[5][6] Juveniles and chicks are monomorphic (the sexes are visually indistinguishable), while adults are told apart by their cere colouring and their behaviour.

First recorded in 1805, budgerigars are popular pets around the world due to their small size, low cost, and ability to mimic human speech.

They are found wild throughout the drier parts of Australia, where they have survived harsh inland conditions for over five million years.

One origin could be that budgerigar may be a mispronunciation or alteration of the Gamilaraay word gidjirrigaa (Aboriginal pronunciation: [ɡ̊iɟiriɡaː])[13][14] or gijirragaa from the Yuwaalaraay.

[15] Another possible origin is that budgerigar might be a modified form of budgery or boojery (Australian English slang for "good") and gar ("cockatoo").

[17] Alternative spellings include budgerygah and betcherrygah,[18] the latter used by Indigenous people of the Liverpool Plains in New South Wales.

[7][8][9][10] Wild budgerigars average 18 cm (7 in) long,[6] weigh 30–40 grams (1.1–1.4 oz), 30 cm (12 in) in wingspan, and display a light green body colour, while their mantles display pitch-black mantle markings (blackish in fledglings and immatures) edged in clear yellow undulations.

They display small, iridescent blue-violet cheek patches and a series of three black spots across each side of their throat.

[23] This particular parrot species has been bred in many other colours and shades in captivity (e.g. blue, grey, grey-green, pieds, violet, white, yellow-blue).

Like most parrot species, budgerigar plumage fluoresces under ultraviolet light – a phenomenon possibly related to courtship and mate selection.

[27] Budgerigars have tetrachromatic colour vision, although all four classes of cone cells will not operate simultaneously unless under sunlight or a UV lamp.

[25] While ultraviolet light is essential to the good health of caged and pet birds, inadequate darkness or rest results in overstimulation.

[29] All captive budgerigars are divided into two basic series of colours; namely, white-based (blue, grey and white) and yellow-based (green, grey-green and yellow).

[5] Outside of Australia, the only long-term establishment of naturalised feral budgerigars is a large population near St. Petersburg, Florida.

[22] Increased competition for nesting sites from European starlings and house sparrows is thought to be a primary cause of the Florida population declining from the 1980s.

[2] Breeding in the wild generally takes place between June and September in northern Australia and between August and January in the south, although budgerigars are opportunistic breeders and respond to rains when grass seeds become most abundant.

[24] It was originally hypothesised that they did this as a form of "courtship practice" so they were better breeding partners for females; however, an inverse relationship exists between participation in same-sex behaviour and pairing success.

Parasites (lice, mites, worms) and pathogens (bacteria, fungi and viruses), are contagious and thus transmitted between individuals through either direct or indirect contact.

[citation needed] The hatchlings are altricial – blind, naked, unable to lift their head and totally helpless,[5][6] and their mother feeds them and keeps them warm constantly.

Some budgerigar females, however, totally forbid the male from entering the nest and thus take the full responsibility of rearing the chicks until they fledge.

[citation needed] Depending on the size of the clutch and most particularly in the case of single mothers, it may then be wise to transfer a portion of the hatchlings (or best of the fertile eggs) to another pair.

[citation needed] As the chicks develop and grow feathers, they are able to be left on their own for longer periods of time.

Lone surviving chicks are often weaned at the youngest possible age as a result of having their parents' full attention and care.

Hand feeding is not routinely done with budgerigars, due to their small size and because young parent raised birds can be readily tamed.

Breeders have worked to produce a variety of colour, pattern and feather mutations, including albino, blue, cinnamon-ino (lacewing), clearwing, crested, dark, greywing, opaline, pieds, spangled, dilute (suffused) and violet.

When a budgerigar feels threatened, it will try to perch as high as possible and to bring its feathers close against its body in order to appear thinner.

Mineral blocks (ideally enriched with iodine), cuttlebone and soft wooden pieces are suitable for this activity.

[47] Puck, a male budgerigar owned by American Camille Jordan, holds the world record for the largest vocabulary of any bird, at 1,728 words.

[51] Small bathing suits for men, commonly referred to as togs or "Speedos", are informally called "budgie smugglers" in Australia.