Watching Birds

The twenty-fourth entry is o dormitório das aves, the place a flock comes back to at dusk, and the Portuguese is completely transparent: dormir is to sleep, and o dormitório is the room where sleeping is done, whether the sleepers are schoolchildren or starlings. English will not lend « dormitory » to birds. It keeps a separate noun, « roost », and that noun has an odd life. Very few speakers use it of an actual reedbed; most meet it only inside two fixed sayings, and both have left the birds behind. To « rule the roost » is to be the one who decides in a household or an office, taken from the bird that claims the best perch and keeps it. And « chickens come home to roost » is said when somebody’s old decisions arrive to be paid for: the consequences fly back at evening to the place they started from, exactly as the flock does. So the literal word is worth learning first and the two sayings straight after, because in ordinary English the sayings are far commoner than the thing.