Lesser Scaups are fairly common wintering in Southwest Florida, but we almost never find Greater Scaups here. Identification can be very difficult between the two species. However if you have an opportunity to bird in north Florida, you may have to try. The '10,000Bird' blog has an excellent page on comparing these birds. Try this hyperlink to their site - http://10000birds.com/lesser-scaups.htm/ - to learn more.