Commonly seen waterfowl include, geese, loons, ducks, grebes, and swans. There are also waterbirds like yellow-legged gulls, mallards, black-winged slits, little grebes and garganeys. Most birds, except loons and grebes, are digitigrade, not plantigrade. Eleven families of birds, including loons, grebes and most waterfowl, have this moult strategy. The Hesperornithiformes were flightless, marine diving birds that swam like grebes. This even went as far as proposing monophyly for grebes, loons, and the toothed Hesperornithiformes. In the case of flamingos, they have similar lice to those of grebes. Over 1.5 million eared grebes and phalaropes use Mono Lake during their long migrations. They are absent in grebes and some ratites, and greatly reduced in size in penguins. "transitionalis" for the smaller often non-migratory, darker-colored grebes of Mexico. It often breeds further within reed beds than other grebes. One of the very oldest fossil grebes known to date actually belongs to this genus. Grebes small to medium-large freshwater diving birds.