Raptor Use of Artificial Perches in California Rangelands in Fall

Abstract

Author(s): Kross, Sara; Chapman, Renata; Craig, Andrea; Kelsey, T. Rodd | Abstract: Most raptor species rely on perches for hunting, resting, preening and roosting and in many agricultural areas the availability of adequate perches can limit raptor abundance and diversity. This has negative implications for both raptor conservation and the natural pest control services they can provide for farmers. Installing artificial perches on agricultural lands can therefore benefit both raptors and farmers. However, installing perches under current guidelines is difficult on California’s 38 million acres of rangelands, where rocky soil can be restrictive to anchoring poles belowground. We developed a novel method for modifying existing fenceposts to support raptor perches. These raptor perches are relatively light, easy to construct, can be transported in multiple pieces and assembled in the field. We installed 16 artificial raptor perches in four representative habitats on a California ranch to 1) determine if raptors will use artificial perches in each habitat; 2) test raptor preferences for different perch configurations; and 3) observe which raptor species utilize perches. Here, we share our perch design as well as our results from monitoring perches between August and November 2017. We found that American kestrels, great horned owls, barn owls, and red-tailed hawks utilized perches, as did a number of non-raptor species. Perch use by raptors was highest in an irrigated pasture and at a mid-elevation grassland site located on a hill. Perches at a low-elevation, unirrigated pasture with no slope and perches located in higher elevation oak woodland sites were used significantly less. In all habitats raptors preferred to utilize 15-foot perches over 20-foot perches. Raptors rarely utilized a lower perch when two were available on a single pole, suggesting that this added feature is not necessary to attract the species we observed.