The courtyard-style houses are great for barn swallows, but they’re not so great for biologists trying to catch barn swallows. This is because about half of them are private residences, belonging to people who go to sleep at night and lock their doors when they do so. If we want to catch the barn swallows (which we do at night because their eyesight is too good to be caught in nets during the day), we have to 1) get permission to catch the birds from the homeowner during the day, and 2) arrive after the birds go to sleep (once its dark) but before the people go to sleep (9 or 10pm). This usually gave us about an hour in the evening to catch as many birds as we could.
Despite the difficulties, these courtyard houses were our best bet for catching birds in Jiuquan, and so we set off on the laborious task of knocking on every door, asking if there was an active nest inside, and asking permission to come back at night and catch the birds. We returned about an hour before dark to check that birds were roosting in the nests (sometimes they roost elsewhere, just to mess with us), and, once it was dark and the birds were sleeping, managed to scoop up 13 individuals. A pretty good haul for 1 hour of door-to-door netting!