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Endangered waterbird and wetland status, Kaloko-Honokohau National Historical Park, Hawai'i Island
|Title:||Endangered waterbird and wetland status, Kaloko-Honokohau National Historical Park, Hawai'i Island|
|Authors:||Morin, Marie P.|
|LC Subject Headings:||Endangered species -- Hawaii -- Hawaii Island.|
Kaloko-Honokohau National Historical Park (Hawaii)
Rare birds -- Hawaii -- Hawaii Island.
Water birds -- Hawaii -- Hawaii Island.
Wetland management -- Hawaii -- Hawaii Island.
|Date Issued:||Jun 1998|
|Publisher:||Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa, Department of Botany|
|Citation:||Morin MP. 1998. Endangered waterbird and wetland status, Kaloko-Honokohau National Historical Park, Hawai'i Island. Honolulu (HI): Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa, Department of Botany. PCSU Technical Report, 119.|
|Abstract:||The endangered waterbirds of Kaloko-Honokohau National Historical Park (KAHO) were studied from February 1992 through 1995, a study begun in conjunction with other avian surveys done during 1992-93 at the three National Park units in west Hawai'i Island (Morin 1996a, 1996b, 1996c). Other simultaneous surveys studied invertebrates, mammals, and vegetation (David Foote pers. comm.; Charles Stone pers. comm.; Pratt and Abbott 1996a, 1996b, 1996c) at those same sites. Endangered Hawaiian Coots or 'Alae ke'oke'o (Fulica alai) and endangered Hawaiian Stilts or Ae'o (Himantopus mexicanus knudseni) are resident, endemic species and breed at KAHO. Two other resident waterbirds also regularly breed there: the indigenous Black-crowned Night-Heron or 'Auku'u (Nycticorax nycticorax hoactli) and the|
Pied-billed Grebe (Podilymbus podiceps). The endangered Hawaiian Moorhen or 'Alae'ula (Gallinula chloropus sandvicensis) is believed to have been extirpated on Hawai'i Island in the early 1900s (Banko 1987a). The fourth endangered Hawaiian waterbird species, the Hawaiian Duck or Koloa (Anas wyvilliana) has never been confirmed from KAHO's wetlands. Two nonnative waterbirds established on Hawai'i Island sometimes visit KAHO, but there are no records they have ever bred there: the Mallard, Anas platyrhynchos, and Cattle Egret, Bubulcus ibis. In addition to the previously mentioned species, long-term bird sighting records indicate that at least 2 species of migratory geese, 15 species of migratory ducks, 23 species of migratory shorebirds, 11 species of gulls and terns, and 3 other migrant or vagrant species have visited KAHO's wetlands (Morin 1996b). Northern Shovelers (Anas clypeata) were the most abundant migrant duck. Waterbird censuses were made at least weekly in the two KAHO fishponds, 'Aimakapa and Kaloko, for most of the period 1992 through July 1994, and at least twice a month from August 1994 through February 1995. Hawaiian Stilts used both KAHO fishponds, but Hawaiian Coots and migratory ducks did not utilize Kaloko Fishpond, probably due to its deeper water, higher salinity, and inappropriate vegetation. From 1992 through 1994, surveys for waterbird nests were made at both fishponds approximately weekly during the peak breeding season of February through July, and less often otherwise. Endangered Stilt and Coot nests were found only at 'Aimakapa Fishpond, and were concentrated on the northern, southern, and eastern shorelines, coincidentally in the areas most isolated from visitor use. In 1992 no Hawaiian Stilt chicks were found, but after predator control was begun in 1993, Hawaiian Stilts successfully fledged chicks. Hawaiian Coots had poorer recruitment success even with terrestrial predator control, and possible causes include predation on new chicks by large fish in 'Aimakapa Fishpond. An outbreak of avian botulism caused a large die-off of endangered waterbirds during 1994. Hawaiian Coot mortality at 'Aimakapa Fishpond appeared to be almost 100%, but Hawaiian Stilts sustained lower mortality (Morin 1996d). By December 1995, Hawaiian Coot and Stilt counts were returning to normal at 'Aimakapa Fishpond, but migratory waterfowl counts remained low. From February 1992 through February 1995 counts of human visitors were made at each fishpond during the bird censuses, and visitor use categorized. Highest visitor counts were on
the beach just west of 'Aimakapa Fishpond, and beach-related activities such as sunbathing appeared to be the most frequent visitor use there. The presence of dogs (usually pets) next to or in the fishponds decreased from 1993 to 1995, probably due to a posted leash law enforced by the Park since approximately 1994. Predator control at 'Aimakapa Fishpond from February 1993 through December 1994 removed 290 mongooses (Herpestes auropunctatus), but also a few cats (Felis catus) and a few black rats (Rattus rattus). Hawaiian Stilt chick survival appeared to benefit from predator
removal. Experimental wetland weed removal test plots were made and artificial nesting platforms (designed to reduce waterbird nest loss due to frequent flooding and predation) were installed during late 1992 through 1994. Artificial floating nest platforms were readily accepted by both endangered waterbird species, but an adequate anchoring system has yet to be devised. Primarily in Kaloko Fishpond, non-native red mangrove (Rhizophora mangle) removal was ongoing during 1992 and 1993. After mudflats became exposed again, Hawaiian Stilts began to reuse those parts of Kaloko Fishpond until the mudflats were reinvaded by the non-native pickleweed, Batis maritima. The removal of smaller mangrove infestations also occurred at 'Aimakapa Fishpond and elsewhere in other KAHO wetland and shoreline areas. KAHO's fishponds and associated wetlands are an important breeding, resting, and feeding site for native endangered waterbirds and are also very important as an overwintering and stopover area for migratory and vagrant waterbirds (Medeiros 1958) and shorebirds. 'Aimakapa and 'Opae'ula (Makalawena) Fishponds taken together have been reported to maintain over 95% of the Stilts and 90% of the Coots for Hawai'i lsland (Paton et al. 1985). The author has estimated that during 1992-1994 approximately 70-80% of the Hawaiian Coots and 50% of the Hawaiian Stilts for Hawai'i lsland were maintained at KAHO's wetlands (Morin 1996d). Ecosystem-wide hydrology is poorly understood for west Hawai'i Island. Ongoing waterrelated issues, such as upslope deforestation and non-point source pollution, are impacting brackish water fishponds and other wetlands such as anchialine pools along the Kona coast. In addition, most current and potential waterbird habitat in west Hawai'i lsland is not being managed for waterbirds. Frequent, widespread, and close disturbance by humans, vehicles, or pets and feral animals (e.g., dogs, cats) in or next to these wetlands will probably cause the reduction or elimination of endangered waterbird reproduction, and a reduction in numbers and/or types of other waterbirds and shorebirds known to frequent the wetlands, due to increased mortality and the disruption of feeding. Wetland pestiferous alien plant control, and vigorous predator control (e.g., mongooses and cats) will help to stabilize and reverse the wetland ecosystems' ongoing degradation. The future of waterbirds in west Hawai'i lsland depends upon proactive wetland management at KAHO and nearby sites regularly visited by these same birds.
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|Appears in Collections:||
The PCSU and HPI-CESU Technical Reports 1974 - current|
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