Predation on Artificial Nests in Forested Riparian Buffer Strips

Abstract

We used artificial nests to examine predation in riparian buffer strips created by commercial clear-cutting and in unharvested control areas on industrial forestlands in eastern Maine. Nests in riparian buffer strips were depredated more often than those in intact riparian forests. This pattern was similar for both ground and shrub nests and for both trials. Predation rate for nests in control stands was 15%, compared to 31% in 20-40m wide buffer strips along tributary streams (P = 0.016) and 23% in 60-80m wide buffer strips along mainstem streams (P = 0.045). Predation rates were similar (P = 0.41) in mainstem and tributary buffer strips. Greater predation rates documented for nests in riparian buffer strips likely resulted from an elevated number and diversity of predators associated with the narrow, linear forest stands. Remotely-triggered cameras placed on a subset of nests revealed 6 species of nest predators. Predators identified at nests were mostly forest species and not species directly associated with riparian habitats. Red squirrels (Tamiasciurus hudsonicus) and blue jays (Cyanocitta cristata) were responsible for >50% of the identified depredations. Black bears (Ursus americanus) were photographed only in tributary buffer strips and may have been using them to travel between larger forested stands. Increased predation of eggs and young probably reduces the nesting success of birds in riparian buffer strips. Managers should leave wide (≥ 150-m) buffer strips along riparian zones to reduce edge-related nest predation, especially in landscapes where buffer strips are an important component of the existing mature forest.