A little bird is no longer taking flight in New South Wales, with scientific officials now declaring it extinct.

The southern species of the black-throated finch has been given the status, while a different species of the bird is still seen in Queensland.

The bird weighs about 15 grams and has a large head and a short, thick, black conical bill.

It also has a black bib, black rump and white upper tail.

The New South Wales Scientific Committee said the southern sub-species used to be widespread and abundant in the Northern Tableland and Northwest Slopes regions, from the Queensland border south to the Upper Hunter Valley.

There have only been three sightings of the bird since 1990.

Hunter Bird Observers Club president Allan Richardson said its extinction status was devastating.

"It's very, very sad; many of our threatened species are declining in their ranges," he said.

"There are not very many of our threatened species that are doing very well, so it is inevitable that as things continue, we may see some of those birds not exist in some areas."

Grazing, cropping, mining and wild rabbits have been blamed for the bird's extinction in New South Wales.

The committee said loss and degradation of habitat appeared to be the major threat.

Altered fire regimes and the spread of weeds and exotic grasses had also put the bird under strain.

Mr Richardson said he was upset that the little bird had finally lost its ability to survive.

"There's been a long, long history of land management — not just mining interests, but of course it has a long agricultural period — and some of these birds that are reliant on grasses, like the black-throated finch, do find it hard to compete," he said.

The scientific committee said the bird was eligible to be listed as a species presumed extinct because it had not been recorded in its expected habitat for some time, despite several targeted surveys aimed at trying to find it.