Dawson, I / February 1989 – vol. 82, issue 2, pp 70–71 Items included in this feature have been submitted by the manufacturers or their agents. The reviews are the personal opinions of the reviewers; they are not the result of technical tests, but are assessments made after use in appropriate conditions (e.g. in the field). Neither British Birds nor the individual reviewers can accept responsibility for any adverse consequences of opinions stated, and... This article is only available to registered users.To read more, please log in or purchase a subscription.