Braided River Bird Monitoring – how it works

Braided rivers are a common in Alaska, Canada, New Zealand’s South Island, and the Himalayas, which all contain young, rapidly eroding mountains. They are a unique environment inhabited by equally unique birds.

They simply cannot contain a river in a straight line. In floods especially they carry sediment, and in places where the flow slows down this settles on the bottom, thus raising it. And the water flows off to the side of least resistance. This will happen constantly during floods.

The technique for gathering bird numbers on these sort of rivers is quite simple: a team of four people spread out, in radio contact with each other, walk downstream counting every bird they see in front of them. On the ground or airborne.

And at that point the simplicity vanishes! Very finely tuned river crossing skills are needed, as well as “an eye” for the line that will give the best results. Plus physical stamina.

The tools of the trade are: a radio each, walking pole to aid crossings, binoculars, sun-cream, sun hat, good boots and gaiters [to stop gravels getting in the socks], GPS each, and a pen/paper/clipboard. Plus lunch, warm clothing, a camera etc. Warm dry socks also help at the end of the day.

A view upstream of the Hunter River that feeds Lake Hawea in Otago, New Zealand
Preparation. In this case to get into the very remote Hunter Valley. In the Wanaka area two other rivers, the Matukituki and Makarora are also done, and they don’t require a helicopter drop in. There is 25 years now of history – each river being monitored every third year.

The three year cycle is sometimes hard to maintain. The work has to be done in the spring when the birds are breeding, and this is when there is a high frequency of floods, with high levels due to snow melt.
After a short but steep climb in the helicopter from Makarora town-ship, on popping over the ridge the large and rugged Mckerrow Range come into full panoramic view [actually named after a close friend’s grandfather who did lots of surveying and exploring.
Dropping the over-night gear off by a hut, before flying further up the valley to begin the survey.
On the left [note the silt in the grass!] where we only go to avoid a complex river crossing; and where we do – the gravel on the right.
One species of many that we’re looking for. The ‎nationally vulnerable banded dotterel / tūturiwhatu, is the most common small plover of New Zealand seashores, estuaries and riverbeds.

This one is feigning a broken wing to lead the surveyor/photographer away from a nest.

After breeding, they either remain at the nesting area or move relatively short distances to nearby estuaries.
Typical nesting surface, and one of the team striding it out. Being very careful to not stand on eggs!
On the wing. A black fronted tern. Not in the Hunter though, but the Tasman River near Mt Cook. The blue colouring of the very cold water is caused by rock ground up by glaciers.

There are about six species that are primarily dependent on the braided river habitat: wrybill, banded dotterel, south island pied oyster-catcher, black-fronted tern, black-billed gull, black stilt) as well as the caspian tern and the pied stilt. The villain of the piece though is the black-back gull, as they predate on the eggs of the others.

Teaming up – linking arms for mutual support. Lots of concentration is required so it’s harder to observe what maybe in the air ahead. However the most experienced person leading the crossing, which is nearly done, has in this instance time to look. River crossing is best done by not looking down, which upsets balance, and with great care – there is no Plan B if people get swept away.
When not to cross at all – just too big and not braided into smaller channels.
The job is going well!
What we don’t want to see, but if we do, weeds are recorded as Way Points on a GPS, so that DOC staff can return later to deal to them. The most often encountered on the above mentioned rivers is this area, is often broom.

We don’t encounter many lupins in the above mentioned rivers. This photo is in the nearby Ahuriri. Lupins, which the birds don’t like, offer cover to predators. Foolishly seeds were spread many decades ago by well meaning people wanting to add some colour to the grey landscape. And the seeds can remain for years until uncovered by a flood as they’re coated with a protective oil.
A sad aspect of some surveys is that we know that after a bank-to-bank spring flood hundreds of these young birds are washed away. These are a few surviving gulls after such an event in the Matukituki a few years back.
Knock off time – a classic old-time hut.
Every hut has one
Evening and time for sleep. Tomorrow morning the survey will resume tidying up the riverbed to the right.
Job over and pickup
The long and sometimes bumpy drive home beside Lake Hawea

Obviously the results of such monitoring give a good guide as to the health of the environments concerned.

However the data as regards where breeding colonies are located, can be used for the most efficient locations for a new trapping lines. There is an attrition of traps though – during floods despite them being anchored by a chain to a long steel stake hammered in, they get washed away. Often the best compromise often considered, is for them to be near a bank that exhibits a history of stability, and place them with a shorter distance apart than the 200 mt standard in the bush, so as to create a fence of sorts.