Ruby Throated Hummingbirds

during my initial research into animal migration i came across hummingbirds- which i was surprised by since there incredibly small and have a very small wingspan i didnt think that they actually migrated. again they fly exceptional distances for such small birds which is why i wanted to include them in my website/ibook content.

Ruby-throats aren't well adapted to cold temperatures; they have a tough time below the mid-20s which is the reason for their migration, the colder temperature harmful to them as well as the insects that they feed on.Most Ruby-throated Hummingbirds winter between southern Mexico and northern Panama. Since hummingbirds lead solitary lives and neither live nor migrate in flocks, an individual bird may spend the winter anywhere in this range where the habitat is favorable, but probably returns to the same location each winter. 

Ruby-throats begin moving north as early as January, and by the end of February they are at the northern coast of Yucatan, gorging on insects and spiders to add a thick layer of fat in preparation for flying to the U.S. Although hummingbirds may fly over water in company of mixed flocks of other bird species, they do not "hitchhike" on other birds. Some hummingbirds land on offshore oil rigs or fishing boats to rest. 

Before departing, each bird will have nearly doubled its weight, from about 3.25 grams to over 6 grams. For a hummer that just hatched, there's no memory of past migrations, only an urge to put on a lot of weight and fly in a particular direction for a certain amount of time, then look for a good place to spend the winter. Once it learns such a route, a bird may retrace it every year as long as it lives.

http://animals.nationalgeographic.co.uk/animals/birds/ruby-throat-hummingbird/

http://www.hummingbirds.net/migration.html