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
Common black hawk distinctive piping "spink-speenk-speenk-spink-spink-spink". The common black hawk is protected in the far north of its range (in the USA) under the Migratory Bird Treaty Act of 1918. Common black hawk The common black hawk ("Buteogallus anthracinus") is a bird of prey in the family Accipitridae, which also includes the eagles, hawks, and Old World vultures. It formerly included the Cuban black-hawk ("Buteogallus gundlachii") as a subspecies. The mangrove black hawk, traditionally considered a distinct species, is now generally considered a subspecies, "B. a. subtilis", of the common black-hawk. The adult common black-hawk is long and weighs on average. It has