Keālia Pond Habitat Restoration
The refuge’s goal to protect endangered Hawaiian waterbirds includes enhancing and restoring the habitat they depend upon. A majority of the preferred habitat has been encroached upon by nonnative, invasive plant species that form thick stands which cannot be accessed by birds. Refuge staff and volunteers devote resources to opening up more wetland habitat to increase foraging and nesting areas for birds.
Wetland restoration involves invasive plant control that must be maintained on a frequent basis due to the year-round growing season. Although a majority of these projects are for the benefit of waterbirds, the Kanuimanu Pond restoration project also benefits visitor access.
Kanuimanu Ponds restoration
By 2004, the Kanuimanu Ponds were showing their age. After 34 years, the levees were extensively eroded and covered with invasive pickleweed, Batis maritima. The thick growth prevented young birds from moving between the ponds in attempts to gain access to foraging areas. During winter months when water level was high, the individual ponds would become connected as water flooded over the levees. Not only was this detrimental to the infrastructure, it limited visitors’ access.
In partnership with Ducks Unlimited, Inc., reconstruction of the ponds was initiated in 2004. The levees were built up in elevation and widened to prevent flooding. Slopes were formed to provide shallow water when ponds were full with water. The most benefit to waterbirds was the installation of a water distribution line to pump water into separate ponds, particularly during the dry season. Prior to the work, all invasive plants were removed. Refuge volunteers have out-planted native vegetation on the slopes that provides foraging area for Hawaiian coots and young stilts can walk through to move between ponds.
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| Before reconstruction of Kanuimanu ponds - Photo credit USFWS |
After reconstruction of Kanuimanu ponds - Photo credit USFWS |
Mangrove removal
Red mangrove along the northeast shore of the main pond have posed a problem since the refuge was established. The old stand of trees were so dense that nothing grew under its canopy and it served as a rookery for nonnative cattle egrets that pose a threat to nesting waterbirds. When the mangrove was removed, the native sedge kaluhā spread and established in its place. Water coverage in this area during winter has opened the area for use by Hawaiian coots and migratory waterfowl.
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| Main pond before mangrove stand removal - Photo credit USFWS |
Main pond after mangrove removal - Photo credit USFWS |
Old Baitfish ponds
The baitfish ponds were constructed in the early 1970’s for aquaculture of baitfish species; however, the use of these ponds for waterbirds was minimal because of the thick coverage of nonnative, invasive plants on the levees and within the ponds. It was difficult to manage the vegetation and water in the six small, individual ponds so during restoration in 2007, all vegetation was removed (excluding small areas of native sedge) and the cross levees were partially removed to form islands. The result was an open pond with islands for nesting and restored water delivery. In 2008, a minimum of seven stilt pairs nested successfully.
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| Before restoration of Baitfish ponds - Photo credit USFWS |
After restoration of Baitfish ponds - Photo credit USFWS |
Restoration efforts are continuous and pose challenges to maintain in these lowlands where the infusion of invasive plants is continuous. Other problem plants on the refuge include California bulrush (Scirpus), California grass, Indian marsh fleabane, Washingtonia palms, and large acreage of pickleweed (Batis maritima) covering the mudflats.
