Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Individual study: Impact of ringed-billed gull Larus delawarensis control on common terns Sterna hirundo nesting on Ice Island, upper St. Lawrence River, Ontario, Canada

Published source details

Blokpoel H., Tessier G.D. & Andress R.A. (1997) Successful restoration of the Ice Island common tern colony requires on-going control of ring-billed gulls. Colonial Waterbirds, 20, 98-101

This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Reduce inter-specific competition for nest sites of ground nesting seabirds by removing competitor species Bird Conservation

A before-and-after study from 1989-1996 in the upper St. Lawrence River, Canada (Blokpoel & Tessier 1997) found that excluding ring-billed gulls Larus delawarensis from a 0.17 ha island increased the number of common terns Sterna hirundo from zero in 1989 to 135 pairs in 1993 (compared with 121 pairs in 1976 before gulls colonised the island). Monofilament lines (70 cm apart over approximately 60% of the island), combined with destroying gull nests and eggs during 1990-3, reduced the number of gulls breeding from 181 pairs in 1989 to zero in 1990 and 1991. The exclosure was not erected in 1994-6 and fewer gull nests were destroyed, leading to a recovery in gull numbers from two (1994) to 250 nests (1996). Tern numbers remained high in 1994-5 (141 and 149 pairs) but fell to three pairs in 1996.


Use decoys to attract birds to safe areas Bird Conservation

A before-and-after study in the upper St. Lawrence River, Canada (Blokpoel et al. 1997) found that a common tern Sterna hirundo colony was re-established when decoys as well as control of ring-billed gulls Larus delawarensis were used to try to attract birds. This study is discussed in ‘Reduce inter-specific competition for nest sites by removing or excluding competitor species’.