Poor little windswept Blue Tit

And it wasn't just the Blue Tit that was windswept.
  The weather was atrocious.Wet,dank and grey.
 This shot was taken in DX mode on my D800 = 15.36 mp.And then cropped in L/R TO 1812x1208 =2mp.And I still have a workable photograph? 
 The wonders of technology? And all with a 150-500 mm lens,hand held @ 1/200 sec @ f7.1? HOW?
 And forget the 100 ISO! I had to underexpose about 4 stops or more.