Experimental measurement of nesting substrate preference in Caspian terns,Sterna caspia, and the successful colonisation of human-constructed islands (vol 85, pg 63, 1998)

Caspian terns, Sterna caspia, recently bred in Hamilton Harbour, at the wes tern end of Lake Ontario, on private property that is likely to be develope d in the next decade. To reduce this land-use conflict and to promote the c urrent level of biodiversity of colonial nesters in the area, artificial is lands were built in the winter of 1995-1996 with different areas designated for a variety of nesting waterbirds including Caspian terns. In 1994, prio r to island construction. we tested three substrate types for tern nesting preferences so that an appropriate substrate could be placed on the Caspian tern designated portion of the new islands. We found a preference for sand over pea-gravel and crushed stone. and indirect evidence for a preference favouring the experimental substrates over the pre-existing substrate of ha rd-packed ground. Based on these results, the small area of the island desi gned for Caspian tern nesting was surfaced with sand and was subsequently c olonised successfully. The colony established and reproduced successfully o n the designated site in 1996 and grew in numbers of nesting pairs in 1997. (C) 1998 Elsevier Science Ltd. All rights reserved.