Very possible with NEX, although I wouldn't count on getting much in focus if the birds are in flight. Overall, most nikon Ai-S lenses perform well. This is 300mm F4.5 Ai-S, @30 year old lens which can be found on eBay quite reasonably. Hint: try and find one with the JCII sticker! All shots handheld, between f5.6-f8 great egret gbh gbh gbh white morph, (mating pair), harsh backlighting, a testament to NEX sensor latitude black crowned night heron, ISO 800, 1/250, borderline handholding sharpness purple galinule Higher resolution available via flickr... Thanks for this site!