Eve and Petro found a nook even higher up than the others, where a crook-necked jug of a nest did not seem to fit. When they had built their wall as high as need be, they closed it over with a little rounded dome, and at the side they left two doorways open, one facing the southwest and one facing the southeast. And some days after this was done, had you gone to the foot of their cliff and used a pair of field-glasses, you might have seen Eve's head sticking out of one door and Petro's at the other. Ah, they had, then, some good luck left them. They had had each other in their days of trouble, and now they rested from their building labors and sat happily together in their second home, each with a doorway to enjoy. And later on they had more good luck still. For there came a day when they spent no more time sitting at ease within doors, but flew hither and yon, and then, returning to the nest, clung outside with their tiny feet and stuck their heads in at the open doorway for a brief moment before they were off again. Their nest was too far up for anyone to hear or see what went on within; but there must have been some hungry little mouths yawning all day long, to keep Eve and Petro both so busy hunting the air for insects. Soon after this one of the doors was closed, sealed tight with clay. What had happened? Were the little ones inside crowding about too recklessly, so that there was danger of one falling out? Had Eve and Petro come upon an especially good mud-puddle and built a bit more just for the fun of it? It was not very many days after this that Eve and Petro and all their comrades ceased coming to the cliff where their curious nests were fastened. Their doorways knew them no more; but over the meadows from dawn till nearly dusk there flew beautiful old swallows bearing upon their foreheads the pale mark of a new moon, and with them were their young. At night they sought the marshes, where their little feet might cling to slender stems of bending reeds; and their numbers were very many. But winter would be coming, and if it still was a long way off, so were the hunting grounds of South America, where they must be flitting away the days when the northern marshes would be frozen over. So off they went, Eve and Petro and their young, looking so much like others of the swallow flock that we could not tell who they were, now that they had stopped coming to their nest with one open and one closed doorway.