Ratcliffe et al. (2006) compared the breeding biology of terns Sterna spp. on the Uists, Western Isles, where American Mink Mustela vison (hereafter ‘mink’) had been removed, and on nearby Lewis, where there had been no mink control. They showed that hatching success was significantly higher on the Uists, indicating that mink removal improved this aspect of breeding, but found no significant difference in colony productivity between the two areas. The years in which the comparisons were made, 1993 and 2005, were years of low tern productivity, probably caused by poor weather and food shortage, respectively. The authors considered that such factors overrode any effect of mink by killing young terns before mink could take them, and suggested that any effects of mink would be more detectable in years of high tern productivity when more young terns survived.

I am most grateful to Norman Ratcliffe, Ian Mitchell and Martin Heubeck for comments and corrections to earlier drafts of this note, and to the many people in the Argyll area who have helped with mink control and seabird counting over the years. I particularly thank Rob, Audrey and Niall Lightfoot and the late Ian Hynd.

Birks, J. 1986. Mink. The Mammal Society, Anthony Nelson, Oswestry.

Craik, J. C. A. 2000. A simple and rapid method of estimating gull productivity. Bird Study 47: 113–116. [Crossref]

Craik, J. C. A. 2008. Sex ratio in catches of American Mink – how to catch the females. Journal for Nature Conservation 16: 56–60. [Crossref]

Ratcliffe, N., Houghton, D., Mayo, A., Smith, T. & Scott, M. 2006. The breeding biology of terns on the Western Isles in relation to mink eradication. Atlantic Seabirds 8: 127–135 [published April 2008].