The most notable characteristic of bowerbirds is their extraordinarily complex courtship and mating behaviour, where males build a bower to attract mates. There are two main types of bowers. One breed of bowerbirds build so-called maypole bowers, which are constructed by placing sticks around a sapling; in some species, these bowers have a hut-like roof. The other major bowerbuilding breed builds an avenue type-bower made of two walls of vertically placed sticks. In and around the bower, the male places a variety of brightly colored objects he has collected. These objects—usually different among each species—may include hundreds of shells, leaves, flowers, feathers, stones, berries, and even discarded plastic items, coins, nails, rifle shells, or pieces of glass. The males spend hours arranging this collection. Bowers within a species share a general form but do show significant variation, and the collection of objects reflects the biases of males of each species and its ability to procure items from the habitat, often stealing them from neighboring bowers. Several studies of different species have shown that colors of decorations males use on their bowers match the preferences of females.