Pacific Island Ecosystems Research Center
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 Male Laysan Duck. (Photo by Evan Jorgenson, USFWS volunteer) Background Island ecosystems throughout the Pacific have undergone catastrophic species loss, largely due to the effects of alien or non-native species. Rats, in particular, pose significant threats to native species. In Hawai‘i, the appearance of rats (which are not native to Hawai‘i) in the subfossil record coincides with the disappearance of ground nesting birds. Sadly, only three of Hawai‘i’s 10 endemic waterfowl species still exist today. The Laysan Duck (Anas laysanensis), also known as the Laysan Teal, is a critically endangered dabbling duck that is restricted to a single population on the remote and rat-free Laysan Island (Fig. 1). The Laysan Duck was listed as an endangered species in 1966 because of its small population, limited distribution, and dependence on a fragile island ecosystem. The same threats identified in 1966 continue to plague the species today. Justification The Laysan Duck was believed to be endemic to Laysan Island until 1995, when subfossil remains of the species were found on Hawai‘i, Maui, Moloka‘i, O‘ahu, Kaua‘i, and Lisianski islands. Discovery of Laysan Duck bones on these islands provided justification for re-introduction of the species to portions of its assumed former range. Although the Laysan Duck can fly, its reduced power of flight and other adaptations prevent it from dispersing from Laysan Island. Conservation strategies based solely on protecting Laysan Island are risky, as natural events such as drought, |
Hurricanes, and tsunamis have the potential to eliminate the
species. Disease outbreaks and predator introductions are also
serious threats. Creation of at least one other wild population is
a high priority in the Laysan Duck Recovery Plan. Selecting and Preparing a Release Site Nine potential sites in the Hawaiian Islands were considered for Laysan Duck release. A diverse team of scientists and land managers ranked the sites by evaluating 12 variables for each site, including: extinction risk, habitat quality, and predator absence. In 2003, Midway Atoll National Wildlife Refuge (Midway Atoll NWR) was chosen by the Laysan Duck Recovery Implementation Committee as the most suitable site for the experimental translocation, largely due its “rat-free” status and the logistic feasibility of restoring habitat and monitoring the ducks after release (Fig. 2). Once the site was selected, USGS and USFWS collaborated on restoration of Midway Atoll NWR to benefit the Laysan Duck and migratory waterbirds. Efforts to enhance and create wetlands and restore native vegetation began long before the arrival of the Laysan Duck. In addition, volunteers removed weeds, and planted native bunch grasses to provide cover and nesting habitat for the ducks. 
Figure 1. Laysan Island is
approximately 1500 km
(~ 930 mi) northwest of
Honolulu and is protected
as part of the Hawaiian
Islands National Wildlife
Refuge. USGS has been
conducting ecological
studies on the endangered
Laysan Duck here
since 1998.
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| U.S. Department of the Interior USGS FS 2005-3128 | U.S. Geological Survey November 2005 | |
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Selecting Ducks for Translocation Population Monitoring Before removing ducks from Laysan, it was important to understand their population dynamics so as not to endan- ger the only source population. Laysan Ducks reached the brink of extinction in the early 1900s due to the devastating ef- fects of introduced rabbits on the island’s vegetation. Once rabbits were eradicated from the island, the duck population be- gan to recover. However, the population has gone through other severe popula- tion bottlenecks. In 1993, the population crashed during El Niño drought condi- tions, which reduced food availability on the island. Since 1991, Laysan Duck populations have been monitored with 
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regular surveys. Earlier bird counts were
used to make rough population estimates
going back to 1961 (Fig. 3).
In 2004, there were approximately 576
ducks on Laysan Island.
Breeding
Reproductive success of Laysan
Ducks on Laysan Island has been moni-
tored since 1998. Adult birds were cap-
tured and given unique leg bands or radio
transmitters to identify individuals and
allow observers to follow their survival
and reproduction. Weekly surveys were
conducted to estimate the population size.
On Laysan Island, 30% of ducklings typi-
cally survive to fledge (Fig. 4). Of 170
ducklings hatched in 2004, 54 fledged
successfully, a number sufficient for
removing ducks for translocation Figure 3. Laysan Duck population estimates for years with available data. (USFWS/USGS data) |
 Figure 4. Reproductive success for Laysan Ducks on Laysan Island. Broods are families; ducklings are too young to fly; and fledglings are independent juveniles that have grown flight feathers. 1998 and 2002 were poor reproductive years, but 2004 breeding success was sufficient for the translocation of fledglings. (USFWS/USGS data) Candidate selection on Laysan Scientific studies and models showed that removing juvenile birds, as opposed to adults, was likely to have a negligible impact on the duck population on Laysan Island. In 2004, USGS collaborated with USFWS on translocation of the endangered Laysan Duck from Laysan Island to Midway Atoll NWR to establish a second wild population. Broods were checked daily during the breeding season (April–July) using spotting scopes to determine familial identities and survivorship. Thirty juvenile ducks from different families were fitted with radio transmitters. On the night of capture for translocation, the 20 best candidates (based on brood identification, body condition, and examination by USGS veterinarian) from the 30 radio-tagged individuals were then targeted for capture and translocation. Translocation and Release In October of 2004, the 20 ducks selected for translocation made an arduous two day voyage by ship to Midway Atoll NWR. All survived the journey. Upon arrival, the ducks were held in aviaries from 2–14 days to become accustomed to local food items, including invertebrates. Ducks were released in small groups. All were radio-tracked so that their movements, behavior, and survival could be closely monitored post-release. Supplemental food was offered several times per week for the first two months. To date, there has only been a single mortality; |
in December 2004, a male duck died after being bitten on the
head by a Laysan Albatross.
Translocated Ducks Breed on Midway
On Laysan Island, ducks do not typically breed until they are
two years old and breeding was not expected at Midway Atoll
NWR until 2006. So, biologists at Midway have been encouraged to observe that the translocated ducks are already breeding
successfully. To date, nine nests have been discovered and at
least 10 ducklings have fledged.
Implications for the Future
This work has contributed to the development of methods for
the safe and effective translocation and release of an endangered
duck in Hawai‘i. This has been an enormous first step in the
recovery of a critically endangered species, and it promises to Above. Radio transmitters were attached to the ducks prior to their release at Midway Atoll NWR so that their behavior and survival could be monitored. USGS biologist M. Vekasy attaches a radio while USFWS biologist J. Klavitter holds bird. (Photo by Michelle Reynolds, USGS) generate valuable knowledge of the Laysan Duck that will be applied in future translocations of the species. Knowledge of Laysan Ducks to date comes from Laysan Island, a harsh and unique environment when compared with the range of habitats this species occupied in prehistory. Translocation to Midway Atoll NWR provides scientists with an opportunity to evaluate the ability of the Laysan Duck to adapt to portions of its presumed prehistoric range, on an island lacking the extensive hyper-saline ecosystem of Laysan Island. |
Non-sibling juvenile
ducks were selected for translocation
to maximize genetic
variability of the
Midway population.  (Photo by Michelle Reynolds, USGS) |
Juvenile Laysan Ducks were
released in small groups at
freshwater seeps on Sand
Island, Midway Atoll NWR
after a brief holding period in
the aviaries. USGS biologistL. Laniawe releases a bird.  (Photo by John Klavitter,USFWS) |
 Laysan Duck nest on Sand Island, Midway Atoll NWR (Photo by John Klavitter, USFWS) Monitoring the translocated Laysan Ducks at Midway Atoll NWR will significantly increase our knowledge of the species’ flexibility in life history traits and resource requirements. In particular, it will be useful to study the demography of a new, growing population as it becomes self-sustaining in an environment different from Laysan Island. It is the hope of USGS scientists that this preliminary work will make an enormous contribution to the recovery and conservation of the species. Recommended Reading on the Laysan Duck: Prehistoric Distribution Burney, D.A. et al. 2001. Ecological Monographs 7 1(4):615-642. Cooper, A. et al. 1996. Nature 381:484. Olson, S.L. & A.C. Ziegler. 1995. Pacifi c Science 49(2):111–125. Biology/Ecology Reynolds, M.H. 2004. Waterbirds 27(2):183–192 Reynolds, M.H. 2002. PhD Dissertation, Department of Biology, Virginia Polytechnic and State University, Blacksburg, VA. Reynolds, M.H. & T.M. Work. 2005. Wildfowl 53. Work, T.M. 2004. Journal of Wildlife Diseases 40(1):110–114. Endangered Species Recovery Plan US Fish & Wildlife Service website: www.fws.gov/endangered/recovery/ | 
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| U.S. Department of the Interior USGS FS 2005-3128 | U.S. Geological Survey November 2005 | |
U.S. Department of the Interior |
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