|Title||Gull orientation by magnetic cues: a hypothesis revisited|
|Publication Type||Journal Article|
|Year of Publication||1971|
|Journal||Annals of the New York Academy of Sciences|
After a quarter century of orientation research the possibility of birds using magnetic cues is being seriously reconsidered. Ring-billed gull chicks (N=680), when released in eight-foot-diameter orientation-cages, indicate preferences for directions that will be followed during their first fall migration. The population's winter range and migration corridor were determined through banding and wing-marking projects. Statistically significant (p<.05) SE headings (mean angles) were selected by chicks tested under clear and overcast skies, in the presence or absence of natural landmarks and during stable or near stable conditions in the Earth's magnetic field. But when "magnetic storm" intensity increased to moderately severe (40 gamma and above) the birds' abilities to select SE apparently waned and random scatter resulted. These data, coupled with results from studies involving artificial magnetic fields and inquiries into the ability of birds to perceive magnetic stimuli of the intensities represented by the Earth's magnetic field, justify reevaluation of the hypotheses pertaining to this subject.