sentences:  The nest building ability of the male is also sexually selected; females will lay more eggs and at an earlier date with males who are better at nest construction, with the opposite being true with males that are not.After building the nest, barn swallows may nest colonially where sufficient high-quality nest sites are available, and within a colony, each pair defends a territory around the nest which, for the European subspecies, is in size.Colony size tends to be larger in North America.