Above: An Auckland Island merganser Mergus australis family.
Image: Permission of Peter Schouten
A reluctant flier .....
Auckland Island merganser showed signs of reduced power of flight and the beginning of flightlessness. It's wings were small, but it could still fly. Hunters found it difficult to flush. When disturbed, it preferred to hide instead of taking flight.
The tameness of merganser, reluctance to fly, and a small clutch size is consistent with many New Zealand indigenous birds, and most probably contributed to its' decline.
It was mainly a freshwater species, foraging in inland creeks and streams, but it also inhabited estuaries and was sometimes found in sheltered bays.
Merganser had a long, narrow bill with a hooked tip that turned down. The edges of the upper and lower mandibles were serrated, suited to catching its principal food of small fish. Shellfish and marine worms were also part of the diet.
Merganser have some morphological characteristics of diving ducks, with large webbed feet set back on the body providing strong paddling power.
The Merganser name comes from the latin words "mergus" which referred to diving waterfowl, and "anser" which means goose.
World's five Mergus species .....
The Auckland Island merganser could be one of a small number of New Zealand birds that have been exceptional colonisations from the Northern Hemisphere. Mergus australis has its closest relative in Mergus squamatus of China (Kear & Scarlett 1970).
There are four living species of the Mergus genus worldwide. The only other species of the southern hemisphere is the Brazilian merganser M. octosetaceus which is listed as 'critically endangered' on the IUCN Red List of Threatened Species.
Three species in the northern hemisphere include the red-breasted merganser M. serrator, and common merganser M. merganser which are both migratory and listed as 'least concern'; and the very striking looking scaly-sided merganser M. squamatus of Asia which is 'endangered'.
The Auckland Island merganser was the smallest of all Mergus species, weighing less than a kilogramme, and with a torso length of (20.5 inches)
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