Black-billed gulls relocate after devastating floods

Friday, 14 December 2018

A large colony of black-billed gulls on the Ashley River. (Video first published November 2018)

A large colony of endangered black-billed gulls in North Canterbury thought to have had its breeding season cut short by flooding has made a comeback.

About 2500 gulls had been nesting on the Ashley/Rakahuri River – the largest number seen there for 20 years – when their site was destroyed by severe flooding on November 25.

Members of the Ashley/Rakahuri Rivercare Group had anticipated the event would bring an untimely end to the gulls' breeding as it was already late in the season.

A large colony of black-billed gulls has managed to relocate upstream following a flood in November on the Ashley/Rakahuri River, North Canterbury, signalling potential success for their breeding season.

However, group member Grant Davey confirmed the gulls had re-established themselves further upstream at the start of December with a month of breeding season still left.

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The gulls choose to nest on islands in braided rivers which are vulnerable to flooding.

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The gulls stand among the remains of their flooded nests on the Ashley/Rakahuri River in November.

* Nesting river birds under attack from ground and air predators**

'They are definitely in their new location to breed, and they should be successful. They have less chance of getting washed out where they are now.'

While it is good news for this colony, group chairman Nick Ledgard described the braided riverbird breeding season as 'poorer than average … at best'.

Disruptive river flows, including the November flood at the peak of the season, had effectively put an end to any breeding that had not reached the chick fledging/flying stage, and displaced many resident birds.

In one area he monitored, bird numbers were down by more than 50 per cent of what was expected for December.

The wrybill population had mixed success, Ledgard said. Of the eight pairs this season, it was fortunate that at least half had a chick at the flying stage when the flood swept through. The remaining pairs lost their nests to flooding or their eggs to predators.

'It has been a season of ups and downs for the birds – which reflects the typical up and down nature of a braided river.'

The last remaining banded bird, BW-BW – a favourite with the group since he was banded in 2010 at the age of 3 – dodged all nature's obstacles again this year, fathering his 9th chick to the flying stage.