VAN BERGEN VS, RIEM VIS R, BRINKGREVE J, STELMA J & NIJLUSING W (2021) Parental care by a pair of Honey Buzzards Pernis apivorus: investments in reproduction, survival and predation risk, assessed by monitoring nests with camera traps. LIMOSA 94 (3): 89-100.

In raptors with biparental care but sex-specific roles, adults are facing a trade-off between food provisioning and protection of the brood at the nest against predation and adverse weather. We followed the breeding cycle of a pair of Honey Buzzards in the north of the Netherlands with camera traps at their nest sites in 2015 and 2016. We monitored nests by using two different camera trap settings: the time-lapse function (camera programmed to take one picture every minute) and motion trigger function (camera programmed to take one picture in response to movement). To determine nest attendance and prey delivery, we used one camera with the time-lapse function in 2015 and two cameras in 2016 (one with the time-lapse function and one with the motion trigger function). The consecutive nests in 2015 and 2016 were 4.2 kilometres apart. In both years, the female incubated the eggs about two-thirds of the time. In 2015 the nest had two chicks, that were both depredated by a European Pine Marten Martes martes at 8:28 AM local time when the oldest chick was 27 days old. In 2016 only one of the two eggs hatched, and the nestling fledged successfully. Adult nest attendance was lower in 2015 during the nestling phase as compared to 2016, especially shortly before the brood was depredated (Fig. 1 and 2). We propose that the higher food demand and possibly lower food availability in 2015 caused the female to more often assist the male in hunting. This resulted in lower nest attendance and a consequently higher predation risk. Common Wasp Vespula vulgaris was the most frequent prey in both years, resp. 29.4% and 43.5% (Appendix 1 and 2). Prey were better identified by the motion trigger camera trap than by the time-lapse camera trap. Like in most raptors, usually the male brought prey to the nest while the female provided the young with direct care at the nest. In 2016, the female visited the nest for the last time when the chick was 45 days old. The male appeared for the last time on the nest when the chick had an age of 54 days. For monitoring nest attendance and prey delivery rates, we advise to use one camera trap with a combination of the time-lapse (one picture per minute) and the motion trigger (three pictures with a three seconds interval and a 'quiet period' of five minutes) function, with the time-lapse function off during the night time. With these settings, camera traps continued working for 10 to 14 days on one set of batteries, collecting the maximum amount of information.

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