Skimmers use the longer lower mandible of their bill to "skim" the surface of the water for food while in flight [December; Florida]
![Skimmers use the longer lower mandible of their bill to "skim" the surface of the water for food while in flight [December; Florida]](https://photos.smugmug.com/BIRDS/Gulls-Terns/Black-Skimmer/i-vJzfSPZ/0/e42550d2/S/Black%20Skimmer%20FL%20IMG_0579-S.jpg)