The robins' dusk chorus ran from about 7:15 to 8:00 this evening. This is what might be called passive territorial singing--the birds take positions in the sunlit tops of trees, no bird nearer than around 250′ from any other. They then run through their repertoire until, presumably, they get tired of hearing their own voices & head off to roost. Not all of them I heard this evening were necessarily males, as has been commonly thought. Recent research shows that females sing this way too. The moon is waxing gibbous, not quite ¾ full. It looks like it will reach its zenith tonight around 9:30, just after passing over the gap between the two biggest maple trees in the yard.