Feasibility of administering an oral reproductive inhibitor to resident Canada geese

We evaluated our ability to deliver adequate daily doses of the reproductive inhibitor, nicarbazin, to individually marked resident Canada geese (Branta canadensis). We also evaluated the efficiency of nicarbazin in reducing egg hatchability. The study was conducted prior to and during the egg-laying period at a wildlife sanctuary that has a large, problem-causing population of resident geese that were accustomed to being fed by people. Twenty-eight adult females were marked with individually identifiable neck collars, 24 of which were affixed with radio transmitters. Grit pellets and gelatin capsules containing nicarbazin were fed to these geese from March 17, 2001 through April 26, 2001. We attempted to deliver doses to geese each day. Doses varied among geese throughout the study and within geese daily because all geese were not present at the site each day, and even if present they accepted the bait to varying degrees. Seven of our target birds did receive what we believed to be adequate doses of nicarbazin. We documented that only about 11% of the resident population nested at the sanctuary, while the others nested in remote areas. We were able to locate 5 nests of birds that received adequate doses, but found no significant effect of nicarbazin on the hatchability of their eggs compared to untreated geese. We found that the biggest challenges to orally-fed reproductive inhibitors include the palatability of bait relative to other food sources, reduced feeding during the breeding period, and movements and territoriality associated with nesting