METHODS FOR POPULATION-CONTROL WITHIN A SILVER GULL COLONY

Silver gulls can threaten the welfare of humans and other wildlife. Cu rrent superabundant gull numbers should be managed to reduce this risk . Denying gulls access to food at artificial sites, combined with dire ct population control, may reduce silver gull numbers in the long term . Control measures implemented at gull colonies overseas were trialled . Human disturbance in the colony associated with routine visits to st udy plots led to reduced nesting density. Egg-pricking reduced nesting success; it did not induce adults to incubate for extended periods ev en though gulls were recorded sitting on nonviable (although not prick ed) eggs for up to 76 days. Removal of eggs from nests within experime ntal plots did not affect overall nesting success for these plots. Hab itat modification, by mowing of long grass at the colony site prior to the commencement of breeding, decreased both the density of nests in mowed areas and nesting success. Selective culling of breeding adults from experimental plots was effective in reducing population size imme diately and suppressed nesting by other individuals that attempted to breed later in the breeding season. The combination of habitat modific ation, culling and human disturbance reduced breeding success at colon ies.