Homing in Leach's storm petrel Oceanodroma leucorhoa leucorhoa

Spencer, Christopher John (1979) Homing in Leach's storm petrel Oceanodroma leucorhoa leucorhoa. Masters thesis, Memorial University of Newfoundland.

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Abstract

During the summers of 1975 and 1976 homing behaviour was studied in Leach’s Storm Petrel, Oceanodroma leucorhoa leucorhoa. Five displacements involving 148 different birds were performed. Homing times and success were highly variable even amongst control home island releases. Distance and direction of displacement had no marked effect on medium range releases. However, near the breeding island, downwind birds performed better than upwind birds, presumably as a function of olfactory cues emanating from the island. Birds displaced inland did not perform as well as those released an equal distance away but at water’s edge. Incubation shift length, sex, breeding experience, or previous displacement experience did not appear to affect homing times. Weight was important : heavy birds homed sooner losing weight en route while light birds took more time while gaining weight. Both physical size and motivational factors are implicated in this phenomenon. -- In orientation activity chambers, adults at four release sites did not orient homewards. However some of these adults, as well as adults tested on the home island, faced downwind. In contract, chicks were less active and randomly oriented. -- A food sampling study indicated that Leach’s Storm Petrel may obtain many of their prey items within the environs of the breeding colony though to procure one major group, myctophid fishes, a one way trip of at least 125 km to the SW would be necessary. Another prey species, Hyperia galba, is specific to inshore waters. These two food types could provide positional information to a petrel. -- While netting birds, record was kept of the number of birds that struck the net. The number of collisions was nonsignificantly negatively correlated with wind speed, illumination level, and the number of times the net had been at one spot. However, all but one of the interactions were significant suggesting the variables had real though weak effects. -- Taken together the results were interpreted as being consistent with the homing literature in indicating a limited redundancy of orientation systems and a situation dependent hierarchy of cues. Compass usage was not demonstrated with Leach’s Storm Petrel but suggestions for further work were made.

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