There's been an explosion in fantail numbers since last year's pest removal operation.

Tuis, tomtits and fantails are just some of the native birds flourishing in the Brook Waimarama Sanctuary, a recent report shows.

The flutter of feathers and the songs of New Zealand birds can be heard inside the sanctuary fence and a monitoring programme has shown the sounds are only going to grow.

A bird counting project began in 2010.

Brook Sanctuary Waimarama general manager Hudson Dodd said a nationwide standardised bird counting method was used called the five minute bird count.

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Four times a year, a trained individual with good knowledge of the sound and sight of native birds enters the sanctuary and visits 20 sites.

Five minutes is spent at each site where data is recorded of all the birds seen and heard.

"Last month, the first of those quarterly bird counts was done following the first breeding season and following the pest removal operation last year.

Peter Rees Photography It's hoped that once the sanctuary becomes more fully populated by different species, birds like the tui will spread out into people's gardens.

"This is the very first result to see what the effects of the pest removal has been."

Dodd said the results were "very encouraging".

The silvereye and tomtit population grew "quite significantly".

"For tui and fantails, the results are downright dramatic – major increases."

The outcome was more moderate for other native species, he said.

"It's still early days, but basically what this trend is showing is that over time people will indeed experience significant bird life when they visit the sanctuary.

"We also expect in time once the sanctuary becomes more fully populated by the different species ... the birds will spill out beyond the sanctuary fence and into people's gardens."

SUPPLIED/FAIRFAX NZ The tomtit population has grown significantly.

Dodd said the results were testament to the choice in location for the sanctuary.

"It was always recognised by DOC and conservationists as an excellent site for a project like this because the vast majority of the sanctuary is pristine forest."

Once results showed a steady rise in current numbers, he said other native birds could be introduced to the sanctuary including kiwi, kaka and kakariki.

The sanctuary has been closed to the public since the poison drop began in July last year.

Dodd said there were plans to reopen this winter on a donation basis.