AN INVESTIGATION OF HOMING ABILITY IN TWO SPECIES OF GULLS.

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Abstract
Summary.: In the most extensive, compact series of homing experiments to date, 249 Lesser Black‐backed Gulls (a migratory species) and 91 Herring Gulls (a restricted nomad) were used, together with 20 other seabirds. Lesser Black‐backed Gulls on release showed a significant homeward orientation which was absent when the sun was obscured by clouds. Some direct evidence and an analysis of the homing success indicated that a large proportion of the gulls were homing by an inefficient method, probably random exploration for known visual landmarks. A minority were, however, homing by a method not dependent on the distance or area of release. Some form of sun navigation is suggested by the orientation behaviour. The species were not suitable for detailed investigation of individual variation in navigational ability. The poorer overall performance of the Herring Gulls could be explained by then being a much smaller proportion of able navigators among them. Masking the earth's magnetic field by airborne magnets did not affect homing ability.