Dispersal and migration of Ring-billed Gulls from a Michigan population
|Dispersal and migration of Ring-billed Gulls from a Michigan population
|Year of Publication
|Jack Pine Warbler
During orientation studies with Ring-billed Gulls from the Rogers City, Michigan population an attempt was made to determine the seasonal patterns of dispersal, migration, and inhabitation for the various age-classes from the colony. Band recoveries and trap-retrap data were used for this purpose. Juvenile ring-bills usually leave the colony by 1 August and scatter over the northern half of the state, with a small proportion reaching other Great Lakes states or eastern Canada. Southward migration apparently begins in September. Period 3 recoveries indicate a preference for the Gulf coast, especially Florida. In March and during Period 4 there was a 60% decline in Florida recoveries which suggests a spring migration of juveniles. Some of the young birds wander as far north as Michigan and Canada. Seventeen (48.6%) of the recoveries for one-year-old ring-bills were from Michigan and 51.4% were scattered over the eastern United States and Canada. The Michigan birds do not inhabit the vicinity of the breeding colony. Southward exodus occurs by, or during, November and the birds again concentrate along the Gulf Coast. Few data were available for two-year-olds and these were biased by selective collecting of specimens of this age class. Recapture results indicated that about 10% of the Rogers City population may be represented by this group.