Down by the River

It’s murder down by the river.  There are three species of endemic bird that only breed on the braided riverbeds of NZ.  Pre-european they could be found on the riverbeds from Hawke’s Bay to Bluff but they are becoming increasingly restricted to Canterbury and Otago.  They’re being hit on four fronts, loss of habitat (weeds, agricultural encroachment and river engineering), altered riverflows (dams and irrigation out-takes), introduced mammalian predators and an imbalance with natural predators having boomed in a flow on from pastoralism.  A fifth factor, climate change, is potentially causing earlier snow melt with big floods that take out all but the earliest nests.  If chicks are big enough they can survive big floods.

Kahu, Harrier hawks are one natural predator but the worst, mainly because they share the breeding habitat and are in plague proportions, are black-backed gulls.

Southern black-backed gulls (SBBG) are a native bird, but where at European settlement they were solitary nesters mostly in the mountains, now with the Canterbury Plains being one giant milk factory they have boomed.  Having walked it, I know the Rangitata below Highway One is  one giant gull colony for most of the roughly 20km out to the coast.  In the gallery below click on an image to enlarge it.  Riverbed photos are taken through one side of binoculars plus the cameras zoom, in these photos the only things that should be there are the rocks and gravel.

SBBG are voracious

But then there’s the feral cats too, and they will cross water.

Hedgehogs are another major problem for ground nesting birds, skinks and large invertebrates like weta.

This link goes to a very good rnz article on the problem as well as the video below and a 31minute podcast that outlines the problem, includes the audio for the video below, and at 17 minutes talks about a trial in using scent to discourage predators from hunting our special riverbed nesters.

If you only watch one of these videos, this is the one. Warning: contains carnage.

This entry was posted in Canterbury, Ecology, NZ Birds, Uncategorized and tagged , , . Bookmark the permalink.

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