Tuesday, 12 August 2014

White Heron?

by Derek Onley
Over the last few months I've been rung a fair few times by people living around Blueskin Bay and Waikouaiti to say there's a white heron in the area, often adding that this is the first time they've regularly seen one since the 1990s. Unfortunately, far from being deservedly thanked for bothering to call and report it, they are hit by a barrage of questions: where was it, what was it doing, how big was it, what colour was it's beak, it's legs? No one has yet said "It was a white heron dammit", and rung off, which is very tolerant of them. And a good thing, because once or twice the interrogation has revealed that they more likely saw a cattle egret than a white heron and in one case possibly even a little egret. So how do you tell these white herony birds apart?
First of all you have to eliminate Spoonbills. Not difficult if you see them close up: big black spoon shaped bill! A bit harder at a distance, but compared to other herons they have relatively short necks and legs and spend most of their time asleep, bill irritatingly tucked under their back feathers, or feeding by walking through shallow water, head down, waggling their bill from side to side. They fly with their neck and bill stretched out in front and legs trailing behind and have relatively shallow, faster wing beats compared with white herons. All the other herons have deep, slow rounded wing beats and fly with their necks tucked in, except when they get excited during the breeding season. Part of their display includes flying around croaking and grunting with neck outstretched.
So that leaves the white heron or cattle egret and possibly the rarer little egret. For once the names are a help. If you see a white heron feeding amongst cattle, even nipping in close around their hooves to pick up disturbed insects or squashed worms, then it will be a cattle egret. Elsewhere the best way to tell cattle egrets from white herons is by size. White herons are big and have very long, skinny necks. You are unlikely to see a white heron alongside cattle unless there is a decent water-filled ditch nearby, as was the case last year on the Waikouaiti racecourse. But if you did, it would easily reach half way up a cattle beast's flank, whereas a cattle egret would barely reach its belly. White herons would not deem to stoop to associating with cattle but stalk their prey slowly and sedately among reeds or along the edges of rivers and ponds. However, they have been known to demean themselves by grabbing silvereyes from bird tables.
During autumn and winter, when white herons and cattle egrets are in Otago, they both have yellow bills. Little egrets have black bills and, as their name implies, are about cattle egret sized but slimmer and longer necked; in shape, more like a white heron. Little egrets feed in much the same places as white herons but are less sedate, skittishly chasing after fish with their wings half-open.
The local white herons are likely to be birds from the breeding colony at Okarito, West Coast. They disperse from there throughout New Zealand over autumn and winter, often to the same place year after year. Last year however, an unprecedented number of white herons, accompanied by the odd little egret, arrived from Australia and, at one stage, there were six together at Tomahawk Lagoon in Dunedin. They left over summer – to where, who knows – but a few have since returned and maybe the local bird is one of these?
The lone cattle egret that has been around the area may well be the one that was first seen two winters ago at Seacliff. Cattle egrets also come over from Australia in the autumn. In the late '70s and '80s thousands would fly across the Tasman to New Zealand each autumn, part of a world wide colonisation that started in Africa earlier in the century. The Cherry Farm dairy herd attracted up to 70 in the early '90s. They never colonised New Zealand, however, and only a couple of flocks of that size now visit the country. Our cattle egret is either a long lived survivor from the '90s or a rather lost, more recent arrival from Australia.
Please continue to tell me of any sightings of white herons (derekonley@yahoo.com or 03 482 2831). Hopefully I'll no longer have to subject you to an interrogation. Though, come to think of it, I might have to check that you haven't seen an intermediate egret.

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