Return Rates in Two Temperate Breeding Orioles (Icterus)

We monitored two migratory oriole species, Baltimore (Icterus galbula) and Orchard (I. spurius) orioles, for information on return rate and pair fate over 4 years. The return rate after migration for Baltimore and Orchard orioles was low (38 and 35%, respectively). Pairs were more likely to dissolve due to non-return of one or both members than they were to reunite or change mates. Pair members infrequently returned to the study site and previous pairs had little opportunity to reunite in the next year. Birds with non-returning mates appeared to take advantage of the first available mating opportunity instead of waiting for the return of their previous partners.