A Device to Record the Specific Time an Artificial Nest is Depredated
High levels of nest depredation reduce the nesting success of many bird species (Klett et al. 1988, Howlett and Stutchbury 1996, Pitman et al. 2006, Franzreb 2007, Perkins and Vickery 2007). For this reason, many studies have investigated nest depredation patterns. Artificial nests frequently are used to evaluate the effect of nest density, egg color, vegetation structure, odor, nest concealment, clutch size, seasonal and landscape characteristics, and other factors on nest depredation (Sugden and Beyersbergen 1986, Major and Kendal 1996, Jobin and Picman 2002, Conner and Perkins 2003, Ackerman et al. 2004). Although artifi cial nests allow for a more rigorous experimental design than observational studies on natural nests, argument continues over the utility of artificial nests, given that predation rates between natural and artificial nests oft en diff er (see Faaborg 2004, Moore and Robinson 2004). Estimating nest survival rates can be problematic in both natural and artificial nesting studies. Frequent visitation of nests by investigators can increase depredation rates (Major 1990, Esler and Grand 1993), but longer periods between nest visits reduce accuracy in determining when these events occur. Knowing the exact time and date of depredation events without having to make frequent visits to the nests, investigators could learn more about predator activity patterns and the factors that influence predator foraging behavior. We modified a nest-timer design by Ball et al. (1994) to create a device that recorded both the calendar date and time of a depredation event on an artificial nest. Additionally, our timer was easier to construct than Ball’s because it involved only altering the wiring to the battery and, unlike the design by Ball et al. (1994), our timer did not necessitate locating the clock’s oscillating crystal. We also developed a method to stabilize the trigger, thus minimizing conspicuousness of the device at the nest site. The purpose of this paper was to describe how to make the device and evaluate its effectiveness.
J.S. Borgo, M.R. Conover. 2009.A device to record the specific time an artificial nest is depredated. Human Wildlife Conflicts. 3(1):88-92