Loons are similar on the water, but lack hooked bills. Most loons hold their bills level while swimming while cormorants hold theirs angled upwards. Anhinga has a long, pointed bill and a much longer tail. All adult cormorant species in the U.S. are separable by the shape and color of the gular areas. No other species has a dull yellow gular region bordered by a thin white line. Double-crested Cormorants are quite similar to Olivaceous Cormorants, especially the immatures. In breeding plumage, the adult Olivaceous Cormorant has a distinctive white border to the gular region. At other times of year, note that the smaller Olivaceous has a duller, pointed gular region, a longer tail, and a slimmer build.