Imagine a male bird migrating back north after a long, tough winter in Central America, Assume it flies during the day

In this example the male migrates north following the end of winter during the day to the same nesting grounds and partner as the previous year. The question asks for two advantages to the male for this behavior. The first advantage is wintering in a milder and gentler climate saves energy and increase the male's survival rate. The second benefit is that in moving to wintering grounds they have a fresh supply of food to consume before the return to the mating grounds.

For some basic info on migration see: http://en.wikipedia.org/wiki/Bird_migration

1.b. The costs that must be weighed against the benefits of migration includes the increased energetic requirements of migration and the potential for territorial competition upon returning to the breeding grounds. With each new season the parental males will face competition from their male offsprings for the breeding grounds and competition from males who have lost their territories.

1.c. In order to use the sun to navigate during migration these birds must be able to detect polarized light changes as they travel in order to readjust their magnetic compass. Their internal clock or circadian rhythm is also critical in using the sun as a compass. As the local time diverges from the bird's internal clock it is their cue to migrate.

See http://www.sciencemag.org/cgi/content/full/291/5502/300, http://www.physorg.com/news74439346.html, http://www.albertaclassic.net/suncomp.php

1.d. Other migratory cues can include magnetism, visual, olfactory. Changes in magnetic fields are detected by magnetic particles in the bird's trigeminal ganglia that have altered energetic states depending on the magnetic fireld. Visual cues can be used such as landmark recognition and would be especially beneficial to daytime traveling birds that return to the same nesting site year after year. Olfactory cues can be region or area specific and can serve to map migratory paths.