For once, a CGI-generated bird would have been a +
I don't want to look picky or to split hairs here, but given that a sizable portion of the population is now likely familiar with what the Labrador Duck looked like, the specimen they show as a potential Labrador Duck (an extinct species) in its winter plumage (or a female one) is obviously a VERY poorly disguised Mallard. Of course, that's what it turns out to be in the end, but how the guys, including a professional birdwatcher and nature guide, could be fooled by the sight of that Mallard is beyond understanding and undermines the credibility of the film all of a sudden, after brilliant beginnings. A Labrador Duck silhouette immediately gives away its identity as a seashore diving duck (the base of its bill has the typical bump of eiders and scoters), not a marsh/pond-inhabiting wading species such as the Mallard!
If bird watching was not a major element in the storyline and in the activities of the main characters, this would certainly be less irritating. But more importantly, the sudden quest for the Labrador Duck is like the Holy Graal for the main characters, making it a central element of the utmost importance. It's really sad, because the movie includes nice shots of numerous bird species of Northeastern USA. Moreover, there are numerous mentions or short discussions on various bird species, and as an ornithologist, I can certify that all information relative to birds is very accurate, and even surprisingly well researched.
That's why I was expecting to see a better impression of a Labrador Duck, something which would have been easy. Just compare with the excellent CGI-supported Tasmanian tiger (or Thylacine) seen in The Hunter, a recently extinct species known from stuffed specimens (and old cinematographic documents). That artificially created Tasmanian tiger is so good that the final confrontation between the poacher/mercenary (played by Wilhelm Dafoe) has an incredible emotional tension and sadness.
And please don't tell me it's just a MacGuffin (which the Labrador Duck is indeed), that's not the point. A non-believable MacGuffin is worse than none altogether.