Dunnock relatively lower success for females. In times of scarcity, female territories expand to accommodate the lack of resources, causing males to have a more difficult time monopolizing females. Hence, females gain a reproductive advantage over males in this case. The dunnock possesses variable mating systems. Females are often polyandrous, breeding with two or more males at once, which is quite rare among birds. This multiple mating system leads to the development of sperm competition amongst the male suitors. DNA fingerprinting has shown that chicks within a brood often have different fathers, depending on the success of the males at monopolising
Bird nest called caliology. Bird nests are also built by humans to help in the conservation of certain birds (such as swallows). Swallow nests are generally built with plaster, wood, terracotta or stucco. Artificial nests, such as nest boxes, are an important conservation tool for many species, however nest box programmes rarely compare their effectiveness with individuals not using nest boxes. Red-footed falcons using nest boxes in heavily managed landscapes produced fewer fledglings than those nesting in natural nests, but also than pairs nesting in nest boxes in more natural habitats. Bird nest A bird nest is the spot in which a