Laysan Duck
Encyclopedia
The Laysan Duck also known as the Laysan Teal because of its small size, is an endangered dabbling duck
endemic to the Hawaiian Islands
. Fossil
evidence reveals that Laysan Ducks once lived across the entire archipelago, but today survive only on three small, isolated island
s.
island, one of the Northwestern Hawaiian Islands
. It is a member of the mallard
clade
of dabbling ducks, and is a highly behaviorally and genetically unusual species. Recent evidence suggests they evolved from an east Asian, southern hemisphere ancestor of mallards, not from stray migratory Mallards (Anas platyrhynchos) as had been reported in the past.
) in both sexes. Leucistism, or extensive white feathering, is common on the head and neck of older birds. The legs and feet are orange, usually brighter in the male. The annual pre-basic molt is complete, and the ducks lose all their flight feathers and become incapable of flight until new feathers grow in. Wild ducks have been known to live to the age of twelve years, and captive birds have lived to the age of eighteen.
, algae
, leaves, and seeds. During the day, and especially in the breeding season, they prefer to hide among the grass and shrub vegetation, helping them to avoid avian predators such as frigatebird
s. They prefer to venture out in the open and feed on the lake from dusk til dawn, although there seems to be marked variation from year to year according to the availability of food items.
building begins in spring. The female builds a well-concealed nest on the ground below dense vegetation, especially Eragrostis variabilis bunchgrass. The nest is a shallow bowl lined with dead grass and down feathers. Egg-laying typically occurs from April to August. Average clutch size on Laysan Island is approximately four eggs
. The newly established population on Midway lays larger clutches. Ducklings are precocious and feed on their own day two after hatching, but are guarded, brooded, and led to foraging sites by the hen for approximately 40 to 60 days.
and associated non-native mammalian predators. By 1860, the ducks disappeared from all but Laysan Island (the duck’s namesake), most likely due to predation by introduced rats. Like many isolated island species, the Laysan Duck evolved in an environment lacking mammalian predators, and is ill-suited
to defend itself against non-native ground hunters, such as humans, rat
s, pigs, and Small Asian Mongooses. For example, Laysan Ducks are more likely to freeze their movement rather than flush or fly when startled— a strategy well suited for cryptic defense against Hawaii’s native flying predators, but ineffective against ground predators. Although the non-migratory Laysan Duck can fly, it does not disperse between islands.
The Laysan Duck found refuge through most of the nineteenth century on rat-free Laysan Island, surviving within the smallest geographic range of any duck species worldwide (415 hectares (1.6 sq mi)). Laysan Island gained federal protection in 1909, with the establishment of the Hawaiian Islands National Wildlife Refuge. However, devastation of the island’s vegetation by introduced domestic rabbit
s brought the duck to the brink of extinction in 1912, with an all-time low population of 7 adults and five juveniles.
s starved and the remaining ones were eradicated by biologists in 1923, the ducks began to recover, increasing to a population of about 500 individuals by the 1950s. Congress passed the Endangered Species Preservation Act in 1966, and in 1967 the Laysan Duck was declared an endangered species with federal protection. However, population bottlenecks occurred, such as the severe 1993 El Niño drought and food shortage, which reduced the number of ducks to about 100. Today, breeding and survival of the birds is closely tracked. Since 1998, a sample of birds have been fitted with unique leg bands
or radio transmitters for monitoring reproductive success and survival, revealing that typically only 30% of ducklings on Laysan Island survive to fledge. In 2004, the population grew to an estimated 576 ducks.
In October 2004 and 2005, 42 Laysan Ducks were translocated to Midway Atoll National Wildlife Refuge
as a collaborative effort between the United States Geological Survey
and Fish and Wildlife Service
to restore a second population of ducks in the wild. The creation of a second population, since disaster is unlikely to strike both atolls simultaneously, reduces the risk of extinction by random catastrophes such as drought, hurricanes, tsunamis, disease outbreaks (like avian influenza), and accidental introductions of non-native plants and animals.
The second “insurance” population of Laysan Ducks on Midway has grown quickly, more than doubling in size within the first two years (USGS 2006c). As of January 2007, 100 ducks call Midway’s Sand and Eastern Island home. Researchers monitoring the Midway population have found that the ducks are breeding at an earlier age, and laying more eggs than birds on Laysan. This suggests that the abundant habitat and food available on Midway has stimulated greater reproductive effort in the ducks, which contributes optimism for the success of this re-introduced population.
. Even a slight rise in sea level would destroy a large portion of the duck’s current habitat. The spread of parasites such as the nematode
Echinuria uncinata could be extremely pathogenic, as well as the introduction of disease by migratory waterfowl along the Pacific Flyway
(such as avian influenza, avian malaria
, cholera
, botulism
and duck plague
). Environmental catastrophes such as drought, severe storms, and tsunamis may decimate populations. The increased frequency and severity of storms are an anticipated effect of global warming.
A recovery plan for the Laysan Duck has been developed by the U.S. Fish and Wildlife Service. The goal of the recovery program is to conserve and recover the species to the extent that it may be down-listed from endangered to threatened in the near future, and ultimately, that the population be healthy enough to no longer require federal protection under the Endangered Species Act
. The emphasis of the recovery plan is the distribution of additional viable populations in the Laysan Duck’s historical and prehistorical range. The creation of multiple populations will decrease the risk that catastrophic events will result in species extinction. The increase of population size will diminish the threats from demographic and environmental uncertainties. To achieve this goal, biologists plan to establish at least five populations on a combination of predator-free Northwestern Hawaiian Islands and predator-controlled sites on Main Hawaiian Islands. This plan includes wild translocation and the establishment of a successful captive or semi-captive breeding program using wild source eggs for reintroductions to the Main Hawaiian Islands. Additionally, the plan calls for achieving gene flow
between the wild source populations through long-term inter-island translocations, and island-specific management for each population to reduce threats and improve quality of habitat. If basic criteria of the recovery plan are met, the Laysan Duck could be down-listed from endangered to threatened by 2019.
Anatinae
The Anatinae is a subfamily of the family Anatidae . Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving...
endemic to the Hawaiian Islands
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
evidence reveals that Laysan Ducks once lived across the entire archipelago, but today survive only on three small, isolated island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s.
Taxonomy
Named by Lionel Walter Rothschild in 1892, the Laysan Duck is named after LaysanLaysan
Laysan , located northwest of Honolulu at N25° 42' 14" W171° 44' 04", is one of the Northwestern Hawaiian Islands. It comprises one land mass of , about 1 by 1.5 miles in size . It is an atoll of sorts, although the land completely surrounds a shallow central lake some above sea level that has...
island, one of the Northwestern Hawaiian Islands
Northwestern Hawaiian Islands
The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...
. It is a member 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....
clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of dabbling ducks, and is a highly behaviorally and genetically unusual species. Recent evidence suggests they evolved from an east Asian, southern hemisphere ancestor of mallards, not from stray migratory Mallards (Anas platyrhynchos) as had been reported in the past.
Description
The Laysan Duck is teal-sized and dark brown, with a prominent white eye-ring. The bill is short and spatulate, dark green with variable black blotching in males, and dull orange with variable black blotching in females. The Laysan Duck usually has a ring of fat around its neck. Some males show faint iridescence on the head or neck and have slightly upturned central tail feathers. The wing has an iridescent purplish-green patch (speculum feathersSpeculum 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....
) in both sexes. Leucistism, or extensive white feathering, is common on the head and neck of older birds. The legs and feet are orange, usually brighter in the male. The annual pre-basic molt is complete, and the ducks lose all their flight feathers and become incapable of flight until new feathers grow in. Wild ducks have been known to live to the age of twelve years, and captive birds have lived to the age of eighteen.
Behavior
The Laysan Duck walks and runs well, with a pelvic girdle adapted to terrestrial foraging. Energetic foraging behavior includes a fly-snapping sprint through Neoscatella sexnotata brine fly swarms. With necks outstretched, and bills close to the ground, the ducks run along a mudflat and as clouds of flies rise up in front, snap them up by rapidly opening and closing their bills. The ducks also will dabble and filter feed along lake shallows, shore, and in upland vegetation for macroinvertebratesInvertebrate
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...
, algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
, leaves, and seeds. During the day, and especially in the breeding season, they prefer to hide among the grass and shrub vegetation, helping them to avoid avian predators such as frigatebird
Frigatebird
The frigatebirds are a family, Fregatidae, of seabirds. There are five species in the single genus Fregata. They are also sometimes called Man of War birds or Pirate birds. Since they are related to the pelicans, the term "frigate pelican" is also a name applied to them...
s. They prefer to venture out in the open and feed on the lake from dusk til dawn, although there seems to be marked variation from year to year according to the availability of food items.
Reproduction
Pair formation begins in fall, and nestBird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
building begins in spring. The female builds a well-concealed nest on the ground below dense vegetation, especially Eragrostis variabilis bunchgrass. The nest is a shallow bowl lined with dead grass and down feathers. Egg-laying typically occurs from April to August. Average clutch size on Laysan Island is approximately four eggs
Bird egg
Bird eggs are laid by females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one to about 17...
. The newly established population on Midway lays larger clutches. Ducklings are precocious and feed on their own day two after hatching, but are guarded, brooded, and led to foraging sites by the hen for approximately 40 to 60 days.
Decline to near-extinction
The decline of the Laysan Duck began 1000-1600 years ago, with the colonization of the Hawaiian Islands by PolynesiansPolynesians
The Polynesian peoples is a grouping of various ethnic groups that speak Polynesian languages, a branch of the Oceanic languages within the Austronesian languages, and inhabit Polynesia. They number approximately 1,500,000 people...
and associated non-native mammalian predators. By 1860, the ducks disappeared from all but Laysan Island (the duck’s namesake), most likely due to predation by introduced rats. Like many isolated island species, the Laysan Duck evolved in an environment lacking mammalian predators, and is ill-suited
Island tameness
Island tameness is the tendency of many populations and species of animals living on isolated islands to lose their wariness of potential predators, particularly of large animals. The term is partly synonymous with ecological naïvete, which also has a wider meaning referring to the loss of...
to defend itself against non-native ground hunters, such as humans, 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, pigs, and Small Asian Mongooses. For example, Laysan Ducks are more likely to freeze their movement rather than flush or fly when startled— a strategy well suited for cryptic defense against Hawaii’s native flying predators, but ineffective against ground predators. Although the non-migratory Laysan Duck can fly, it does not disperse between islands.
The Laysan Duck found refuge through most of the nineteenth century on rat-free Laysan Island, surviving within the smallest geographic range of any duck species worldwide (415 hectares (1.6 sq mi)). Laysan Island gained federal protection in 1909, with the establishment of the Hawaiian Islands National Wildlife Refuge. However, devastation of the island’s vegetation by introduced domestic rabbit
Domestic rabbit
A domestic rabbit, or more commonly known as simply the rabbit, is any of the several varieties of European rabbit that have been domesticated....
s brought the duck to the brink of extinction in 1912, with an all-time low population of 7 adults and five juveniles.
Recovery
After many domestic rabbitDomestic rabbit
A domestic rabbit, or more commonly known as simply the rabbit, is any of the several varieties of European rabbit that have been domesticated....
s starved and the remaining ones were eradicated by biologists in 1923, the ducks began to recover, increasing to a population of about 500 individuals by the 1950s. Congress passed the Endangered Species Preservation Act in 1966, and in 1967 the Laysan Duck was declared an endangered species with federal protection. However, population bottlenecks occurred, such as the severe 1993 El Niño drought and food shortage, which reduced the number of ducks to about 100. Today, breeding and survival of the birds is closely tracked. Since 1998, a sample of birds have been fitted with unique leg bands
Bird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
or radio transmitters for monitoring reproductive success and survival, revealing that typically only 30% of ducklings on Laysan Island survive to fledge. In 2004, the population grew to an estimated 576 ducks.
Midway Atoll
Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...
as a collaborative effort between the United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
and Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
to restore a second population of ducks in the wild. The creation of a second population, since disaster is unlikely to strike both atolls simultaneously, reduces the risk of extinction by random catastrophes such as drought, hurricanes, tsunamis, disease outbreaks (like avian influenza), and accidental introductions of non-native plants and animals.
The second “insurance” population of Laysan Ducks on Midway has grown quickly, more than doubling in size within the first two years (USGS 2006c). As of January 2007, 100 ducks call Midway’s Sand and Eastern Island home. Researchers monitoring the Midway population have found that the ducks are breeding at an earlier age, and laying more eggs than birds on Laysan. This suggests that the abundant habitat and food available on Midway has stimulated greater reproductive effort in the ducks, which contributes optimism for the success of this re-introduced population.
Future outlook
The persistence of the Laysan Duck into the future is optimistic, though threats to the population remain. Threats include the introduction of non-native species, which may change vital rates, displace native species and adversely affect nesting and foraging opportunities. Devastation to vegetation could increase sedimentation of the lakes and seeps that serve as important foraging habitat. Human disturbance may impact nesting and brooding, and landing permits to the Laysan Island refuge are granted only for official or scientific purposes. Debris and contaminants washed ashore by ocean currents could pose a serious threat to the duck. Pesticide containers and oil spills have contaminated Laysan in the past. The island homes of the duck are especially vulnerable to a rise in sea level and extreme weather associated with global warmingGlobal warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
. Even a slight rise in sea level would destroy a large portion of the duck’s current habitat. The spread of parasites such as the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
Echinuria uncinata could be extremely pathogenic, as well as the introduction of disease by migratory waterfowl along the Pacific Flyway
Pacific Flyway
The Pacific Flyway is a major north-south route of travel for migratory birds in America, extending from Alaska to Patagonia. Every year, migratory birds travel some or all of this distance both in spring and in fall, following food sources, heading to breeding grounds, or travelling to...
(such as avian influenza, avian malaria
Avian malaria
Avian malaria is a parasitic disease of birds.-Etiology:Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in tropical regions...
, cholera
Cholera
Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...
, botulism
Botulism
Botulism also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin which is metabolic waste produced under anaerobic conditions by the bacterium Clostridium botulinum, and affecting a wide range of mammals, birds and fish...
and duck plague
Duck plague
-Introduction:Duck plague is a worldwide disease caused by duck herpesvirus 1 of the family Herpesviridae that causes acute disease with high mortality rates in flocks of ducks, geese and swans. It is spread both vertically and horizontally - through contaminated water and direct contact...
). Environmental catastrophes such as drought, severe storms, and tsunamis may decimate populations. The increased frequency and severity of storms are an anticipated effect of global warming.
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
. The emphasis of the recovery plan is the distribution of additional viable populations in the Laysan Duck’s historical and prehistorical range. The creation of multiple populations will decrease the risk that catastrophic events will result in species extinction. The increase of population size will diminish the threats from demographic and environmental uncertainties. To achieve this goal, biologists plan to establish at least five populations on a combination of predator-free Northwestern Hawaiian Islands and predator-controlled sites on Main Hawaiian Islands. This plan includes wild translocation and the establishment of a successful captive or semi-captive breeding program using wild source eggs for reintroductions to the Main Hawaiian Islands. Additionally, the plan calls for achieving gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
between the wild source populations through long-term inter-island translocations, and island-specific management for each population to reduce threats and improve quality of habitat. If basic criteria of the recovery plan are met, the Laysan Duck could be down-listed from endangered to threatened by 2019.