I can certainly understand the appeal of a big bag of expensive long lenses. Birds do, after all, tend to be small and far away.
I'm not about to spend $10,000 on a set of bird lenses, though. (I'm cheap, for one thing, but I'm also not quite fit enough to carry 15 kilos of glass and magnesium around all day.)
The solution? Get close. Really close. Just beyond wing-hitting range, in this case, with a 35mm f/1.8 on a DX body.
Sure, it won't always work, but you can do an awful lot with just a single, fixed lens.