Home range and habitat use of breeding common ravens in Redwood National and State Parks

Little is known about the space use of breeding Common Ravens (Corvus corax) in Redwood National and State Parks (RNSP) despite their identification as nest predators of the Marbled Murrelet (Brachyramphus marmoratus). We used radio telemetry to examine home range and habitat use of breeding Common Ravens in RNSP during 2009 (n = 3) and 2010 (n = 8). We estimated home range and core-use area size, calculated home range overlap between adjacent ravens, quantified site fidelity by calculating overlap between years for the same individuals, and used resource utilization functions to examine raven resource use within the home range. Average home range size of ravens in RNSP was 182.5 ha (range 82-381 ha) and average core-use area was 31.4 ha (range 5-71 ha). Home range use of individual ravens was generally higher near roads (n = 6), old-growth edge (n = 7), bare ground (n = 6), and in mixed hardwood (n = 5) and prairie habitats (n = 5). Use generally decreased near human use areas (n = 5) and in old-growth habitat (n = 5). While we found little overlap between adjacent ravens, the areas of overlap were centered on anthropogenic food sources that occurred at adjacent territory boundaries. Removal of anthropogenic food sources along roads and in human use areas within and adjacent to Marbled Murrelet nesting areas may reduce raven use of these areas and thereby reduce potential encounters of ravens and murrelet nests.