Winter and spring 2013 have been cooler than spring 2012, when spring was extra early and very warm across much of the map. Think about that as you compare maps showing where robins are singing today with this time a year ago:
Robin Singing 2012
Robin Singing 2013
do you notice about the latitude of the song sightings for this week (bright yellow dots)
compared with those for the same week (the aqua-blue dots) on the 2012 map?
Robins sing when they are back on their summer nesting territory. How would you explain why robins are not singing as far north this spring than they were in 2012 at this time?