Effects of low-level jet aircraft noise on the behaviour of nesting osprey

1. Nesting osprey Pandion haliaetus L. were exposed to controlled low-level CF-18 jet aircraft overflights along the Naskaupi River, Labrador, Canada, during 1995. Jet aircraft flew near five nests at distances ranging from 2·5 nautical miles (nm) to directly overhead at speeds of 400–440 knots.
2. Maximum noise levels (L1) and other noise metrics were influenced by many factors including topography, distance, altitude, wind speed and direction.
3. Based on 240 h of observations from blinds, we recorded osprey nest attendance and egg exposure during 139 individual overflights. Similar observations were completed at two control nests. Overflights as low as 30 m above ground occurred during incubation, nestling and prefledging only when observers were present.
4. Osprey behaviour did not differ significantly (P = 0·126) between pre- and post-overflight periods. Despite L1 values occasionally exceeding 100 decibels, adult osprey did not appear agitated or startled when overflown.
5. Osprey were attentive to and occasionally flushed from nests when float planes, other osprey or raptors entered territories, and when observers were entering or exiting blinds.