The Passeriformes contains 5,000 or so species[1][2] found all over the world, in which the vocal organ typically is developed in such a way as to produce a diverse and elaborate bird song.
[2] The Tyranni have a simpler syrinx musculature, and while their vocalizations are often just as complex and striking as those of songbirds, they are altogether more mechanical sounding.
[4] The distribution of their basal lineages suggest that their origin and initial diversification occurred exclusively in the Australian continent and only about 40 million years ago, oscines started to colonize Eurasia, Africa, and eventually the Americas.
[5][4][6] The song in this clade is essentially territorial, because it communicates the identity and whereabouts of an individual to other birds, and also signals sexual intentions.
This organ, also known as a song box, can be found where the windpipe meets diverging bronchial tubes which lead to the lungs.
Mate choice in female songbirds is a significant realm of study as song abilities are continuously evolving.
[13] Another theory known as the "song-sharing hypothesis" suggests that females prefer simpler, more homogenous songs that signal a male of familiar territory.
As birdsong can be broken into regional dialects through this process of mimicry, the foreign song of a newcomer suggests the lack of territorial possession.
This can be costly in the wake of territorial conflicts between disparate songbird populations and may compel a female to prefer a male spouting a familiar song of the area.
[14] Sibley and Alquist divided songbirds into two "parvorders", Corvida and Passerida (standard taxonomic practice would rank these as infraorders), distributed in Australo-Papua and Eurasia respectively.
The remaining 15 oscine families (343 species in 2015[1]) form a series of basally branching sister groups to the Corvoid - Passerid clade.
Australian endemics are also prominent among basal lineages in both Corvoids and Passerids, suggesting that songbirds originated and diverged in Australia.
The rufous scrubbird, Atrichornis rufescens, is essentially confined to the Gondwana Rainforests of Australia World Heritage Area, occurring in both Queensland and New South Wales sections.