 The sexes are similar in appearance, and the juveniles can be distinguished from adults by their lack of elongated central tail feathers and the pinkish brown coloration of their mantle, chest to belly, and flanks.They nest in large colonies in cliffs, usually near river banks, where they use their bills to dig long horizontal nesting tunnels, often eight feet or more in length.Some colonies may consist of just a few nests while others accommodate hundreds of breeding birds.