ARTICLES ON HAWAIIAN AND PACIFIC BIRDS, BIRDWATCHING AND WILDLIFE

The Rise and Fall of the Fulvous Whistling-Duck in Hawai'i

The Fulvous Whistling-Duck or Fulvous Tree-Duck (Dendrocygna bicolor) is found in southern North America and South America as far as Argentina and from East Africa west to India in its natural range. A few small populations of introduced birds exist elsewhere as well. Within the U.S., Fulvous Whistling-Ducks live on the Gulf coast of Texas and Louisiana, Southern California, and have expanded their range to include Hawaii and the Atlantic coast of Florida. They are common vagrants north of their range (Kaufman, 1996). Range expansion is attributed to development of new rice production areas (Turnbull et al., 1989 ). The population size is declining in the southwest and increasing in the southeast (Kaufman, 1996).

This species is most commonly found in fresh and brackish coastal marshes, as well as agricultural fields (Peterson, 1980; Ehrlich et al., 1988; Kaufman, 1996). They build a nest of woven grasses on the ground next to water or several feet up in the vegetation of a marsh. The clutch size ranges from 6-16 white eggs, though nests with many more eggs are found due to egg dumping (Kaufman, 1996). Young are precocial, can swim and dive well, and obtain their own food, but parents are present (Kaufman, 1996). The maximum age of a Fulvous Whistling-Duck recorded in nature is 6 years and 6 months. The species wanders over broad areas in flocks. The Gulf Coast population migrates to Mexico in the winter (Kaufman, 1996). The species feeds primarily on seed and grain, but also ingest a small amount of insects, snails, and invertebrates. Feeding often occurs at night in shallow water, and on land, including agricultural fields, prairies, and pastures (Kaufman, 1996; Ehrlich et al., 1988).

Figure 1. Summer distribution of Fulvous Whistling-Ducks in North America. Map taken from Patuxent Wildlife Research Center

Figure 2. Winter distribution of Fulvous Whistling-Ducks in North America. Map taken from Patuxent Wildlife Research Center

The species was first noticed in the Kahuku area of O'ahu in the Hawaiian Islands on 6th January 1982, where six adult birds were counted by Robert Shallenberger and David Woodside of the U.S. Fish and Wildlife Service during the winter waterfowl count at the Punamano Unit of the James Campbell NWR, and on the 9th January, six birds were again sighted. In June of 1982, two adult ducks were observed at the Ki'i Unit of the James Campbell NWR. Two birds, probably the same individuals, were seen regularly between 1982 and early 1984 at Ki'i and nearby Amorient Prawn Farm. On an outing sponsored by the Foster Botanic Gardens on 13th April 1984, seven birds were observed flying around and landing in the Ki'i ponds area. Peter Donaldson sighted nine whistling ducks at the same ponds on 16th April. Between April and July 1984 groups of two, three, four, or five birds were seen, but never as many as seven or nine.

On 25th July 1984 Peter Donaldson saw three adults with a group of 16 recently hatched chicks in one of theAmorient Prawn Farm ponds adjacent to the James Campbell NWR. This is the first known observation of breeding activity of Fulvous Whistling- Ducks in the wild in Hawai'i. On the following day, 26th July at James Campbell NWR, two adult Whistling-Ducks were observed with a group of ten young in one of the canals of the Ki'i Unit. The young were very small, probably not more than 3 to 4 days old, and the distance between the above two sightings is about 0.2 Km, and were possibly the same brood.
On 27th July, David Woodside saw 16 young with two adults, also at the Ki'i unit where they had been seen the previous day. On 28th July, at the nearby Amorient ponds, Bob Pyle and Andy Engilis sighted three adults with 15 young and another adult pair with a single young. At the monthly waterfowl count on 1st August, Peter Pyle, David Woodside and Jim Krakowski saw five adults with sixteen young also at the nearby Amorient ponds. It is uncertain whether the groups of ten and sixteen young observed at different times were the same birds or different broods. This was the second record of a migrant duck species breeding in the Hawaiian Islands. From this the species built up a small self-supporting population.

Typical clutch size for Fulvous Whistling-Ducks ranges from 10 to 15 eggs, but sometimes 30 to 100 eggs are laid by several females in the same nest, making brood size and parent/offspring associations difficult to assess.

Three sightings of Fulvous Whistling-Ducks also were made on the island of Kaua'i between 1983 and 1984. Peter Donaldson saw one whistling-duck at the Hanalei NWR on 8 November. 1983. Jim Krakowski sighted a pair of whistling-ducks on the Waialua River, at Paradise Pacifica near Kapa'a, and a single duck on an impoundment of the Hanalei NWR in the summer of 1984.

In 1986, N. Jack Leishman hypothesised about the origins of the species in Hawai'i and commented on the effect that Whistling-Ducks may have on the endemic waterbirds in the Islands "The presence of the Fulvous Whistling-Duck in Hawai'i leads to a number of questions concerning its arrival in the islands, its potential for population increase throughout the islands, and possible competitive interactions with other native waterbirds. particularly the Koloa (Anas wyvilliana), Hawaiian Gallinule (Gallinula chloropus sandvicensis) and Hawaiian Coot (Fulica amerirana alai). The first question, unanswered at this time is: is the arrival of the whistling-duck a natural occurence or is it an escape from someone's domestic stock? There is currently a serious lack of monitoring of potential pest species in Hawai'i, especially animals being kept as pets or being raised for food. There is a need for increased effort on the part of the Department of Land and Natural Resources, State Department of Agriculture, and other involved and affected agencies to determine which wildlife species are being raised and whether these captive birds ever interact with native bird populations. Because of their extensive range and ability to fly long distances, it is possible the Fulvous Whistling-Duck arrived in Hawai'i on its own, and has become a new member of the indigenous fauna. This can not be argued adequately until a thorough inventory is made of birds held caged or captive in the State. Whether indigenous or newly introduced, two questions will be prominent regarding management strategies involving this species. First, what is their potential for population increase in Hawai'i and second, how will this affect other native waterbirds? On the mainland Fulvous Whistling-Ducks breed in fresh-water marshes in areas of dense vegetation such as cattails or rice fields, especially where dense weedy vegetation is present (Johnsgard 1975). The pond perimeters and canals at the James Campbell NWR appear to be ideal nesting habitat. One endemic species and two endemic subspecies of endangered waterbird that may interact with Fulvous Whistling-Ducks also inhabit this area: the Koloa or Hawaiian Duck; Hawaiian Gallinule: and Hawaiian Coot.

Although the favored habitat of Koloa is mountain streams (Berger 1981), they are still found in what remains of lowland wetland habitats. Feeding competition between the two duck species might occur if the whistling-duck population were to substantially increase. Competition for nesting sites, however, would probably be minimal to non-existant since Koloa are a ground nesting species (Berger 1981) while the Fulvous Whistling-Duck nests in emergent wetland vegetation (Delacour 1954).
Since the Hawaiian Gallinule nests in areas similar to those favored by the whistling-duck (Berger 1981), an increase in the whistling-duck population could pose a competitive threat to the extant gallinule population. The Hawaiian Coot is usually observed to be a platform nester in open water areas, although a few individuals have been observed to nest in emergent vegetation, the same as the American Coot on the mainland, and thus could compete with the whistling-duck for nesting space (Jim Krakowski. pers. comm.). Irrespective of the mode of arrival in the Hawaiian Islands, the Fulvous Whistling-Duck should be monitored closely to assess its breeding status and interactions with native species. Previous experience with escaped and purposely introduced organisms in Hawai'i has shown clearly that negative ramifications on the biota and ecosystems can occur."

By 1990 the population stood at 30 or so birds and the species was recorded from other islands in the chain, such as Kaua'i (mentioned above), Moloka'i and Maui. However, by the late 1990's only three birds remained and the last individual, known locally as "Lonesome George" was (probably) last observed on 1st December 2001. No other "wild" Fulvous Whistling-Ducks have been recorded in Hawai'i during the remainder of 2001 or 2002, and so the species is presumed extinct in the Hawaiian Islands.

The Kahuku area of O'ahu is the site of two important wetland areas, James Campbell National Wildlife Refuge and the Kahuku Shrimp Ponds / Amoriant Aquafarm. The habitat provided by these two sites presumably played an important part in the colonisation of the area by the Whistling-Ducks. The subsequent decline and temporary closure of the aquafarm/shrimpfarm in the late 1990's is thought to have played a significant part in the decline and ultimate extinction of the Ducks in the State, although it seems unlikely that this was the only factor which affected the species demise.

Thanks to Peter Donaldson for providing the 'Elepaio article on Fulvous Whistling-Ducks.

References:

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ENGILIS, Jr, A. and T.K. PRATT. 1993. Status and population trends of Hawaii's native Waterbirds, 1977-1987. Wilson Bulletin, vol. 105 (1) pp 142-158.

ENGILIS, Jr., A. 1987. Surveys and inventories of waterbirds in the state of Hawaii. Progress report job No. R-III-A, project No. W-18-R-12. Division of Forestry and Wildlife, Honolulu. 48pp.

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TURNBULL, R.E., JOHNSON, F.A. and BRAKHAGE, D.H. 1989. Status, distribution and foods of Fulvous Whistling-Duck in South Florida. Journal of Wildlife Management 53 (4), 1046-1051.

U.S. FISH AND WILDLIFE SERVICE. 1994. Draft Revised Recovery Plan for Hawaiian Waterbirds. Second revision: Hawaiian Duck or Koloa, Hawaiian Coot, Hawaiian Moorhen and Hawaiian Stilt. U.S. Fish and Wildlife Service, Portland, OR. 96pp.

U.S. FISH AND WILDLIFE SERVICE. 1999. Draft Revised Recovery plan for Hawaiian Waterbirds, second revision. U.S. Fish and Wildlife Service, Portland OR. 107pp

U.S.G.S. Patuxent Wildlife Research Center. 1999. The Fulvous-Whistling Duck. USGS, Maryland, USA. From website: http://www.pwrc.usgs.gov/

Christian Melgar, Worthing, West Sussex. 2003.

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