Differentiating Tasmanian thornbill and brown thornbill

You've seen a thornbill in Tasmania? Neat! Is it a Tasmanian thornbill? Not necessarily...

The two thornbills in Tasmania are hard to differentiate. I go by these tips published by the Australian Bird Study Association (ABSA):

Colour of leading edges of primary feathers - brown/rufous on Tasmanian thornbill (left) & cream/off-white on brown thornbill (right):

Tasmanian thornbill (left) by James Bailey from observation https://www.inaturalist.org/observations/18528637
Brown thornbill (right) by paulstanchurcher from observation https://www.inaturalist.org/observations/72605592

Colour of undertail coverts - white on Tasmanian thornbills (left) and brown on brown thornbills (right) (though this may depend on age or time of year). If this isn't super clear in these photos, see link below for better comparison photos.

Tasmanian thornbill (left) by Geoff Walker from observation https://www.inaturalist.org/observations/66760594
Brown thornbill (right) by Jeff Melvaine from observation https://www.inaturalist.org/observations/71857812

Extent of forehead scalloping & breast streaking - stronger on brown thornbills (right) than Tasmanian thornbills (left):

Tasmanian thornbill (left) by Alan Melville from observation https://www.inaturalist.org/observations/18795985
Brown thornbill (right) by Anthony Katon from observation https://www.inaturalist.org/observations/72887582

Eye colour - this is illustrated as different in Morcombe's guide but isn't a reliable diagnostic feature. Eye colour could be generally darker in Tasmanian thornbills, but it is very variable in brown thornbills (and possibly age related).

Other useful comparative photos of the two species here, made by Catherine Hamilton Young: https://www.instagram.com/p/BejxatKHiXk/?igshid=1p4w6rzbpv4mz

Posted on 27 April, 2021 03:39 by tamika_lunn