool, with <5–6% error for two nest-box designs. Although there was limited use of nest boxes at the field site, our results confirmed that iButtons are useful for remote-monitoring of nest-box use in the field; iButton data revealed both short (<2 h) and long (>10 h) periods of continuous occupancy (T. vulpecula only). In addition to the convenience (to researcher and animal) of continuous (24-h) monitoring with minimal disturbance, a major advantage from using iButtons is that occupancy can be matched with environmental temperature or rainfall records, as well as other events (e.g. storms or frost). Conclusions. iButtons are a useful remote-monitoring tool of nest boxes, and it is possible that their use in this manner may be extended to tree-hollow occupation. Most importantly, this approach can inform us as to the conditions under which the nest boxes are used by fauna, as well as preferences for different nest-box designs. Implications. It is important to note that the criteria used for determining the presence or absence in the nest box (i.e. temperature difference, Tin– Tout, of 2°C) in the present study will not be relevant for all nest-box designs and before using these methods, the thermal properties of the nest box or tree hollow will require investigation.