About Melopsittacus undulatus (Shaw, 1805)
Melopsittacus undulatus, the wild budgerigar, averages 18 cm (7 in) long, weighs 30–40 grams (1.1–1.4 oz), and has a 30 cm (12 in) wingspan. Wild individuals have a light green body, with pitch-black mantle markings (blackish in fledglings and immatures) edged in clear yellow undulations. Adult budgerigars have yellow foreheads and faces. Before developing adult plumage, young birds have blackish stripes that extend down to the cere, until they reach around 3–4 months of age. All individuals have small, iridescent blue-violet cheek patches, plus a series of three black spots on each side of the throat; the two outermost throat spots sit at the base of each cheek patch. The tail is cobalt, with central yellow flashes on the outer tail feathers. Their wings have greenish-black flight feathers and black coverts with yellow fringes, plus central yellow flashes that are only visible when the bird is in flight or has its wings outstretched. Budgerigars have olive grey bills, blueish-grey legs, and zygodactyl toes. Wild budgerigars in their natural Australian habitat are noticeably smaller than captive-bred individuals. This parrot species has been selectively bred in captivity to produce many other colors and shades, including blue, grey, grey-green, pieds, violet, white, and yellow-blue. Budgerigars sold in pet stores are most commonly blue, green, or yellow. Like most parrot species, budgerigar plumage fluoresces under ultraviolet light, a phenomenon that may be linked to courtship and mate selection. The color of the cere, the area that contains the nostrils, differs between sexes: it is lavender or baby blue in mature males, pale brownish or white (when not breeding) turning brown (when breeding) in mature females, and pink in immature birds of both sexes (young males usually have a more even purplish-pink cere color). Some female budgerigars only develop a brown cere during breeding season, which later returns to their normal non-breeding color. Young females can often be identified by a subtle, chalky whiteness that begins around the nostrils. Males of certain color morphs – albino, lutino, dark-eyed clear, or recessive pied (also called Danish pied or harlequin) – retain the immature purplish-pink cere color for their entire lives. Mature males usually have a light to dark blue cere, but some color mutations result in periwinkle, lavender, purplish, or pink ceres. This includes dark-eyed clears, Danish recessive pieds, and inos, which also usually have much rounder heads. Female budgerigars are more behaviorally dominant than males of the species, and may act aggressively toward males. Budgerigars have tetrachromatic color vision, though all four classes of their cone cells do not operate simultaneously unless the bird is under sunlight or a UV lamp. The ultraviolet spectrum makes their feathers appear brighter to other budgerigars, to help attract mates. The throat spots of budgerigars reflect UV light, and this can be used to distinguish individual birds. Ultraviolet light is essential for the good health of caged and pet budgerigars, but inadequate darkness or rest leads to overstimulation. Budgerigars are nomadic birds, and flocks leave a site when local environmental conditions change. They live in open habitats, primarily the scrublands, open woodlands, and grasslands of Australia. They normally form small flocks, but can gather into very large flocks when conditions are favorable. The nomadic movement of their flocks is tied to the availability of food and water. Budgerigars are capable of switching between two distinct flight speeds depending on the situation. They will sometimes swarm in groups of thousands of individuals. Drought can push flocks into more wooded habitats or coastal areas. They feed primarily on grass seeds, and also eat the seeds of spinifex, and sometimes ripening wheat. They also opportunistically feed on growing cereal crops and lawn grass seeds. Because the seeds they eat have low water content, budgerigars rely on access to fresh surface water. Outside of Australia, a naturalized feral population of budgerigars lived near St. Petersburg, Florida for over 50 years. Increased competition for nesting sites from European starlings and house sparrows is thought to be the main cause of this population’s decline starting in the 1980s, and the entire Florida population went extinct in 2014.
