(DRAFT) - Taxonomy
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
TAXONOMY
NAME - DUCK, LAYSAN
OTHER COMMON NAMES - DUCK, LAYSAN; TEAL and LAYSAN
ELEMENT CODE -
CATEGORY - Birds
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - AVES,
ORDER AND SUBORDER - ANSERIFORMES,
FAMILY AND SUBFAMILY - ANATIDAE,
GENUS AND SUBGENUS - ANAS,
SPECIES AND SSP - LAYSANENSIS,
SCIENTIFIC NAME - ANAS LAYSANENSIS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Laysan Duck
Anas laysanensis Rothschild, 1892
KINGDOM: Animal GROUP: Bird
PHYLUM: Chordata CLASS: Aves
ORDER: Anseriformes FAMILY: Anatidae
The Laysan duck clearly originated from the mallard (Anas
platyrhynchos) stock isolated on this remote Hawaiian Island. Like
the mallard, it has a purple wing speculum, and many males have the
curled upper tail coverts. Like most endemic island ducks, it is
teal-sized, dull-colored, and with small extremities (18). Unlike the
mallard, sexual dimorphism in color is much less prominent, but males
can be identified by a greener head and plain yellow rather than
spotted orange bill. Mean weights recorded during summer varied from
403 g to 556 g, with laying females being the heaviest during spring;
male weights generally exceeded female weights later in the summer
(10).
The species was discovered before 1826 (16); type specimens were
collected in 1891, and the species was formally described in 1892 (12)
as Anas laysanensis. Delacour & Mayr (05) recognized its mallard
origin and considered it a subspecies of the mallard to demonstrate
Taxonomy - 1 (DRAFT) - Taxonomy
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
this ancestry, Anas platyrhynchos laysanensis. The A.O.U. Check-list
(01) now gives it full species status, Anas laysanensis. Another
common name for the Laysan duck is the Laysan teal (15).
Fifty-three specimens were known to be in museums in the early
1970's (07), and about 333 were known in zoos in 1975 (15). In
addition to the description by Rothschild (12), detailed
characteristics were outlined by Phillips (11), Delacour (04), and
Berger (02).
Taxonomy - 2 (DRAFT) - Status
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
Federal Migratory
Commercial/consumption
Ornamental
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Laysan duck (Anas laysanensis) has been designated an
Endangered species pursuant to the Endangered Species Act of 1973 (50
CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C. 1531-1540), as
amended. The species has this status wherever found including the
State of Hawaii.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
The species is protected by the Migratory Bird Treaty Act
(16 U.S.C. 703-711 et seq.) (50 CFR 10.13).
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
Status - 1 (DRAFT) - Status
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
STATE: Hawai'i
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Department of Land and Natural Resources,
Divison of Forestry and Wildlife.
STATE STATUTE: Hawai'i Revised Statutes, Chapter 195D;
Admin. Rules of HI, Sec. 13-124-2 and 13-124-3.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The Laysan duck is listed in Appendix I of CITES. It is also
listed as Rare in the IUCN Red List of Threatened Animals (1986), and
is listed by the U.S.in the Annex to the Convention on Nature
Protection and Wildlife Preservation in the Western Hemisphere (1970).
ECONOMIC STATUSES:
The species currently is of minimal economic importance, at most
as an ornamental species bred by aviculturalists. Historically,
however, guano miners (1891-1903) and Japanese plume hunters
(1908-1910) shot numerous birds for food (07).
67/03/11:32 FR 04001/ - Original listing
70/08/25:35 FR 13519/13520 - Proposed relisting
70/10/13:35 FR 16047/16048 - Final rule on previous list
76/05/05:41 FR 18618/18624 - Proposed rules for captive breeding
77/02/22:42 FR 10465/10488 - Ruling on CITES with listing
77/06/01:42 FR 28052/28057 - lists of captive stock
79/05/21:44 FR 29566/29577 - Status review
79/09/17:44 FR 54002/54008 - Captive propagation/export of Laysan duck
85/07/22:50 FR 29901/29909 - Five year review
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
TERRESTRIAL
TERRESTRIAL
INLAND AQUATIC
COASTAL
LAND USE -
Herbaceous Rangeland
Lakes
Bays and Estuaries
Nonforested Wetland
Beaches
Sandy Areas other than Beaches
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Lacustrine, littoral OW0
Lacustrine, littoral FL4
Lacustrine, littoral FL3
2FL
Lacustrine, littoral EM3
Palustrine OW0
Palustrine FL4
Palustrine FL3
Palustrine FL2
Palustrine EM3
Marine, intertidal RS1
Marine, intertidal FL3
Marine, intertidal FL
Marine, intertidal BB2
Marine, intertidal BB
COMMENTS ON HABITAT ASSOCIATIONS -
Although unusual by continental standards, the Laysan duck
resembles other insular waterfowl in being highly terrestrial as well
as aquatic, and by utilizing the entire range of habitats available on
Laysan Island (18). Habitats utilized include the higher sparsely
vegetated sand dunes, more protected shrubs in the interior of the
Island, water tolerant vegetation like Cyperus laevigatus that rings
the lake, mud and sand flats around the lake, and the central
hypersaline lake, including shallow open water (07,10). Most
observers agree that the central hypersaline lake is the focal point
of the population where it feeds and loafs in the cooler parts of the
day and at night (07,10,13). The availability of fresh water seeps
are a major attraction as well. At one time ponds of freshwater were
more common than they are now, and were favored habitats of the ducks
(17).
Ducks sometimes use ocean shallows for bathing (17), possibly
because this water is fresher than the lake, and they use the beaches
for loafing and preening after bathing (10). They do not swim far
from shore or battle waves along the shore, but rather seek out very
protected areas. Occasionally they use tidal pools for bathing and
resting (13,17), and more rarely feeding, but this is not common on
Laysan. In the uplands, they are commonly seen loafing during the day
under the shade of the beach morning glory (Ipomea pes-caprae), and
taller shrubby vegetation such as Scaevola taccada. They nest mostly
Habitat Associations - 1 in the taller vegetation such as Eragrostis variabilis (10), Cyperus
(17), Heliotropium (10), beach morning glory (13), but also under
shrubs like Chenopodium (08) and Scaevola (17). When light
intensities are low they wander in open areas, such as Sesuvium
covered mud flats, with relatively little fear of man or of birds
flying overhead.
Some workers consider the presence and level of the lake to be
directly related to the success of the species. This may well reflect
both fresh water supply and diversity of feeding opportunities for
young.
Habitat Associations - 2 (DRAFT) - Food Habits
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
LIFESTAGE FOOD FOOD PART
General Crustaceans
General Arthropods
Food Habits - 1 (DRAFT) - Environment Associations
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Aquatic Features: Springs [flowing]
G Coastal Wetlands: Mangrove swamps
G Coastal Features: Reefs
G Coastal Features: Sandy offshore islands
G Coastal Features: Vegetated offshore islands
G
Environment Associations - 1 (DRAFT) - Life History
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Food habits of Laysan ducks are poorly known. Early collectors
did not always record or at least publish such data and few specimens
have been collected recently. The species is highly carnivorous
during much of the year. Most workers have been present during the
summer and noted the dependence of the adults and ducklings on
brineflies (Neoscatella sexmaculata) (08,10,17) on the mud-flats
around the lake, which are obtained by chasing and grabbing. They
also dig under and in seabird carcasses for fly and beetle larvae.
Brine shrimp (Artemia sp.) are present in large quantities in the lake
during spring and early summer, and ducks do dabble and even up-end
for food where they might get shrimp or fly larvae (15). Several
workers have seen the bird feed in the tidal rocky areas on the south
part of Laysan Island but regarded this as an incidental source of
food (13,17). All ages also wander in the uplands at night searching
for larvae of cutworm moths (Agrotis dislocata) that are very abundant
in the sand (10,17). Butler & Usinger (03) collected ducks with
Agrotis larvae in the tracts. There are no submergent plants or
filamentous algae in the lake suitable for food (17). The use of
seeds or fruit has not been established.
HOME RANGE/TERRITORY:
Observations based on banded and even color-marked ducks
suggested that individuals and pairs tended to occupy the same ranges
(17). This was the basis for Warner's grid census system (17). More
recent studies using radio transmitters support this general concept
but show that birds are highly mobile, utilize generally the same
areas within a given season, but occasionally wander off significant
distances (10). Pairs remain together in the same area for several
weeks or more during pre-nesting, but segregate after incubation and
brood rearing starts (10).
PERIODICITY:
Laysan ducks are rarely active during the heat of the day, unless
disturbed from their shaded rest areas in shrubs and grasses. They
seem more active on overcast days, but quantitative data are lacking.
Based on time-lapse film records, the ducks become active in the
evening, with a peak shortly after dark, and a second and often larger
peak of activity near sunrise (10). Although other ducks also are
known to be active at night, no other species is known to be so
inactive during the day (10).
MIGRATION PATTERNS:
The species is non-migratory and has not been recorded on other
islands in the area (15).
COVER/SHELTER REQUIREMENTS:
Because of the habitat breadth of island endemics, and the
observed use of virtually all cover types by Laysan ducks, Laysan
Island must be maintained in its present state if the species is to
survive. Few species of plants remained during the peak populations
Life History - 1 (DRAFT) - Life History
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
of rabbits, which was correlated with the smallest known number of
surviving ducks (07,17). However, the same plant species composition
seems to have returned (07). Cover is essential for nesting, both for
shade of the females and the eggs, and to reduce any potential egg
predation from aerial egg predators or perhaps Laysan finches.
REPRODUCTIVE SITE REQUIREMENTS:
Display has not been studied intensively and probably is not
conspicuous because of the continuing social interactions of members
of as small population. Displays have been photographed in captivity
by Johnsgard (09) and filmed in the wild by Moulton (10), and are
similar to those of the mallard. They occur mostly on the water at
the edge of the lake (10).
As with most ducks, nests are built with on-site materials, in a
shallow bowl surrounded by and usually under a vegetative canopy (17).
The female adds modest amounts of down to the bowl in early incubation
(10). Nests have been recorded in Eragrostis (10), Scaevola and
Cyperus (17), Chenopodium (08), Heliotropium (10), and Ipomea (13).
All sites have been well above water levels and no nest flooding has
been recorded.
REPRODUCTIVE CHARACTERISTICS:
Age of sexual maturity is unknown but presumably occurs at
one-year. Monogamy is the norm and pair bonds may be longer lasting
than in continental ducks because they are non-migratory, but mates
are commonly switched between breeding seasons (10). Rape has been
recorded several times at a population high (10). The nesting season
is long but also variable, due probably to water conditions. A single
Spring-early Summer breeding period is normal, extending from March to
June, or April to July (10). Clutches are small, ranging from 3 to 6
(07,08,10,17). Incubation period is reported to be 26 days,
presumably based on captive birds (14). Brood sizes range from 1 to 8
(10), but fusion of broods of several ages is not uncommon.
PARENTAL CARE:
Only the female incubates the eggs and cares for the young,
although males occasionally stay nearby. The young are precocial but
brooding is important for the first two weeks of life, due to
mortality in driving rainstorms (10). Broods are cared for until they
are at least partly feathered, but mixing of several broods of
different ages is not uncommon (10).
POPULATION BIOLOGY:
Although the accuracy of population estimates probably is low,
the species was certainly near extinction following the devastation of
the vegetation in the early 1900's. At that time estimates indicated
less than 20 birds existed (07,17). The comeback of the population
with protection followed a typical sigmoid curve, to a level estimated
at 740 in 1961 (17). More recent work with most of the population
banded suggests populations of 476 to 489 in 1980, which probably is a
more realistic figure (10). Reproductive rates are obviously low with
relatively few of the females successfully rearing broods (10). An
estimated recruitment of only 6.3% occurred between 1979 and 1980.
Life History - 2 (DRAFT) - Life History
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
Several 12-year-old banded birds were found in 1979, suggesting that
this species is much longer lived on this isolated island than is
characteristic of continental species (10). There is sufficient
evidence of social stress at a population level of 500 that this
probably represents the present carrying capacity of the Island. This
level would be difficult to exceed through management. It would be
more important to the species to insure that no reductions in
vegetative cover occurs through introduced herbivores or plant
disease, that the central lake remains at its present size, and that
no predators are introduced.
SPECIES INTERRELATIONSHIPS:
Interspecific relationships of this species with other species
are difficult to document. The Laysan finch (Telespyza cantans) has
been observed eating abandoned duck eggs, but whether they eat eggs in
active nests isn't known (10,17). One record of a Laysan duck being
killed by a collision with a large seabird may be quite rare (10).
Great frigatebirds (Fregata minor) have been seen to harass ducklings
but no kills have been noted (06). Several species of migrant ducks
have been recorded on the lake (07,17), but do not seem to mix with
Laysan ducks.
OTHER LIFE HISTORY DESCRIPTORS:
None.
Life History - 3 (DRAFT) - Management Practices
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Controlling/Restricting Boating Activities
Beneficial Restricting/regulating human disturbance of populations
Beneficial Developing/maintaining/protecting wetlands
Beneficial Reforestation
Beneficial Controlling/Removing Nonnative Vegetation
Beneficial Stocking captive-reared wild-strain animals
Beneficial Disease Control Measures
Beneficial Controlling/Removing Exotic Vertebrates
Adverse Subsistence Hunting/Fishing/Trapping
Existing Subsistence Hunting/Fishing/Trapping
Adverse Exotic/Feral/Introducted Species
Existing Exotic/Feral/Introducted Species
Adverse Grazing
Existing Grazing
Adverse Vegetation Composition Changes
Existing Vegetation Composition Changes
COMMENTS ON MANAGEMENT PRACTICES -
Populations of the Laysan duck inherently are limited by the size
of Laysan Island, probably by variations in food supplies, and by the
lack of nearby islands with suitable habitat for expansion during
population highs. Because they are highly terrestrial and often
nocturnal (10,17), censusing is difficult, and population estimates
probably have low reliability. Nevertheless, counts have been as low
as 12 and estimates as high as 740 (07), but the current (1984)
population of 480-500 is the most reliable yet obtained because nearly
all the birds were banded (10).
Human-induced influences have been the most detrimental to the
species. Guano miners (1891-1903) and Japanese plume hunters
(1908-1910) shot numerous birds for food (07), but their impacts were
not measured. It was the introduction of domestic rabbits and guinea
pigs as a commercial venture that stripped the Island of vegetation
and resulted in the lowest population recorded, about 12 (02,07,15).
In 1923, a biological survey expedition shot out the entire population
of rabbits, and the 14 remaining ducks (20 ducks were counted at that
time and 6 were collected) are presumed to have been the basis of the
current population (07).
There are no known predators on Laysan Island although great
frigatebirds (Fregata minor) that nest on the Island have been
considered potential predators on ducklings (06). There has been no
confirmation of this or of the significance of observations that the
omnivorous Laysan finch (Telespyza cantans) eats abandoned duck eggs
(10,17). After two summers of intensive study, the most serious
mortality recorded in ducklings was due to heavy rain storms, and some
mortality of hens was caused by intraspecific interactions, including
rape. Such influences may well be more prominent at population highs,
as occurred during this study (10).
The most serious threat to the Laysan duck is the potential of
Management Practices - 1 (DRAFT) - Management Practices
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
predator introduction. Rats (Rattus spp.) and mongooses (Herpestes
auropuntatus) both have impacted waterfowl on other tropical islands,
including Hawai'i (18). A Japanese ship was wrecked on the island in
1970 but rats either were not on the ship or perished (15). Periodic
monitoring of duck populations and predator sign is essential.
The second major threat is that of sand blows which have covered
grassy vegetation on the east side and even reached the central lake
(07,10). The Island is at most only 40 feet high. In severe storms,
there is a possibility that sand could significantly reduce the size
of the lake, on which the ducks depend for food throughout much of the
summer. Control of sand blowouts may be essential, since the impact
would be not only on the lake, but could eliminate upland nesting
vegetation as well.
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1982. The Laysan Duck Recovery Plan.
U.S. Fish and Wildlife Service, Portland, OR. 38 pp.
Being confined to the hypersaline lagoon at Laysan Is., the
Laysan duck's population will always be small and highly vulnerable to
disturbances brought to the Island by man's activities. Especially
feared are illegal, episodic hunting and the accidental introduction
of predators or other detrimental alien organisms. For these reasons,
the prime objective of the Laysan Duck Recovery Plan is "to perpetuate
the Laysan Duck on Laysan Island; to protect the natural island
habitat; and to down-list the species from Endangered to Threatened."
The plan calls for the following recovery actions:
1. Continuing management of the duck and its habitat under
regulations of the refuge and Research Natural Area, especially
keeping people and ships away from the island.
2. Annual population monitoring.
3. Continuing ecological studies of Laysan.
4. Implementing a plan to detect and eradicate exotic organisms
(mammals, plants, disease causing organisms, etc.) introduced in the
future. A handbook is needed to assist refuge managers in
distinguishing between native and alien plants.
5. Ongoing captive propagation.
6. Public education.
Since publication of the recovery plan, recovery actions for the
Laysan duck have advanced on all fronts. The USFWS refuge office has
developed contingency plans to detect and eradicate mammals, should
they be introduced in the future. Likewise, there are now contingency
plans for oil spills and avian diseases. Population surveys are
conducted at least annually by the same office; surveys have been
standardized and redesigned to be more readily interpreted. To
Management Practices - 2 (DRAFT) - Management Practices
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
prevent the introduction of alien plants and animals, a protocol has
been established for all persons visiting Laysan. Surveys are
conducted to detect alien species on the island. Monitoring of the
habitat (under #1 above) identified an unaccounted for and complete
loss of vegetation on the dunes bordering the island's hypersaline
lake. The loss of vegetation caused a shifting of the dunes which
threatened to fill the center of lake and the freshwater seeps used by
the duck. Drift fences were installed and the potential need to
revegetate the dunes was identified, however, natural revegetation
appears to be occurring. The USFWS supports research on the Laysan
duck by providing permits, general guidance, and logistical aid.
Captive flocks have been established in a number of zoological parks
and government breeding facilities in Hawai'i, on the mainland U.S.
and in foreign countries. No action has been taken as of 1986 on a
floral handbook.
Management Practices - 3 (DRAFT) - References
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 American Ornithologist's Union. 1983. Check-list of North
American birds, 6th ed. Allen Press, Lawrence, KS. 877 pp.
02 Berger, A.H. 1972. Hawaiian birdlife. Univ. of Hawaii Press,
Honolulu. 270 pp.
03 Butler, G.D., Jr. and R.L. Usinger. 1963. Insects and other
invertebrates from Laysan Island. Atoll Res. Bull. 98:1-30.
04 Delacour, J. 1956. The waterfowl of the world, Vol.2. Country
Life, Ltd., London. 232 pp.
05 Delacour, J. and E. Mayr. 1945. The family Anatidae. Wilson
Bull. 37:1-55.
06 Dill, H.R. and W.A. Bryan. 1912. Report of an expedition to
Laysan Island in 1911. U.S. Dept. Agric. Biol. Surv. Bull. 42.
30 pp.
07 Ely, C.A. and R.B. Clapp. 1973. The natural history of Laysan
Island, northwestern Hawaiian islands. Atoll Res. Bull. 171.
361 pp.
08 Fisher, W.K. 1903. Birds of Laysan and the Leeward Islands,
Hawaiian Group. U.S. Fish. Comm. Bull. 23(3):767-807.
09 Johnsgard, P. 1965. Handbook of waterfowl behavior. Cornell
Univ. Press, Ithaca, NY. 378 pp.
10 Moulton, D.W. and M.W. Weller. 1984. Biology and conservation of
the Laysan duck (Anas laysanensis). Condor 85:105-117.
11 Phillips, J.C. 1923. A natural history of the ducks, Vol.2.
Longman-Green, London.
12 Rothschild, W. 1892. (Description of Anas laysanensis). Bull.
Br. Ornithol. Club. 1:17.
13 Sincock, J.L. and E. Kridler. 1977. The extinct and endangered
endemic birds of the northwestern Hawaiian Islands. Manus. on file
in U.S. Fish & Wildlife Serv., Honolulu, HI.
14 Todd, F.S. 1979. Waterfowl. Sea World Press, San Diego, CA.
399 pp.
15 U.S. Fish and Wildlife Service. 1982. The Laysan Duck Recovery
Plan. U.S. Fish and Wildlife Service, Portland, OR. 38 pp.
16 von Kittlitz, R.H. 1834. Nachricht von den Bruteplatzen einiger
tropischen Seevogle im stillen Ocean. Mus. Senckenb. 1:115-126.
17 Warner, R.E. 1963. Recent history and ecology of the Laysan duck.
Condor 65:3-23.
18 Weller, M.W. 1980. The island waterfowl. Iowa State Press, Ames.
121 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Clapp, R.B. and W.O. Wirtz. 1975. Natural history of Lisianski
Island, northwestern Hawaiian Islands. Atoll Res. Bull. 186.
02 Ely, C.A. and R.B. Clapp. 1973. The natural history of Laysan
Island, northwestern Hawaiian Islands. Atoll Res. Bull. 171.
03 Rothschild, W. 1900. The avifauna of Laysan and the neighboring
islands. R.H. Porter, London.
References - 1 (DRAFT) - References
Species DUCK, LAYSAN
Species Id ESIS101009
Date 14 MAR 96
04 Sincock, J.L. and E. Kridler. 1977. The extinct and endangered
endemic birds of the northwestern Hawaiian Islands. Manus. on
file: U.S. Fish & Wildl. Serv., Honolulu, HI.
05 von Kittlitz, R.H. 1834. Nachricht von den Bruteplatzen einiger
tropischen Seevogle im stillen Ocean. Mus. Senckenb. 1:115-126.
06 Warner, R.E. 1963. Recent history and ecology of the Laysan duck.
Condor 65:3-23.
References - 2