Nikon just made some birders very happy. This is a great travel lens for birders who like to go to exotic locales where they fly in on a puddle-jumper prop plane. Shorter, lighter, can stuff it under the seat or in the overhead (if any) of the smallest planes.
The Canon 400 f/4 DO (Canon's name for Fresnel-type lens use) with 1.4 x and 2.0 x v. III teleconverters have been a big hit among birders shooting Canon.