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Duck, Laysan

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Description

The Laysan duck has mottled chestnut brown plumage across most of its body. It has a dirty, undefined white ring around its eye and a variable amount of white on the rest of its head and neck, as well as bright orange legs and feet.

Cover photo: Adult Laysan Duck by Mark Pressler

Classification

Overview
The Laysan duck is a bird in the Anseriformes, or waterfowl order. Until fairly recently, this duck was considered a subspecies of the mallard. However, recent genetic evidence has shown that it is distinct enough to be considered its own speices.
Class
Aves
Order
Anseriformes
Family
Anatidae
Genus
Anas
Species
A. laysanensis

Key Facts

Conservation Status
Critically Endangered
Lifespan
~12 years in the wild, anecdotal reports of individuals up to 18 years old under human care
Height
15 – 17 in (38.1 – 43.2 cm)
Weight
0.93 – 1.1 lbs (420 – 500 g)
Wingspan
Unknown. Similarly sized ducks have a wingspan of ~1.8 – 2.3 ft (55 – 70 cm)

The IUCN Red List classifies the Lasyan Duck as Critically Endangered. It is considered the rarest duck that is native to part of the United States. This duck has a impressive story of conservation and survival, and was very close to extinction about 100 years ago. Now, thanks to extensive conservation efforts as well as some amount of luck, their population has increased. However, this population still fluctuates wildly due to natural disasters and disease, and does not have the stability needed for scientists to consider this duck safe from extinction.

Osteological records have shown us that historically, Laysan ducks were found on most, if not all islands along the Hawaiian archipelago. As Polynesian expansion occurred around 400 – 1000 AD, non-native mammals such as rats were introduced to the main Hawaiian islands and the Laysan duck disappeared. The final stronghold of this duck was Laysan, a small island in the Hawaiian archipelago between the main islands and Midway.

From about 1891 – 1904, western guano miners ravaged the ecology of Laysan. Humans did not have a way to efficiently synthetically fix nitrogen and create ammonia for explosives and fertilizer until the development of the Haber-Bosch process during World War 1. Before this, the excrement of bats and seabirds, also known as guano, was highly valued for its ammonia content. During the 13 year period that guano miners were present on Laysan, they shot Laysan ducks for food and sport. In 1902, the population of the Laysan duck was estimated to be less than 100 individuals. But, the final and worst blow to the duck was the rabbits that were released onto the island for food, a common practice of colonizers at the time.

By 1909, guano mining had ceased on Laysan and it was declared part of the Hawaiian Islands Bird Reservation. But even though the miners had left, the rabbits remained. Expeditions in 1911 and 1912 found thousands of rabbits, deteriorating vegetation, and only 7 Laysan ducks. By the time an expedition was sent to remove rabbits from the island in 1923, the island was almost completely barren. The Laysan rail, Laysan millerbird, and Laysan honeycreeper had all gone extinct as their habitat disappeared. Only 20 Laysan ducks were counted, and this was likely the entire population, as there was no remaining vegetation for them to hide in. There were only hundreds, rather than thousands of rabbits on the island now due to a lack of food, and complete rabbit removal was successful during this 1923 expedition.

A return expedition in 1936 found that Laysan was covered in vegetation once again, although the palms and sandalwood trees previously found on the island never returned. Miraculously, that tiny population of Laysan ducks managed to survive as well, and a 1950 count found 33 individuals. The population continued to grow as the island returned to a healthier state, and a population estimate in 1980 with more rigorous surveying protocols was ~510 ducks. Since then, the population has fluctuated between ~100 – 700 individuals due to winter storms, tsunamis, and outbreaks of avian botulism. In order to not have all of the Laysan duck eggs in one island basket, Laysan ducks were also reintroduced to Midway Atoll in 2005 and Kure Atoll in 2014.

Laysan is now part of the North-western Hawaiian Islands National Wildlife Refuge and was designated as a Research Natural Area by the US Fish & Wildlife Service in 1967. This means that the island is only open for scientific research and monitoring. While the population on Laysan island is currently relatively stable, scientists continue to monitor these ducks—a significant natural disaster, disease outbreak, or predator introduction could quickly disrupt this stability. Conservationists will likely step in with more intensive management if invasive mammals regain a foothold on the island, if the critical central lake is becoming filled with blowing sand, or if the critical vegetation on the island is damaged.

Social Life
The ~500 – 700 Laysan ducks on their small island home will congregate for activities such as drinking from freshwater seeps and courtship, and will disperse for activities such as feeding. These ducks pair-bond, but males do not take part in the rearing of offspring and are only together with their partner during courtship and after either brood rearing success or failure. Pairs were observed staying together about half the time from one nesting season to the next.

Habitat and Range
Laysan ducks were historically found along the entire Hawaiian archipelago, but their range was reduced to only the island of Laysan, which is a small island in the Hawaiian archipelago about 1000 miles northwest of Oahu. As part of conservation efforts, they have now been reintroduced to Midway Atoll in 2005 and Kure Atoll in 2014.

Laysan island is only about 1 mile (1.6 km) wide and 1.5 (2.9 km) miles long, and has a large central lake. There were historically sandalwood trees and fan palms on the island, but there are now no trees, only an introduced shrub and a mix of herbaceous plants. Laysan ducks utilize all of this habitat, moving between the lake and various vegetation areas depending on their food, water, and nesting needs.

Diet
Laysan ducks are dabbling ducks, largely feeding on invertebrates near the surface of Laysan lake, as well as aquatic plants and seeds. These ducks have also been observed running through large swarms of brine flies and grabbing the flies out of the air as they go.

Predators
The Laysan duck evolved around avian predators but did not evolve around ground-dwelling predators, evidenced by their tendency to freeze in place when threatened, which is effective when a threat is above, but less so when a threat is right next to them. Currently, larger seabirds such as frigatebirds may prey upon eggs and ducklings, but an adult Laysan duck has no natural predators.

Reproduction
Sexual Maturity:  ~1 year
Nesting Season: mostly April – August, occasionally February – November
Incubation: ~28 days
Clutch Size: usually 4 eggs

Information

Description

The Laysan duck has mottled chestnut brown plumage across most of its body. It has a dirty, undefined white ring around its eye and a variable amount of white on the rest of its head and neck, as well as bright orange legs and feet.

Cover photo: Adult Laysan Duck by Mark Pressler

Classification

Overview
The Laysan duck is a bird in the Anseriformes, or waterfowl order. Until fairly recently, this duck was considered a subspecies of the mallard. However, recent genetic evidence has shown that it is distinct enough to be considered its own speices.
Class
Aves
Order
Anseriformes
Family
Anatidae
Genus
Anas
Species
A. laysanensis

Key Facts

Conservation Status
Critically Endangered
Lifespan
~12 years in the wild, anecdotal reports of individuals up to 18 years old under human care
Height
15 – 17 in (38.1 – 43.2 cm)
Weight
0.93 – 1.1 lbs (420 – 500 g)
Wingspan
Unknown. Similarly sized ducks have a wingspan of ~1.8 – 2.3 ft (55 – 70 cm)

The IUCN Red List classifies the Lasyan Duck as Critically Endangered. It is considered the rarest duck that is native to part of the United States. This duck has a impressive story of conservation and survival, and was very close to extinction about 100 years ago. Now, thanks to extensive conservation efforts as well as some amount of luck, their population has increased. However, this population still fluctuates wildly due to natural disasters and disease, and does not have the stability needed for scientists to consider this duck safe from extinction.

Osteological records have shown us that historically, Laysan ducks were found on most, if not all islands along the Hawaiian archipelago. As Polynesian expansion occurred around 400 – 1000 AD, non-native mammals such as rats were introduced to the main Hawaiian islands and the Laysan duck disappeared. The final stronghold of this duck was Laysan, a small island in the Hawaiian archipelago between the main islands and Midway.

From about 1891 – 1904, western guano miners ravaged the ecology of Laysan. Humans did not have a way to efficiently synthetically fix nitrogen and create ammonia for explosives and fertilizer until the development of the Haber-Bosch process during World War 1. Before this, the excrement of bats and seabirds, also known as guano, was highly valued for its ammonia content. During the 13 year period that guano miners were present on Laysan, they shot Laysan ducks for food and sport. In 1902, the population of the Laysan duck was estimated to be less than 100 individuals. But, the final and worst blow to the duck was the rabbits that were released onto the island for food, a common practice of colonizers at the time.

By 1909, guano mining had ceased on Laysan and it was declared part of the Hawaiian Islands Bird Reservation. But even though the miners had left, the rabbits remained. Expeditions in 1911 and 1912 found thousands of rabbits, deteriorating vegetation, and only 7 Laysan ducks. By the time an expedition was sent to remove rabbits from the island in 1923, the island was almost completely barren. The Laysan rail, Laysan millerbird, and Laysan honeycreeper had all gone extinct as their habitat disappeared. Only 20 Laysan ducks were counted, and this was likely the entire population, as there was no remaining vegetation for them to hide in. There were only hundreds, rather than thousands of rabbits on the island now due to a lack of food, and complete rabbit removal was successful during this 1923 expedition.

A return expedition in 1936 found that Laysan was covered in vegetation once again, although the palms and sandalwood trees previously found on the island never returned. Miraculously, that tiny population of Laysan ducks managed to survive as well, and a 1950 count found 33 individuals. The population continued to grow as the island returned to a healthier state, and a population estimate in 1980 with more rigorous surveying protocols was ~510 ducks. Since then, the population has fluctuated between ~100 – 700 individuals due to winter storms, tsunamis, and outbreaks of avian botulism. In order to not have all of the Laysan duck eggs in one island basket, Laysan ducks were also reintroduced to Midway Atoll in 2005 and Kure Atoll in 2014.

Laysan is now part of the North-western Hawaiian Islands National Wildlife Refuge and was designated as a Research Natural Area by the US Fish & Wildlife Service in 1967. This means that the island is only open for scientific research and monitoring. While the population on Laysan island is currently relatively stable, scientists continue to monitor these ducks—a significant natural disaster, disease outbreak, or predator introduction could quickly disrupt this stability. Conservationists will likely step in with more intensive management if invasive mammals regain a foothold on the island, if the critical central lake is becoming filled with blowing sand, or if the critical vegetation on the island is damaged.

Social Life
The ~500 – 700 Laysan ducks on their small island home will congregate for activities such as drinking from freshwater seeps and courtship, and will disperse for activities such as feeding. These ducks pair-bond, but males do not take part in the rearing of offspring and are only together with their partner during courtship and after either brood rearing success or failure. Pairs were observed staying together about half the time from one nesting season to the next.

Habitat and Range
Laysan ducks were historically found along the entire Hawaiian archipelago, but their range was reduced to only the island of Laysan, which is a small island in the Hawaiian archipelago about 1000 miles northwest of Oahu. As part of conservation efforts, they have now been reintroduced to Midway Atoll in 2005 and Kure Atoll in 2014.

Laysan island is only about 1 mile (1.6 km) wide and 1.5 (2.9 km) miles long, and has a large central lake. There were historically sandalwood trees and fan palms on the island, but there are now no trees, only an introduced shrub and a mix of herbaceous plants. Laysan ducks utilize all of this habitat, moving between the lake and various vegetation areas depending on their food, water, and nesting needs.

Diet
Laysan ducks are dabbling ducks, largely feeding on invertebrates near the surface of Laysan lake, as well as aquatic plants and seeds. These ducks have also been observed running through large swarms of brine flies and grabbing the flies out of the air as they go.

Predators
The Laysan duck evolved around avian predators but did not evolve around ground-dwelling predators, evidenced by their tendency to freeze in place when threatened, which is effective when a threat is above, but less so when a threat is right next to them. Currently, larger seabirds such as frigatebirds may prey upon eggs and ducklings, but an adult Laysan duck has no natural predators.

Reproduction
Sexual Maturity:  ~1 year
Nesting Season: mostly April – August, occasionally February – November
Incubation: ~28 days
Clutch Size: usually 4 eggs

Adult Laysan Duck by Mark Pressler