As is often repeated in these pages, birds’ calls are often vital in identification. This applies very much to terns, many of which are pretty vocal birds. Perhaps the most useful call to learn is that of the Sandwich Tern. Their distinctive, loud, rough ‘ kirrick ’ calls are often the first sign that there are Sandwich Terns around, being audible for some distance. This is particularly useful for inland patch workers, for whom terns such as Sandwich are ‘patch gold’.