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Winter Quarterly Report for Ka’elepulu Wetland, 12-2005 through 2-2006

Introduction

Through December and January rainfall was very light and water levels were stable. However, from mid February through mid March over 17 inches of rain fell. Severe flooding occurred in March on all islands. On 2-19 flood waters completely covered all of the islands. The following weeks saw water levels fluxuate greatly. During the very low water periods, just prior to the March deadline for cessation of work on the islands, opportunities arose for mowing of some normally flooded batis areas makai of the islands. Large areas for stilt feeding and many new sites for potential nesting were cleared.


Vegetation Management

Work continued with the preparation of fringe zones on all islands. Greatest attention was given to islands two and three where much of the waters edge was still occupied by impenetrable growths of batis. The island crowns were sprayed as needed to suppress emergent weeds.

Stilt Nest Site “Foot Print”
A close examination of last year’s known stilt nest sites was made. Instead of nesting in large open areas set back from the water’s edge, stilts chose smaller patches with emergent batis just leeward of open water. This “footprint” was reproduced in twelve new areas next to cleared “fringe” habitats. These potential nest sites were spaced all along the mauka bank of the stream and the mauka edge of the ponds and flats. The mauka edges of these bodies of water lie to the lee of the open water. (It is observed that birds always start flight by jumping into the wind and thought that they may choose nest sites with a consideration of escape from predators.)

Brush removal along the stream bank starting at the floating docks was completed. Paspalum planted at the water’s edge along the moat and stream bank became well established and provided feeding habitat The Bulboshonus sp. that has been planted with the grass grows well. Mowing of the moat bank covered with Widelia and other invasive plants is done principally by Ron Walker who volunteers his Friday mornings and his weed whacker. Freshly mowed areas are frequented by stilts and other residents of the wetland.

Mangrove seedlings continued to be removed. These were most accessable by canoe during high water periods near the end of the quarter.
The native plantings near the dock continue to grow. New growth has appeared in the Bulboshonus patches. Cyperus sp. sedges, previously found along the makai bank of the stream channel, near Al’s dock, have been cultivated from seed collected prior to the die off there. These plants in dibble tubes should be ready for outplanting next quarter.

Island Crown Weed Recruitment and native plants

The flood that covered all islands in February deposited large numbers of weed seeds on the island crowns just a few days before the USACE guidelines forbade management work on the islands. Unfortunately these invasive plants now have six months to grow before control work can resume.
Two species of native plants surviving on the crowns have been tentatively identified. These are drought tolerant indigenous species, Portulaca lutea and Heliotropium curassavicum. When work on the islands resumes in the Fall propagation efforts using seeds may be undertaken with the goal of conserving a native plant community.

Other likely candidate species for the community include Sesuvium portulocastrum, and the grass Sporobolus virginicus. Interestingly, a unique subspecies of S. virginicus inhabits the windward Oahu coast. The Manual of Flowering Plants, Wagner, Herbst, Sohmer, pg 1597, says “Sporobolus virginicus var. phleoides was described for plants on windward beaches of Oahu, and was distinguished by having shorter and thicker inflorescences.” Kailua beach may be an appropriate source of seeds for this unique grass. In partnership with other wetland managers in the watershed, species may be transplanted from nearby wetlands.

Bacopa Growth
The Bacopa. monnieri., named ai’ai in Hawaiian, has begun a period of re-growth as the rainfall increased at the end of the quarter. Growing patches of it are found along the moat and stream banks. If these become large enough to provide bridges to the islands for predators the patches may be controlled. No apparent die-off events have been observed this quarter.

Predator Control and Predation

Frog Control
Bullfrogs continued to be caught occasionally on the stream bank throughout the quarter. After Februarys heavy rains the catch rate increased significantly. Mature males and females are caught, never smaller juvenile frogs. Calling frogs are currently heard on both sides of island two and island one. This represents an expansion of their range from the stream. Plans are being made for the construction of another trap.

Rat Control
Rat bait stations were maintained weekly. Because they are accessed by canoe during breeding season some have been relocated to be more accessable. During the several floods all of the stations were covered in water and the baits were ruined. Traps were then placed in higher locations, occasionally on top of batis clumps. Several stations were lost in the March flood and were replaced.

Opala Patrol

Trash and spray paint cans were collected during the period quarter. Cans were especially abundant after the February flood. As usual few of the cans had spray caps on them. We have learned that graffiti is usually done with specialized spray tops, explaining the absence of the tops and confirming that these cans are probably from people doing graffiti.

Bird Observations

Species of Note

Kolea, wandering tattlers and Ruddy Turnstones continue to use the habitat. Black bellied plovers, which are very similar to golden plover but frequent mud flats and coastal habitats, have been identified. Stilts have been abundant this quarter with over 30 individuals counted in February. There seems to be a transient and a resident group within the large population. The resident group is thought to be the breeding population. Included in the resident group is the female with three bands which nested successfully on island one last year. She has again been frequenting island one.
One stilt with a broken hip or leg was observed over a period of weeks. This individual had a band on its good leg. Bill Carlisle has been keeping track of the stilts and has compiled a table of his observations. Stilt courtship behaviour has been infrequent this quarter but has become common in May.

Water Level and Rainfall Observations

The data from the water level gauge and rainfall gauge are reported separately in an Excel file with a graph. For most of the quarter rainfall was relatively low and the sand berm at Kailua beach was not significantly breached to lower the water level. The City and County opens the berm monthly at mid month but, unless this coincides with a heavy rainfall, the level is not greatly reduced. This is thought to be because the flow rate through the C&C gap is not sufficient to cause a drop in the lake level nor to prevent the resealing of the gap by natural beach migration of sand.
When heavy rains fall, the lake level appears to rise quickly in proportion to rainfall. Flood peak follows the rainfall event within a few hours due to the small size of the watershed and the channelization of the urban areas. When some critical point is reached the stream at Kailua Beach breaches the sand berm and a large volume of flood water drains from the lake. The lake level then drops to a point where equilibrium with the ocean tides through the mouth of the stream is established. Then a period of days or weeks is required for the sand berm to naturally rebuild and the lake level to become relatively stable once again. After the berm is rebuilt, water levels may rise with rainfall if the input is not enough to overtop the berm at the mouth of the stream and initiate another cycle of rise-drop-equilibration-stabelization.
During the post-flood period when the lake levels may mirror oceans levels. The water can be low enough so that the dike bottom is exposed and land bridges across to bird habitats are exposed. This is a concern for predator control.

Breeding Activity

Feral Birds
A pair of white geese from the resident flock began nesting in January. Eggs are laid every other day and have been collected through February and March. One or two eggs are kept in the nest so as to promote laying and avoid abandonment of the nest. In
Last year eggs were simply oiled after the female began incubation and after several weeks the nest was abandoned and the pair nested in an inaccessible site. Those eggs hatched and produced a flock of goslings. To avoid nest abandonment the egg laying period is being prolonged for 8 weeks by the collection of eggs described above. At the end of March eggs will be left in the nest and will be oiled two weeks after incubation begins. Hatching is assumed to occur at three weeks. It is hoped that when the eggs and nest are eventually abandoned that the birds will not re-nest this season.
Mallards have successfully hatched several broods this quarter. Mortality rates continue to be 100% in most cases. Night heron predation is most likely the principal cause of mortality. Some clutches of eggs have been discovered and oiled. The flood in February inundated two known mallard nest sites.

Native Birds
In January, most likely, a brood of gallinules hatched in an Island Two territory. At the end of February three chicks that appeared almost fledged were reported by Bill Carlisle. These birds were from a second brood. There has been a lot of territorial and courtship behaviour among the gallinules this quarter.
Coots have been nesting but no chicks have been seen as of March. All of the known nests were flooded in February.

Locations of Nest Sites

Nest sites were not mapped this quarter but were typically found in the same areas as previously reported. Study of stilt nesting in the newly prepared sites will be undertaken when feasible next quarter.

Summary

Habitat management during the Winter Quarter was conducted with the objective of providing better feeding and nesting for stilts during variable water levels. Rainfall and resulting water levels in the wetland were quantified. No disease outbreaks or new predator problems were observed. Heavy rainfall caused temporary flooding of habitat and nests at the end of the quarter and caused an expansion of the bull frog range.

Previous Reports

Winter 2004

Spring 2005

Summer 2005

Fall 2005

 
 
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