Set-Back Distances to Protect Nesting and Roosting Seabirds Off Vancouver Island from Boat Disturbance

Abstract

Recreational boat traffic is increasing worldwide and there is a need for scientifically based regulations that sustain both seabirds and wildlife viewing. The effects of boat disturbance to seabirds off Vancouver Island, Canada were quantified by testing distances that roosting or nesting birds showed an agitation response to an approaching motorboat or a kayak. The effects of species sensitivity, vessel type, habituation and season on agitation distance were examined. At 40 m from approaching boats, nesting Double-crested (Phalacrocorax auritus) and Pelagic (P. pelagicus) cormorants, Black Oystercatchers (Haematopus bachmani), Glaucous-winged Gulls (Larus glaucescens), and Pigeon Guillemots (Cepphus columba) had less than 6% probability of being agitated with either a kayak or motorboat, while at 50 m there was less than 2% probability of agitation. Roosting birds had larger response distances than nesting birds. Roosting Harlequin Ducks (Histrionicus histrionicus) were particularly sensitive with 24% probability of agitation at distances less than 50 m. Agitation distances were reduced by habituation to boat traffic and a single kayak could approach closer than a motorboat without disturbing seabirds. A general set-back guideline of 50 m would protect most nest and roost sites while allowing viewers to appreciate seabirds. Setbacks could be adjusted to protect locally sensitive sites or species.