The exterior is constructed of grass, twigs, feathers, weeds and other light detritus, while it is lined with feathers and down – which may come from cactus wrens or other species.[23][5] Nests built in urban settings use a much wider variety of materials, including many human made items such as paper, string, lint, and notably: chicken feathers, used as nest lining in great quantities where available.[10]:24 Urban materials, while easily available, make for weaker and less sturdy nests.[10]:28 A tubelike entrance, about 15 cm (6 in) long, leads to the main nest cavity.[14] The entrance is often oriented to take advantage of the cooling effects of prevailing winds.[25] Nest building takes between one and six days, with Anderson and Anderson reporting an average time of 2.7 days.[10]:26 The nesting pair usually focuses on nest building only for the first three hours of each morning.[7]