157627 Black-throated Diver Gavia arctica L 60-70cm. Swims buoyantly with bill held level. Dives frequently. Sexes are similar. Adult in summer has blue-grey nape and head, and black throat; sides of neck have black and white lines. Back is dark with white spots; underparts are white. In winter, upperparts mainly grey-black and underparts whitish; note white patch on flanks at water level in swimming birds. Juvenile is similar to winter adult but grubby-looking. Voice Mostly silent. Status Rare breeding species on large Scottish lochs. Scarce in winter, mainly in coastal waters.