BEST MANAGEMENT PRACTICES FOR USE OF DUCKS AS APPLE SNAIL CONTROL
IN LO`I KALO.
On January 25, 2005 a meeting was held with taro farmers, duck breeders, snail specialists, avian biologists, Division of Forestry and Wildlife and U.S. Fish and Wildlife Service representatives in order to share information; to try and answer questions regarding native/domestic duck issues and policies in Hawai`i; and, to create opportunity for support in development of a duck management protocol that would benefit both taro farmers and the endemic koloa (Anas wyvilliana).
Both DOFAW and USFWS representatives showed unprecedented willingness to help taro farmers struggling with the apple snail problem. One result of that meeting was an agreement that taro farmers would work with the agencies to develop a "best management practices" document for use of domestic ducks as apple snail control in the state. That draft will be sent to state/federal agencies for review and comment by the end of October. The final document will become part of a statewide strategic plan for apple snail control currently being developed with extensive input from taro farmers across the state (expected completion December 2005). The present draft protocol has been developed through discussion and review with current users of ducks in taro farming communities on Kaua`i, Maui and Hawai`i.
Koloa (Anas wyvilliana) is Hawaii's only endemic (native) duck and is federally listed as endangered. Several factors contribute to this endangered status including the loss of wetland habitat and historic food resources, the presence of Mallards and other wild ducks which migrate from the mainland and interbreed with koloa; the release or escape of domestic ducks into the wild which then establish feral populations that cross-breed with koloa; and overall small numbers of pure koloa (an estimated 2,200 remain).
The largest koloa population is found on Kaua`i (about 2,000 birds), primarily in what is now the Hanalei Refuge, which was and still is one of the largest wetland taro growing regions in Hawaii's history. A small re-introduced population of koloa is also located on the island of Hawai`i. Feral mallard and koloa x mallard populations have now been recorded where only pure koloa were thought to have existed in Kaua`i. Past re-introduction efforts on O`ahu and Maui failed to eradicate existing feral mallard and hybrid populations as a precursor to recovery efforts; those populations are severely hybrizided (Engilis, Uyehara, and Giffin. 2002). Moloka`i duck populations are also feral and/or hybrid.
Kalo (taro) is the most culturally significant agricultural crop in Hawai`i. Historically, thousands of acres were cultivated; today, less than 500 acres of kalo lands are actively maintained. It is a primary and secondary income source and forms a significant portion of food budgets for taro-farming families (Levin et al, at press). Kalo is recognized as elder brother to the Hawaiian people and plays an important role in cultural identity, spiritual wellbeing, and the lifestyle of those who choose to plant it.
The apple snail Pomacea canaliculata, a highly aggressive invasive species, has become a serious threat to the survival of taro production. This particular species is present on all main islands except Moloka`i, Ni`ihau, and Kaho`olawe. It thrives best in perennial wetland areas which coincide with the largest taro producing areas in the islands. Crop loss from apple snails has been estimated at 18-25% (HAS 2004; Levin et al. in publication). Snails are also a vector for disease transmission to humans, including rat lung worm. The most frequently used control method is removal of snails and eggs by hand, an intensive and expensive process. Domestic ducks are currently the most effective and efficient method for apple snail control in lo`i kalo (wetland taro systems).
The US Fish and Wildlife Service and the Hawai`i Department of Land and Natural Resources Division of Forestry and Wildlife recognize that mallard and hybrid duck populations remain the single largest obstacle to restoring and protecting pure koloa in the wild on all islands in the state. Without implementation of a comprehensive mallard and hybrid eradication program by state and federal agencies, protection efforts for the koloa are moot.
The lack of consistent management of natural wetlands for much of the last century has left little suitable habitat for Hawaii's endangered waterbirds, except lo`i kalo. There are few enough viable taro lands remaining in the state, and growing kalo is back-breaking work with few financial rewards, even without the added constraints of an endangered species to deal with. While taro farmers support efforts to help the koloa, they also strongly recommend that in conjunction with feral duck control, state and federal agencies focus on restoring currently degraded wetlands outside of traditional taro-growing lands as the primary habitat for koloa and other native waterbirds, particularly in Hanalei, Ke`anae and Waipi`o. Lo`i kalo should be considered only as a temporary shelter and not earmarked as a permanent locale for these species. This will provide more suitable habitat and reduce potential conflicts between the survival of an ancient Hawaiian practice, farmers' livelihoods, and the protection of an endangered species.
Because the domestic ducks used to control apple snails are such a scarce and valuable resource, taro farmers carefully manage their ducks while in the lo`i and pen them nightly, most particularly to protect them from dogs, mongoose and theft. This limits opportunity for koloa - domestic duck interactions on farm and negates the opportunity for pair-bonding.
Both taro farmers and agencies acknowledge that the current source of feral mallards in the islands is not taro farmers' ducks, however, koloa, as with other native freshwater birds in Hawai`i, sometimes choose lo`i kalo as feeding, loafing, breeding or nesting habitat. The potential for cross-breeding between koloa and the domestic ducks used by taro farmers for control of the apple snail, although small due to the way farmers manage their ducks, does exist.
The purpose of this document is to provide taro farmers with the best protocols available for using ducks as a method of apple snail control in Hawai`i (based on local farmers experience) while protecting to the best degree possible, endemic populations of koloa from further hybridization due to new controlled domestic duck populations in taro farming areas.
Best duck selection and best management practices in each section are listed first (1) and/or bolded, followed by acceptable alternatives. The criteria for "best" included feasibility and accessibility for farmers, simplicity, and level of risk to koloa. In developing these practices, it is recognized that current duckling resources for taro farmers are extremely limited, as are farmer's financial resources. Where the best duck variety choices may not be possible, best management practices maintain a high level of prevention.
Engilis, A., Jr., Uyehara, K.J. & Giffin, J.G. 2002. Hawaiian Duck (Anas wyvilliana). In: The Birds of North America (eds. Poole, A. & Gill, F., eds.), No. 694. The Birds of North America, Inc., Philadelphia.
Engilis, A., Jr., and Uyehara, K.J. Genetics and Morphometrics of Koloa. presentation 2005 Wetland Mangement in the Hawaiian Islands Workshop: Connecting Research and Management. October 6-7, 2005. Kailua, Hawai`i.
HAS (Hawaii Agricultural Statistics) 2004. Hawaii Taro. February 9, 2004. Hawaii Agricultural Statistics , Honolulu. https://www.nass.usda.gov/hi/
Levin, Penny et al. 2005. Apple Snail Invasions and the Slow Road to Control: Ecological, Economic, Agricultural and Cultural Perspectives in Hawaii in press for a volume on apple snails to be published in the Philippines [title not yet confirmed].
I. Duck Characteristics
The following are the best characteristics for ducks working in lo`i kalo. The size, behavior, and disposition of the ducks will influence the quality of their work in controlling apple snails and limit the potential for hybridization with the endemic koloa.
1. Naturally flightless. Some duck breeds are naturally flightless, including the Roen, a cousin of the Mallard, but may not be suitable due to their higher potential for cross-breeding with koloa or skittish nature. Pekin are large-bodied, heavy birds, that do not fly and are preferred by taro farmers on the island of Hawai`i.
2. Pinioned ducks. A pinioned duck is one that is restrained from flight, either by clipping a wing (must be done after each molt) or removing the wing tip (permanent). See attachment for details on how to pinion. This option requires regular monitoring.
1. Females. Females are less aggressive, and more focused, steady snail eaters than males. Only a limited number of males are needed if fertile eggs are desired, however, during koloa breeding season both male and female domestic ducks should be well-managed.
a. Recent koloa genetics research from a limited sample size suggests that more hybrids may come from a cross between a female mallard and a male koloa (Engilis and Uyehara, 2005) than previously understood; while slightly earlier documentation suggests the reverse (Engilis, Uyehara, and Giffin. 2002).
b. Pairing in koloa can occur year-round; however, late fall and early winter are the primary seasons.
2. Sterile ducks. An option that resolves the reproductive and flight issues of using domestic ducks near koloa populations is sterile ducks. Mule ducks are available from at least one source in California (Metzer Farms) but would need to be brought in under a special HDOA permit. It is possible to set up a breeding program to develop mule birds in Hawai`i. This may be the most viable option for sites such as Hanalei.
a. A mule or Mullard is a cross between a Pekin female and a Muscovy male; a hinnie is the result of a Pekin male and Muscovy female. A mule is typically large, swims well but does not fly. Hinnie males fly. Approximately 60% of mules are male. Both mules and hinnies are sterile. A female hinnie can lay eggs but they do not hatch. It is however, difficult to breed Pekin and Muscovy and the resulting eggs have only a 20-30% fertility rate. These birds are raised on the mainland primarily for pate (liver). They have characteristically large, clawed feet like a Muscovy (potential to damage banks) and are untested for their behavior in taro lo`i (pers. com. John Metzer 2005).
3. A veterinarian can sex and sterilize ducklings, however, to our knowledge there is currently no one in the state of Hawai`i with this experience. Costs are unknown.
1. Start with ducklings. Young ducks will readily become familiar with a farmer, a routine, and the snails as a food source, as a form of imprinting/training. Adult birds will have difficulty bonding with a farm and new routine.
2. Well-mannered. Choose breeds that are mellow in nature, easy to herd, quick to get into the routine of snail feeding, and can be left to themselves once in the taro patch. Duck breeds that are easily spooked will require more attention and time to watch. Herd dogs may be an option which will also provide some protection from hunting dogs, however, that involves an additional commitment of time, training and feed/care costs.
D. Able Feeders
1. Age. Juvenile ducks will eat more snails than mature ducks. If your ducks survive dogs, mongoose and disease, they will live an average of 5-6 years and will need to be replaced. Introduce new ducklings into your existing flock rather than starting a new juvenile group; the adult birds will influence the behavior of the young ones.
2. Breed. Not all domestic ducks feed alike. Small beaked birds will be limited to consuming smaller-sized snails. Based on current farmer experience, Pekin and Black Cayuga appear to be the most capable snail feeders.
3. Timing. Ducks will feed, rest, play, and return to feeding in cycles during the day. You will observe this activity if you leave your ducks in the lo`i all day long. They may occasionally lose interest in feeding on snails and damage the taro plants, particularly when snail numbers are low. A better alternative is to release ducks to feed on snails a few hours at a time, once or twice per day, and return to the home pen to keep them focused on the snails (see III. B. below). This also reduces opportunities to wander.
a. The times you don't want ducks in your lo`i are when taro plants are older and apple snail populations are low, and/or when pocket rot is prevelent. The ducks will dig into the taro plants in search of food and undermine them. Too many ducks in one patch will result in the same type of behavior.
1. Most recommended. Pekin appears to be the best breed due to its larger size (koloa are small birds), visibility (they are all white), lack of desire or ability to fly, large appetite for snails and easy nature. Black Cayuga's are good snailers but are more closely related to Mallards.
2. Not recommended. Mallards and other closely related species, such as Rouen, Cayuga, Khaki Campbell, and Indian Runners (all of which look similar to mallards), have the highest potential for hybridization with koloa.
3. Muscovy are not Mallards but are harder to control and, along with Indian Runners, are known to tear up the banks of the lo`i and dig around the base of the kalo more than other breeds. They also fly.
4. Working with what you have. Pekin ducklings and adult birds are scarce in the present market on all islands. If all you have are lesser preferred breeds, use the practices described in this document to keep your ducks safe and out of koloa areas.
II. Penning and caging
Penning and caging will serve several purposes, including to protect your ducks from dogs and mongoose, to prevent cross-breeding with koloa, to control breeding within your own stock, and to keep capture and herding simple.
A. 'Home-base' Pens or Cages
1. Weeks one through four. Ducklings require frequent attention during the first three to four weeks and should be kept in a sheltered, warm, small cage or box away from dogs, mongoose, rain, wind, and dirty water to improve survival rates. Duckling feed during this time is typically "chick starter".
2. Juveniles and Adult Pens. There are many options. The simplest, least costly designs are described below.
a. Brood shelter with protective fence. A cage of wire and plywood (approx 4x6ft) about three feet off the ground on 2x4in legs with a plywood roof and strong wire flooring makes a good brooding and shelter house. This keeps them dry and out of the rain. Holds up to 10 ducks if they are let out often.
A dog proof fence of heavy wire around this structure is strongly recommended. Both can be light weight enough to move around. Ducks will walk down a ramp into a cage or trailer to be moved. A true mongoose-proof fence is extremely expensive; setting out traps may be more cost effective and reduces overall numbers of this pest for your ducks and koloa.
b. Over an `auwai or lo`i edge. A wire and plywood cage built on the ground, half over the `auwai and half on solid ground works well for farmers who are not able to be on-farm daily. The ducks will always have clean water and some food from the `auwai. Solid lower walls will protect the ducks from dogs and also keep them calm when penned. Very strong wire needs to be used to dog-proof the cage. Place cobbles along the `auwai edge to protect the banks from eroding. Maximum 6 ducks.
c. For more than 6 ducks. A four to six foot high chain link pen about 15ft in diameter with water piped into a small pond in the center and piped out to a lo`i (natural fertilizer) is a more natural environment for ducks that are not worked daily. A cage fits inside for ducks that need shelter or to grow out ducklings. Mongoose-proof the lower edge if you plan to collect eggs. From 15 to 20 ducks.
B. In the lo`i
1. Lo`i perimeter. Flexible plastic fencing may help keep your ducks in the proper lo`i as they begin to learn the system of feeding and returning to their pen. Once the pattern is established such fencing is not usually necessary.
2. Farm perimeter. Stray dogs are the number one source of duck loss for taro farmers. They can indiscriminately kill a whole flock in very short time. You may need to hogwire the perimeter of your farm to keep stray dogs out.
These options are expensive and an additional aggravation for farmers. Fencing lo`i or farm perimeters does not fit the spirit or traditional practice of farming kalo where each lo`i cluster is connected to the next farm by water, berms and pathways. However, if dogs remain an unresolved problem in your area, you may want to implement this practice on your farm, or jointly with your neighbors.
1. Disease. Domestic ducks are susceptible to botulism in the same way that wild waterbird populations are in Hawai`i. Contaminated water sources are a vector for this disease and can cause the loss of an entire flock within a few days. Providing a clean, dry shelter and clean drinking and bathing water sources will reduce the likelihood of a botulism outbreak. Keep your ducks from drinking or playing in stagnant, polluted water sources (ie. effluent ponds or water where any dead animal/fish has been observed). Clean their bowls regularly.
Moldy or old feed, particularly fishmeal or peanut-based feeds, may be the source of toxins that cause high mortality in a flock, especially ducklings.
a. Isolation. Any duck that shows signs of illness should be isolated from the flock; do not transport to or allow to mix with other duck or waterbird populations. Keep a sick duck away from ducklings or juveniles especially.
b. Transport. It is unknown at this time whether domestic ducks in Hawai`i are carriers of avian malaria. Any project that will move ducks from one island to the next should submit a request to be inspected and tested by the DLNR-Division of Forestry and Wildlife for avian malaria.
Every effort should be made by state and federal agencies to support development of a renewable duckling source on each island to eliminate this potential disease transport vector.
2. Crowding. Too many ducks penned up for too long is stressful and the weak ones will suffer.
3. Evening time. Taro farmers from several sites have observed koloa are most active in at dusk and in the evenings. Keep your ducks penned up at night. This will limit potential interactions and equally important protect your ducks from roaming dogs.
III. Working the ducks
A. Duck numbers
1. In an infested lo`i, 12 ducks working daily for 3-4 weeks will bring snails under control. Three to six ducks can maintain a patch once the snail population drops to a lower level. It is important to have some ducklings or juveniles on hand to replace any adults that may be lost to age, dogs, theft or disease.
B. Work patterns
1. The best case scenario is to remain in the area working. Let the ducks out. They will fill up on snails quickly if they are hungry. Then they clean themselves, rest, eat other bugs and grass and will go after the snails again. Train them to go back to their cage at your own signal (ie. whistling, clapping, calling, shaking a grain can).
2. If you can not be at your lo`i for long, let the ducks out for one-half to one hour where there are plenty of snails. Pen them after they have eaten and come back later in the day to let them out again for another cycle.
3. Work from the beginning of your water source towards the most makai portion of your lo`i. Pick large snails and eggs as ducks clean up medium and small snails. For more control over which lo`i the ducks will feed in first, use a 2ft high moveable fence to isolate the patches you want cleaned and contain the ducks.
4. Prior to planting, a series of dry-downs and flooding will effectively bring snails to the surface. Remove the largest ones by hand and let the ducks go after the smaller ones. They will fertilize the patch in the process.
Engilis, A., Jr., and Uyehara. 2005. Identification of Hybrid Hawaiian Duck (Koloa) x Mallards: An Aid to the Recovery of Koloa. Presentation at 2005 Wetland Management in the Hawaiian Islands Workshop: Connecting Research and Management. October 6-7, 2005. Kailua, Hawai`i.
How to Clip a Wing:
1. Best done with 2 people - one to hold the bird and the other to clip.
2. Use sharp scissors.
3. Eliminate some of the stress by covering the fowls head with a towel.
4. Clip about 5 of the primary flights off one wing. Do not clip blood feathers among the wing plumage. (New feathers growing in are called bloodfeathers. Before clipping, look for white- shafted young feathers among the plumage. Never cut bloodfeathers as it is a direct line to blood vessels and the bird can bleed to death. Wait to clip them until they are fully grown out.)
The best time to clip is right after a molt when all feathers are fully grown out. Clipping does not hurt when done properly. Clipping will need to be done after each molt as cut feathers are replaced with full feathers again.
How to remove a wing tip:
A pinioning guide from the Book Wild Waterfowl And Its Captive Management Volume I, published by the Game Bird Gazette magazine provides a diagram for removal of the wing tip. The book recommends pinioning be done by a qualified veterinarian or under the direction of a veterinarian, however, many farmers do the work themselves.
The best time to pinion a bird is the day after a hatch. There will be little blood at this stage and it can be done quickly with sharp scissors.
1. Use a good sharp pair of boning scissors or a pair of my electrical side cutters.
2. Take the bird by left hand and hold them with their heads tucked under, using your arm and hand to keep them still.
3. Pull the wing out and in one quick cut just in front of the small thumb feathers, leaving that batch of feathers to act a protection on the new cut.
4. Cut the wing bone and all primary feathers off.
5. Treat the cut and release the bird to a clean area with clean water to heal. Bleeding should stop within a minute or two.