July 2010, canon announced their 50,000,000th lens. (since EF in the 80s)
This week, Nikon announced they'd made their 65,000,000th lens. (since 1959)
Seeing as how a lot of the early Nikons can't be used on the modern bodies (and you need a chart to figure out which ones), they're probably about equal in terms of how many lenses are out there that can mount to each system (and canon has the advantage of being able to mount nikon lenses, but not vice-versa).
The lack of a 200-400 is also something that first came to my mind, but in primes they're probably equal, they both have 300/2.8, 400/2.8, 500/4, 600/4 (do nikon have an 800mm?), and canon had the 1200mm.
Canon tried to make the 400/4 DO a birding lens, seeing as it's smaller and lighter because of the DO element, but I don't think it really took off from IQ issues.
Bodies aside, I think 3rd-party lenses are the go for birding, sigma has the 150/170-500, the grenade-launcher 200-500/2.8, and the uber-long 300-800mm (although I don't know how well the IQ is on any of these)