So What's With The Robins This Winter, Anyway?

I just looked out the window to see a group of songbirds plucking crabapples off a tree outside.  There was a pair of cardinals, a couple of those spotty female starlings, a waxwing or so, and -- much to my surprise -- not one, but 8 robins.  It's mid-December, and robins are normally very hard to find in Michigan this time of year.  And you hardly ever see them travelling in packs, no matter what time of year it is. 

When I looked more closely, it got weirder.  All the other birds looked completely typical of their species, but fully half the robins were what I've thought of for some time as "pastel."  Instead of being dark brown along the top and back and brick-red in front, these have pale silvery-brown heads and wings, and their fronts are watercolor tangerine.  I've learned to call these "leucistic" robins because that's the birdwatching term for them.  And one robin, that looked pretty average at first glance except for a dusting of snow, proved on closer inspection to have white spots, like a reverse Dalmatian.

So all I'm saying is that there's something up with the robins this winter.