Drying river rewards birds

As the birds which breed on the Ashley-Rakahuri river come to the end of their breeding season, stretches of the river are often in the process of drying up.  That means their food, small fish and aquatic invertebrates, are vanishing into ever-shrinking pools, where they are easily captured by the birds.  “Numbers of hovering terns and gulls, plus busy dotterels, stilts and oystercatchers can currently be seen at these water remnants,” says Ashley-Rakahuri Rivercare Group member, Grant Davey.  “When I was down there last week, good numbers of shags and white-faced herons were also present – and even a few of the much rarer spoonbills.”

[image above: Three black-fronted terns hovering over a riverbed remnant pool where small fish and aquatic invertebrates are being concentrated. (Photo – Grant Davey)

A spoonbill joins a pied stilt and a couple of juvenile terns around a remnant pool in the drying Ashley-Rakahuri river (Photo – Grant Davey)
A spoonbill joins a pied stilt and a couple of juvenile terns around a remnant pool in the drying Ashley-Rakahuri river (Photo – Grant Davey)

“This drying of the lower reaches of the river is not unusual,” says Ashley- Rakahuri Rivercare Group chairman, Nick Ledgard.  “The timing varies from year to year, and with declining rainfalls in the upper catchment, could well be happening more often – but it is not a new phenomenon, which some people claim.”

Once the water disappears, so do the birds, with most of them heading for the estuary and the coast and often further north for the coldest winter months. Wrybill fly up to feeding grounds in the northern N. Island, particularly the mudflats of the Manukau harbour and the Firth of Thames.  They are not expected back until the spring, when they are first seen down around the estuary before flying up the riverbed to their traditional breeding sites.

Fresh-water flounder are not often seen far up the Ashley-Rakahuri river.  This one was in a drying up riverbed pool some 8 km away from the coast.  (Photo – Nick Ledgard)
Fresh-water flounder are not often seen far up the Ashley-Rakahuri river. This one was in a drying up riverbed pool some 8 km away from the coast. (Photo – Nick Ledgard)