Birdwatching: plumage, migration and calls

On a duck, the patch of glossy colour on the rear edge of the wing is der Spiegel, or in full der Flügelspiegel: the mirror. English ornithology says the same thing in Latin, since speculum is simply the Latin for a mirror, but a German reader hears the everyday word, and meets it again in places no field guide mentions. A hunter’s Spiegel is the pale patch on a deer’s rump that shows as the animal bounds away. On a lab report, der Blutzuckerspiegel is a blood sugar level, and der Meeresspiegel is sea level: the flat surface of a liquid, read like a mirror. What joins them is a surface that catches the eye, and the compound usually says which one is meant. In this list it is the duck’s, and it earns its place, because the speculum stays visible after the rest of the drake has moulted into a drab Schlichtkleid.