Swifts aren’t quite what they seem

Bird Watching (UK) - - Meet The Family -

Swifts are the UK’S archety­pal sum­mer birds, ar­riv­ing as late as mid-may and gone again in early Au­gust. Their scream­ing flights through city streets and above sub­ur­ban gar­dens are cer­tainly a memorable part of the warmer months. It’s hard not to feel slightly short-changed, though, when you re­alise who the clos­est rel­a­tives of their or­der (Apo­di­dae) are. As well as the treeswifts (Hemiproc­nidae) of south­ern and eastern Asia, they are joined in the or­der Apod­i­formes by the hum­ming­birds, of the New World. The two lines of the fam­ily (in­sect-eat­ing swifts and treeswifts, and nec­tar­guz­zling hum­ming­birds) di­verged as long as 42 mil­lion years ago, with the hum­ming­birds then fur­ther di­ver­si­fy­ing into 338 species in re­sponse to the myr­iad habi­tats of the Amer­i­cas, and the many dif­fer­ent plant species therein. There is an Old World fam­ily of birds that, at first sight, might seem to be closely re­lated to hum­ming­birds – the sun­birds of Africa and Asia (although they gen­er­ally perch to feed, rather than hover). In fact, though, this is an ex­am­ple of con­ver­gent evo­lu­tion, in which fam­i­lies of only dis­tantly re­lated birds evolve many of the same char­ac­ter­is­tics in or­der to fill the same eco­log­i­cal niche. An­other fam­ily, the hon­eyeaters of Aus­tralia, have sim­i­larly evolved sep­a­rately but along sim­i­lar lines.

CON­VER­GENT EVO­LU­TION Blue-faced Hon­eyeaters fill a sim­i­lar niche to sun­birds and hum­ming­birds DI­VERSE DEVEL­OP­MENT A Marvelous Spat­ule­tail – there are more than 300 dif­fer­ent hum­ming­bird species UNIQUE Sword-billed Hum­ming­birds have evolved amaz­ing bills to al­low them to feed deep in­side flow­ers

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