'A little inward note of complacency'

 The swifts have been livelier than ever today, perhaps encouraged by the hot sun. Flying low, they've been hurtling past their nest sites, screaming as they go, then ascending to perform their aerobatics with equal gusto over the rooftops. Gilbert White was fascinated by these 'amusive birds', which he observed with delight. Here he describes their behaviour at the height of the season: 
'In hot mornings several, getting together in little parties, dash round the steeples and churches, squeaking as they go in a very clamorous manner; these, by nice observers, are supposed to be males serenading their sitting hens; and not without reason, since they seldom squeak till they come close to the walls or eaves, and since those within utter at the same time a little inward note of complacency. When the hen has sat hard all day, she rushes forth just as it is almost dark, and stretches and relieves her weary limbs, and snatches a scanty meal for a few minutes, and then returns to her duty of incubation.'