Sharpbeak is the Land Before Time term for Ichthyornis, though it likely applies to other predatory birds. Sharpbeaks are shown to be carnivorous, but can usually only get small prey due to their small size.
The only Sharpbeak ever seen is Ichy, who is grey, black, and white. While characters in The Land Before Time often have different colors from their species, many modern seabirds have colors like this suggesting that most Sharpbeaks have this type of coloration. Ichy relied on Dil to catch him food and in turn Dil relied on his sharp eyes to find it. He lived in the Land of Mists.
Real Ichthyornis were seabirds, so they probably live near the sea and eat mainly fish in the serues. However, since only one Sharpbeak has been seen, this is unclear.
A similar term used in the series is 'Sharptooth Flyer', which is generally used for carnivorous, tooth-bearing pterosaurs.