MYLAR FLAGS AS GULL DETERRENTS

Abstract

During 1996, we evaluated the effectiveness of mylar flags for deterring herring gulls (Larus argentatus) from 2 nesting colonies (roof and breakwall) and herring and ring-billed (L. deglawarensis) gulls from 2 loafing sites at a landfill. Mylar flags (15 cm x 1.0 m) attached to wire or lathe supports were positioned at 6-m intervals at nesting colonies and 3- to 12-m intervals at loafing areas. For both nesting colonies, time of nest initiation, nest density, and clutch size in 1996 when flags were present was similar to or greater than values obtained for these parameters at the same colonies in 1995 when flags were not present. The maximum number of chicks observed at the roof colony in 1996 was also similar to the maximum number of chicks observed in 1995. At the landfill, we observed fewer gulls (P < 0.05) at 1 loafing site during the 2 weeks when mylar flags (6- and 12-m spacing) were present than during the 2 weeks when flags were not present. In contrast, gull use of the second loafing area did not appear influenced by the presence of mylar flags (3- and 6-m spacing), likely because of its small size (6 x 90 m) and proximity to a frequently used pond. We conclude that mylar flags are ineffective in deterring herring gulls (and likely other gulls) from nesting colonies but can reduce herring and ring-billed gull use of loafing areas.