A MODULAR TUNNEL-AND-BLIND SYSTEM TO REDUCE INVESTIGATOR DISTURBANCE OF BREEDING COLONIAL WATERBIRDS

We constructed an 80-m-long above-ground tunnel to reach 8 blinds in a colony of Double-crested Cormorants (Phalacrocorax auritus) and Ameri can White Pelicans (Pelecanus erythrorhynchos), and secured specimens by use of a light-weight telescopic rod with attachments. We visited t he tunnel-and-blind system every third day during the breeding seasons of 1994-96 and collected 16 cormorant and 8 pelican eggs, 67 pelican and 61 cormorant carcasses, and 77 live cormorants without leaving the system. Nest abandonment due to investigator disturbance was concentr ated in an area within about 20 m of the tunnel entrance. We believe t he above System could be useful in other studies of ground-nesting col onial waterbirds, especially those requiring repeated access to a larg e number of nests and collection of specimens.