Migratory movements in the autumn are generally between late August to mid-October, peaking at the end of September and beginning of October in the east, but sometimes migration extend into November. Meanwhile, spring northward migration may be any time from the end of February to May, with the last ones leaving Mexico in April and very late individuals were passing over south Texas in late May. Generally, spring migration is more dispersed and less consistent than fall migration. There is evidence from the Great Lakes region that spring migration is occurring sooner due to warming temperatures in recent years. Passage appears to be timed to coincide with that of their main prey, medium-sized birds. In migration, first-year juveniles precede two-year-old hawks which themselves precede adults when moving south in fall. Furthermore, females of all ages tend to migrate sooner and spend longer in winter quarters than like-age males, the latter staying relatively north and traveling back again earlier. Interestingly, the sharp-shinned hawk (despite the even more dimorphic migration times between sexes) showed no strong difference in distance on migration between the sexes, unlike female Cooper's which sometimes can move considerably further than males. At regular western migration sites, the average difference of passage timing for Cooper's hawks of the earlier females and later males of like-age was five days. In the Marin Headlands, migration of the sexes differed by 6 days in juvenile, first-year females and males and by 11 days in older females and males. Like other "Accipiters" (but unlike falcons), Cooper's appear to not start moving until day is warmer and thermals can be used. During migration they favor mountain ridges and coastlines, which coincide with migratory raptors routes in general. This species can seem to cross some bodies of water unlike most sharp-shinned hawks but seldom do so over wide bodies of water. However, they have been seen to turn up in such oceanic vicinities as the Florida Keys and Cuba, and so are capable of crossing larger than usual bodies of water. It is thought that Cooper's hawks also avoid the Great Plains while migrating as well. Like many other raptors, Cooper's hawks favor strong northwesterly winds during autumn passage.