08 December 2013

Birds of New Zealand: part two: seabirds

Juvenile kelp gull
Seabirds confuse me.

In the past, I thought all seagulls looked alike. So, I consulted an expert, Brent Stephenson, and the book he co-authored with Paul Scofield, Birds of New Zealand: A Photographic guide, for help identifying my gulls.

Turns out, there are kelp gulls, and red-billed gulls, and black-billed gulls, amongst others. And those large brownish-feathered birds, often seen with gulls, which I thought were called Mollyhawks (in fact, there’s no such thing, the name is MollyMawk), are actually just juvenile gulls (even though these kids look a whole lot bigger than their parents).

One of the most common seabirds in New Zealand is the Red-billed gull (below), which is found all along our extensive coastline. Their distinctive red bills and legs are how we can tell them apart from the black-billed gulls, which are otherwise very similar. Having said that they are our most common seabird, I should add that populations have taken a nose dive in recent years and this may be related to their diet. Their usual foods are plankton, little fishes and marine invertebrates like molluscs, anemones and crustaceans, but they are also scavengers, selecting choice morsels from rubbish dumps and quickly gulping down tasty titbits thrown at them by humans. The fact that rubbish in landfills is now buried may be a contributing factor to their dwindling numbers but over-fishing and climate change are also possibilities.

The Kelp gull is also common in much of New Zealand and, indeed, throughout the world, and it also likes to scavenge at any opportunity. During my early morning walks through Auckland’s Domain I often see these gulls collecting worms from the roads, particularly after rain has flushed out worms from the grass verges.

The Kelp gull is distinctly black and white (compared to the grey and white of the red-billed and black-billed gulls). It is larger than the red-billed gull, and has a yellowish-orange beak and legs. Its scientific name is interesting: Larus dominicanus dominicanus is, as you might guess, named for the similarity of its plumage with the habits worn by priests of the Dominican Order.

Sadly, the Black-billed gull is on the critically endangered list. This photo (right) is not one of them – rather, this serves to show how the juvenile red-billed gull can easily be mistaken for the black-billed variety, due to its blackish bill. But the real black-billed gull’s beak is sharper and the bird itself is more finely featured, with very light grey upper wings.

The Black-billed gull can be found throughout New Zealand but is most common along the South Island’s braided river systems, and can be seen following along behind farm tractors ploughing the Canterbury plains.

Little Pied Shag
Apparently, the word shag is Old English and relates to the crest on the bird’s head – think, for example, of the word shaggy. New Zealand has several distinct species of shags and you could easily be confused into thinking we have several different species of little shags as our Little pied shag can vary substantially in colour – some are mostly dark, some have two or more different colours, others are streaked. This little fellow (below) was happily fishing around Auckland’s inner city wharves.

I took this photo of a Dotterel (below) in Whangamata last Christmas, while visiting an aunt who lives there. It was at the end of the beach nearest the estuary so, fortunately, away from the bulk of that busy beach’s foot traffic. New Zealand dotterels are shorebirds, usually found on sandy beaches and sandspits or feeding in tidal estuaries. They once were common and widespread but are now highly endangered, partly due to a loss of habitat, partly due to predation by introduced mammals and partly due to their breeding grounds being disturbed.

As you can tell from this photo, dotterels can be hard to see – their colouring is so similar to the background of sand, shells and dune vegetation that they merge with their environment. Their nests are often just a scrape in the sand so, to distract intruders who stray too close, dotterels fake injury, perhaps a broken wing, to draw the intruder away from their vulnerable eggs and chicks.

I always think of oystercatchers as completely black but the Variable oystercatcher is just that, variable in colour – some adults have dark uppers, white unders, and smudgy grey bits as well. Their long orange-red beaks and eye-rings are very distinctive, and the birds can often be found in pairs – they usually mate for life – on beaches throughout New Zealand. 

With a name like oystercatcher, you’d expect these shorebirds to feast in style, exclusively on oysters, but they actually eat all types of molluscs, as well as crabs and worms. Their long beaks are particularly well designed for punching holes into mollusc shells and levering apart the two shells of bivalves.

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