Thirteen percent of the world's pohowera/banded dotterels make their homes along three Hawke's Bay rivers. Photo: NZ Bird Atlas
Dotterel populations have experienced a record decline along Hawke's Bay rivers and coastline, prompting concern from the regional council.
The decline is being blamed on the effects of Cyclone Gabrielle, which devastated the region in February last 2023.
A Hawke's Bay Regional Council report surveyed hundreds of kilometres of coastline and riverbanks along the Tukituki, Ngaruroro and Tūtaekurī between 2019 and 2024.
Ecologist Nikki McArthur said there had been a significant decrease across several species when this year was compared with pre-cyclone numbers.
The worst-affected river was the Tūtaekurī, where pohowera/banded dotterel numbers fell by 51 percent. Along the Ngaruroro river there was a 20 percent drop, and along the coast it fell by 31 percent -- the steepest population decline since bird surveys began in 1962.
McArthur said that reduced the national and global population by an estimated 2.5 percent, assuming the decline was the result of deaths, rather than a change in where the birds were living.
"We may not ever know for sure, but hopefully in another three to five years' time we'll have the opportunity to repeat our surveys in Hawke's Bay," he said.
If the birds had simply relocated, he would expect the population to bounce back quickly, he said.
The three rivers supported internationally significant populations of indigenous shorebirds, including 13 percent of the global population of pohowera/banded dotterels.
A banded dotterel chick. Photo: Ailsa McGilvary-Howard and Ted Howard
This species had an estimated national population size of about 19,000. The Hawke's Bay population pre-cyclone was about 2800, and now, it was down to about 2400.
McArthur said the survey results highlighted how catastrophic the cyclone had been for river and coastal habitats, for species already classed as at-risk or threatened.
A team of 10 had surveyed the coastline and riverbanks on foot, which took two to three weeks, McArthur said, covering about 60 kilometres a day.
"We were observing large stretches of river with very deep deposits of fresh silt and sediment, burying the substrates that these birds breed on and probably drastically disrupting their food supply as well."
There were also large quantities of woody debris, and severe erosion of the banks and foreshore.
In future, McArthur said, work needed to be done to protect and enhance these habitats through predator control, keeping humans and cars away from nesting sites, and keeping dogs on leads and cats inside at night during the nesting season.
The best defence was to get the numbers back up so the population was resilient to disasters, he said.
Decline by the numbers
- Pohowera/banded dotterel numbers dropped 15 percent across the three rivers - with the worst cases being 51 percent on the Tūtaekurī River and 20 percent on the Ngaruroro - and by 31 percent along the coast
- Black-fronted dotterels down 30 percent across the three rivers
- Tūturiwhatu/New Zealand dotterels down 36 percent along the coast