Hawaiian Duck
Encyclopedia
The Hawaiian Duck is a species
of bird
in the family Anatidae
. It is endemic to the large islands of Hawaii
. Some authorities treat it as an island subspecies
of the Mallard
, based on their capacity to produce fertile hybrids, but it appears well distinct and capability of hybridization is meaningless in dabbling duck taxonomy
. The native Hawaiian
name for this duck is koloa maoli.
The former range of the Hawaiian Duck included all of the main Hawaiian islands except the island of Lānai
. Its range is now restricted to the island of Kauai
. The Hawaiian Duck was extirpated on all other islands, but was subsequently reestablished on Oahu
, Hawaii
, and Maui
through release of captive-reared birds. However, all the Hawaiian Ducks in the reestablished populations have bred with feral Mallard
ducks and have produced hybrid offspring that is fully fertile (Griffin et al. 1989); consequently, "pure" Hawaiian Ducks are still only found on Kauai. Kauai has experienced a loss of lowland wetland habitat, in turn affecting the Hawaiian ducks.
Males, 19-20" (some 50 cm) long, are bigger than females, (16-17" or about 45 cm). Both sexes are mottled brown in color, resembling a female Mallard. The speculum feathers
are greenish-blue, bordered on both sides by white. The tail is dark overall, unlike the black-and-white tail of a mallard. The adult male has a darker head and neck which is also sometimes green. A first-year male koloa maoli looks like an eclipse-plumaged male Mallard. The feet and legs are orange. The bill
is olive green in the male and dull orange with dark markings in the female. Another difference between the Hawaiian Duck and the Mallard is its call: the koloa maoli quacks like a Mallard, however not as harsh and vocal. Instead, the vocalization is softer than a Mallard's.
The Hawaiian Duck is a very wary bird often found in pairs instead of large groups. They are very secretive birds and do not associate with other animals much. They occur in lowland wetlands, river valleys, and mountain streams, not adapting too well to human-modified habitat
. Its diet consists of freshwater vegetation, mollusks, insects, and other aquatic invertebrate
s. Some pairs nest year round, but the primary breeding season is from December to May during which pairs are often engaged in spectacular nuptial flights. Two to ten eggs are laid in a well-concealed nest lined with down and breast feathers. Soon after hatching, the young can take to the water but cannot fly until about nine weeks of age.
The Hawaiian duck's population is affected by habitat loss, modifications to wetland habitats for flood control, non-native invasive plants, diseases, environmental contaminants, and predation. Predation threats to the koloa maoli include feral
cat
s, rat
s, and Small Asian Mongooses, which eat the eggs and young. Interbreeding with feral Mallards is also a major problem, as the hybrids seem to be less well-adapted to the local ecosystem. This interbreeding is rather common due to the high numbers of feral Mallards. Several attempted reintroductions have already failed due to the hybrid ducks produced in captivity faring badly in the wild (Rhymer & Simberloff 1996). The "conversion of flooded taro fields to dry sugar-cane acreage" destroys parts of this species' habitat.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
in the family Anatidae
Anatidae
Anatidae is the biological family of birds that includes ducks, geese and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica and on most of the world's islands and island groups...
. It is endemic to the large islands of Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. Some authorities treat it as an island subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
, based on their capacity to produce fertile hybrids, but it appears well distinct and capability of hybridization is meaningless in dabbling duck taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
. The native Hawaiian
Hawaiian language
The Hawaiian language is a Polynesian language that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language of the state of Hawaii...
name for this duck is koloa maoli.
The former range of the Hawaiian Duck included all of the main Hawaiian islands except the island of Lānai
Lanai
Lānai or Lanai is the sixth-largest of the Hawaiian Islands. It is also known as the Pineapple Island because of its past as an island-wide pineapple plantation. The only town is Lānai City, a small settlement....
. Its range is now restricted to the island of Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
. The Hawaiian Duck was extirpated on all other islands, but was subsequently reestablished on Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
, Hawaii
Hawaii (island)
The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...
, and Maui
Maui
The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
through release of captive-reared birds. However, all the Hawaiian Ducks in the reestablished populations have bred with feral Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
ducks and have produced hybrid offspring that is fully fertile (Griffin et al. 1989); consequently, "pure" Hawaiian Ducks are still only found on Kauai. Kauai has experienced a loss of lowland wetland habitat, in turn affecting the Hawaiian ducks.
Males, 19-20" (some 50 cm) long, are bigger than females, (16-17" or about 45 cm). Both sexes are mottled brown in color, resembling a female Mallard. The speculum feathers
Speculum feathers
The speculum is a patch, often distinctly coloured, on the inner remiges of some birds.Examples of the colour of the speculum in a number of ducks are:* Common Teal and Green-winged Teal: Iridescent green edged with buff....
are greenish-blue, bordered on both sides by white. The tail is dark overall, unlike the black-and-white tail of a mallard. The adult male has a darker head and neck which is also sometimes green. A first-year male koloa maoli looks like an eclipse-plumaged male Mallard. The feet and legs are orange. The bill
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
is olive green in the male and dull orange with dark markings in the female. Another difference between the Hawaiian Duck and the Mallard is its call: the koloa maoli quacks like a Mallard, however not as harsh and vocal. Instead, the vocalization is softer than a Mallard's.
The Hawaiian Duck is a very wary bird often found in pairs instead of large groups. They are very secretive birds and do not associate with other animals much. They occur in lowland wetlands, river valleys, and mountain streams, not adapting too well to human-modified habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. Its diet consists of freshwater vegetation, mollusks, insects, and other aquatic invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. Some pairs nest year round, but the primary breeding season is from December to May during which pairs are often engaged in spectacular nuptial flights. Two to ten eggs are laid in a well-concealed nest lined with down and breast feathers. Soon after hatching, the young can take to the water but cannot fly until about nine weeks of age.
The Hawaiian duck's population is affected by habitat loss, modifications to wetland habitats for flood control, non-native invasive plants, diseases, environmental contaminants, and predation. Predation threats to the koloa maoli include feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...
cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s, and Small Asian Mongooses, which eat the eggs and young. Interbreeding with feral Mallards is also a major problem, as the hybrids seem to be less well-adapted to the local ecosystem. This interbreeding is rather common due to the high numbers of feral Mallards. Several attempted reintroductions have already failed due to the hybrid ducks produced in captivity faring badly in the wild (Rhymer & Simberloff 1996). The "conversion of flooded taro fields to dry sugar-cane acreage" destroys parts of this species' habitat.