In Search of Northern Red-tailed Hawks
Historically neglected or given short mention in field guides is the boreal form of Red-tailed Hawk. If classified as a subspecies, it goes by the name abieticola. It should be looked for in winter in the northeastern United States, as I did January 30, 2016 in Orange County, NY. While all forms of Red-tail are variable and may vary from the set of features attributed to it, the individual shown above and to the right combines enough markers to put confidence in the ID. These include a heavy, blotchy belly band, rufous washed underparts with breast streaking most prominent along the sides, a dark throat, and dark upperparts with almost no white mottling. Missing from this one is barring in the tail.

Above and the two pictures immediately to the right show a second individual. The broader, bold patagial mark is another clue to its identity. Variability and probable interbreeding where borealis and abieticola meet likely produces birds that make you less sure, such as the one on the far upper right. On the far lower right is just an immature Eastern Red-tail (from the same trip), but I couldn't resist this picture. It just begs for a caption.  

As fate would have it, shortly thereafter I began noticing a dark individual close to home at Flushing Meadow Park in Queens, NY. I photographed it, in varying quality, several times into March. Most encounters were in flight, as above, with only poor pictures possible of it perched. The photo to the right was taken in December. I do believe it's the same bird having returned for another winter season -- so maybe indicative of winter site fidelity in Red-tailed Hawks?