Forest Landscape Patterns around Marbled Murrelet Nest Sites in the Oregon Coast Range

Abstract

We analyzed forest composition and landscape preferences of marbled murrelets (Brachyramphus marmoratus). Using dawn surrreys and tree climbing, we found 41 murrelet nest sites on state and federal lands in the Oregon Coast Range Province in western Oregon between 1990 and 1998. Landscapes in 0.5- and 1.0-km-radius plots at these nest sites were compared to patterns in similar plots around a set of points randomly selected from stands of mature or old- growth trees on public lands in the same province. We found less open-sapling and hardwood forests in the plots at nest sites than at random sites for both plot sizes. Conversely, the pro- portion of pole-young conifer habitat was greater at nest sites than at random sites for both plot sizes. Landscape pattern analysis showed that the amount of edge-perimeter density, nest-patch perimeter, and high-contrast edge of nest patches was lower in the 1.0-km-radius plots at nest sites than at random sites. Our best multivariate logistic regression model indicated that greater amounts of pole-young and mature-old-growth forests, less edge (perimeter density and high- contrast edge at nest patches), and more cohesive nest-patch shape best distinguished murrelet nest sites from random sites. We hypothesize that murrelet nest-site selection at the landscape scale may be the result of an antipredator strategy to reduce predation risks on eggs and juvenile murrelets. Young (simple-structure) conifer stands adjacent to nesting areas may decrease pre- dation rates at murrelet nests. Land managers should consider limiting clearcut harvest units both adjacent to murrelet nest patches and within at least 1 km of murrelet nests, as clearcuts increase high-contrast edge in addition to increasing fragmentation levels.