Gouldian Finches have been spotted on the fringes of Katherine township, something birdwatcher Marc Gardner says has not happened since the 1950s.

Mr Gardner said the colourful birds made an appearance at the Katherine Showgrounds on December 4, a site nationally-renowned for being "finchy".

"They were heard calling in the eucalypts at the front and came down for a drink in the late afternoon," he said.

"This site has been known to bird watchers for several years for being 'finchy' with other rare species including the Yellow-rumped Mannikin being recorded as breeding here each year.

"It is really important that the council does not mow or slash this area during the wet season as it is actually a really good habitat for many birds."

Mr Gardner, who helps convene the annual Katherine Bird Festival, said he saw and photographed a pair of juveniles that were moulting into their adult plumage ahead of breeding season.

The Gouldian Finch is currently listed as endangered under the Environment Protection and Biodiversity Conservation Act 1999.

The species was also previously listed as endangered on the International Union for Conservation of Nature Red List of Threatened Species, however in 2021 the organisation listed the birds as 'least concern'.

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Mr Gardner said he had noticed increased numbers of the rare birds in his travels across the Northern Territory, which indicated conservation efforts were working.

"There are other records around Katherine East," he said.

"Over the last several years they have been coming back into Darwin as well with the well publicised sightings around Lee Point, it's great to see them venturing back into Katherine township again.

"I'm also fortunate to see them with my work forays with new sightings around Carpentaria Highway, Daly Waters, Central Arnhem Road, Ngukurr and Numbulwar."

Other sites identified as finch hotspots by Mr Gardner included Edith Falls, Ferguson Crossing, Chainman Creek and Katherine Gorge.