By Dr. Cynthia H. Holte PAGO PAGO, American Samoa (The Samoa News, July 11, 2010) - The grey duck (also known as the Pacific black duck, scientific name - Anas superciliosa), or Toloa, is American Samoa’s only duck.

The number of individuals observed across the Territory has fluctuated between zero (results from a 1986 survey by Enbring and Ramsey of the US Fish and Wildlife Service) to over 40 (observed by DMWR [Department of Marine and Wildlife Services] personnel in Faimulivai marsh on Aunu’u in 1995).

For the past 10 years, subsequent surveys by DMWR personnel conducted on Aunu’u (Pala Lake and Faimulivai) report an average of 6 animals per sighting (range 2 – 10). In the past 10 months, grey ducks have also been seen in the village of Malaeloa on Tutuila.

There may also be ducks on Manua and Swains, but sightings there have not been confirmed. There are no recorded observations anywhere in the Territory, past or present, of juvenile ducks or ducklings.

[PIR editor’s note: Hawaii’s endangered Koloa Maoli duck has increased in population with captive breeding and releases into the wild but the Koloa has bred with feral mallard ducks, producing a hybrid. The only pure Koloa in Hawaii today are found on the Island of Kauai. ]

For over 20 years the number of grey ducks in American Samoa has consistently remained low (other than sightings from the mid 1990’s). We have no definitive knowledge of what prevents the number of grey ducks in the Territory from expanding. We also do not know whether the reduction in animals observed since the mid 1990’s is the result of lower survivorship and reproduction or whether ducks have relocated elsewhere.

The possibility exists that at any one time we are seeing only a portion of the population i.e. rather than congregating at the same place ducks are distributed across multiple sites in the Territory. We do know that duck numbers have been restricted due to hunting and loss of habitat; invasive species such as rats or domestic animals such as dogs and cats, may also take their toll by preying on eggs, ducklings, or even adults.

The Wildlife Division of the DMWR has undertaken an investigation of grey duck ecology within the Territory. Ailaoa Tualualelei and Cynthia Holte recently returned from Peacock Springs, New Zealand where they met with individuals involved in the conservation of another duck— the brown teal.

The purpose of their visit was to gain experience in handling ducks and outfitting them with a special type of radio transmitter, which is attached via a backpack.

The Department’s goals are to capture a few grey ducks and outfit them with similar transmitters so as to monitor their movements.

Questions to be answered include:

Eventually the DMWR hopes to learn more about the life stages of the ducks such as where are all the ducklings? We invite comments and observations from anyone that has knowledge of this animal and who may have observed grey ducks elsewhere than previously mentioned in this article.

Dr. Cynthia Holte is a biologist with the American Samoa Department of Marine and Wildlife Services

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