Coturnix has the goods on a handful of studies on the gene Cry2 in Monarch Butterflies:
The spatial and temporal patterns of expression make Cry2 the most serious candidate for the connection between the clock and the Sun-compass orientation mechanism. Much work, both at the molecular and at higher levels of organization needs to be done to figure out the exact mechanism by which this animal, during migration, compensates for the Sun’s movement across the sky during the day, and thus does not stray off course. Cry2 appears to be a good molecular “handle” for such studies.
Do migrant songbirds possess a similar gene? That would be a very interesting example of convergence, I would think.