Early Summer Quarterly Report for Ka’elepulu Wetland, 3-27-05 to 6-25-05

Introduction

During April, May, and June breeding activity for all birds continued. A pair of stilts successfully reared three or four young to 35 days old. The chicks are well camouflaged and dispersed over island one making counting difficult.
Heavy rainfalls became less frequent and the day length and temperatures increased. Water levels were typically low or moderate. Vegetation management ceased on the islands and continued on the edge of the moat.
An effective rat control program was implemented and some bullfrog control efforts were initiated.

Vegetation Management

Removal of the Pluchia indica and other non-native flora on the bank of the moat was the focus of vegetation control this quarter. Work on the islands was suspended on March 1st. The very thick Wiedelia sp. mat was cut back with the invaluable help of Ron Walker. Ron also assisted in the removal of the tall pluchia at the edge of the water near the street side of the moat and all other aspects of management. Hugo DeVries in many trips hauled more than a half ton of vegetation from these areas to Kailua’s green waste facility. Other neighbors assisted with the effort as well.
Pluchia and california grass overhanging open water provides cover for predatory bullfrogs and the removal of this habitat contributes to predator control efforts.
An estimated 400 mangrove seedlings were removed this quarter when water levels were high enough to make sweeps around the islands. Most of these were small and recently rooted in the mud.
The native plantings near the dock continue to grow and the Bulboshonus sp. being grown in the nursery were planted along the moat near the mauka road. The sprouted sedge seedlings have spread readily by rhizomes in their pots. Their seeds seem to require an extended dry period followed by wet to initiate germination.

Predator Control and Predation

Live trapping for rats, cats, and mongoose was conducted biweekly along the moat and in adjacent dry land areas. By the moat three rats and no mongoose were captured in 70 trap days during the quarter. In the brushy area near the house site 7 rats and no mongoose were caught in 80 trap days. Cats have not been caught in any quarter thus far. In mid-June the live trapping program was suspended because the upland rat control program seemed to be successful and the catch rate fell to zero when the baiting program became established.

Bullfrogs continue to be heard near the banks of island one. During wet periods they were also heard along the makai edge of island two. A fishing attempt along the perimeter of the islands was attempted without catching anything. Netting them with the aid of refugia traps, made of floating cups, was tried without success. No frogs occupied the cups set among the fringe vegetation. Cane toads occasionally tripped the live traps and a bullfrog was also captured in a live trap. Another bullfrog was caught by hand this quarter.
In mid-June a report of successful bullfrog control at Campbell Wildlife Refuge was heard. There they were using 20-inch diameter funnel traps and had captured hundreds of frogs. Survival of chicks was reported to have improved greatly as a result of their bullfrog control. A trap was built on 6/17 and caught a frog in the first 2 days of deployment. None were caught over the ensuing week however and the trap will be deployed elsewhere. More traps will be built and deployed in July.

The Black Crowned Night Heron, Aku, is a native bird that has been seen preying upon ducklings and coot chicks this quarter. They are suspected to be the principal cause of the complete mortality of ducklings to date. Counts of eleven broods of ducklings over the last 6-month period indicate that no ducklings have survived for longer than four weeks and few if any survive for three weeks. We estimate that the aku may be eating one duckling a day from each brood of ducklings. There may be other sources of predation, like bullfrogs. A detailed account of mortality rates was made last quarter.

Rat Control

In April a rat baiting protocol was initiated. All stations were monitored biweekly from
4/11 to 5/17 to determine the effectiveness of the program. After one or two spikes in bait consumption rates, the amount of diphacinone based bait being consumed dropped to very low levels. This indicated that the population was controlled on the islands using this rodenticide and protocol. Four more bait stations were added to the set to ensure good coverage around prime nesting areas. A graph of the first month’s consumption rate follows. After the start-up phase stations were checked and serviced weekly.

Rat bait consumption rates at six stations

Dipacinone based rodenticide was stocked in six stations ringing the perimeter of the islands. To determine the effectiveness of the program the consumption of bait was closely monitored for the first month. One or two spikes occurred at each station during the first three weeks. A dash data point indicates that all bait was eaten, diamond that some was left in the station.

Opala Patrol

Trash and spray paint cans were collected semi-weekly during the quarter. The edges of the habitat were surveyed for trash and mangrove seedlings by canoe, usually on Fridays during bait station monitoring. Approximately one hundred spray paint cans were washed down the stream into the wetland during this quarter, half the number from last quarter.

Bird Observations

Species of Note

Few migratory birds were seen this quarter.

A strange phenomenon was observed this quarter. Two stilts were found with oysters clamped onto their toes on 4/28 and 5/2 respectively. This happened during a period of very low water level when the beds of oysters on the lake’s mud flats were exposed. In both cases the birds had flown with the attached oyster to resting-places along the edge of the stream. Both birds were captured and the oysters manually removed. The first was treated by a vet for a mutilated tarsal and the second was released immediately without treatment. Both were unbanded females and were possibly two of the three females in the resident colony at Ka’elepulu Wetland. They seemed to recover normally. On 6/24 an unbanded female stilt was seen limping a bit after a period of low water but no oyster was attached to an apparently injured left foot.
It is recommended that stilts with oysters clamped on their toes be captured as soon as possible before the toes experience compound fractures and severe tissue damage as was observed in the first instance. The bird was first seen in the morning and captured in the evening.
The end of the toe of the first bird was amputated by a veterinarian. The bird was released that same evening so it could feed and drink. Return to the wetland was judged to be important to facilitate recovery of the severely exhausted bird.

During the first period of very low water at the end of April a flock of 14 night herons was observed feeding in the shallow waters of the lake. Stranded dead fish may have attracted them. A fish kill in the lake was reported during this period.

Breeding activity

After 3/1, regular inspection of nests on the islands was suspended per the USACE instructions to stay off of the islands where stilts may be nesting. Nest observations are more sporadic as a result. The number of nest sites found since April is an undercount.

Feral Birds

The feral geese continue to be fed by a marsh neighbor at the northern end of the wetland. The white geese there nested successfully in the mangroves. Three goslings survived the first week and one was observed the following week because the birds are difficult to view from the wetland. The fate of the remaining gosling is not currently known. The initial number of hatchlings is not known.

Mallards have successfully hatched approximately a half dozen broods. This nesting rate is comparable with the October to December and the January to March rates. However, during the previous two quarters nests were actively searched for and eggs were oiled. Several of the broods that frequented the mauka waterways had one yellow duckling showing the genetic influence of a white commercial duck variety in that area. Nest locations on the islands this quarter are not known because, as of the beginning of March, we stayed off of the islands. One exception is that of a nest discovered near the bait station by Bill’s canoe on the makai edge of the stream by island two.

Native Birds

Stilts nested successfully in May. Four newly hatched chicks were seen on island one by Bill Carlile 22 days after the beginning of nesting behaviour. The stilts hatched on 5/20 judging by the initiation of aggressive parental defensive behaviour. The female is a banded bird. Photos of the chicks and parents are posted on the web at http://www.kaelepuluwetland.com/stilts/

All chicks survived for a month and two survive at the time of this writing two months after hatching.

Coot nests were observed along the fringe of the islands during bait station servicing. Their locations, egg numbers, and dates are amended to the map of the Wetland Schematic attached as a jpg file to this report. Coots continue to nest at a rate higher or a comparable to last quarter. More chicks seem to be surviving to an older age but this has not been quantified.

On 3/21 four gallinule chicks were first observed in the california grass fringe by the mouth of the stream. Two of these chicks were seen again on 4/15. These two chicks have been watched over the quarter developing flight feathers and growing well. They have survived for three months.
Three other gallinule broods have been observed. Two families with chicks of a comparable age to the first were seen in May. The families seemed to occupy discrete territories. One pair with a single chick was seen up the stream by the canoe storage area. Another with two chicks was on island two. These two chicks may be from one of the two nests with eggs observed on 2/28. (See last quarter’s report.) The third and youngest family was seen feeding on the mauka edge of island one on 5/16 and 5/20. A very young dead gallinule chick, probably from this brood, was found floating by the dock area earlier. The cause of death was not apparent but a great deal of fighting among the adults in the vicinity was observed earlier.

Locations of Nest Sites

A map of nest sites has been amended when new nests are located. No observations from the island’s interior are available since March 1st so the map should be used only qualitatively. It is transmitted as a separate jpg attachment to accompany the following text.
Notably, there was no nesting by any species on the main part of Island One. This is an area favored by the flock of feral geese. These large birds may inhibit nesting in areas they frequent by invading nest sites and driving off females engaged in nesting behavior.

Submitted, 6/25/05
Larry Abbott

Figure 3, Known Nest Sites for 04-05 Season

Coots:
C1- Rebuilt nest by pair flooded earlier on island one. Five eggs observed on 2/12.
C2- Rebuilt nest by pair flooded earlier on island three. This earlier nest had one dead chick. On 2/7 two chicks had hatched and three eggs were not yet hatched. No eggs were in nest on Friday so all probably hatched. Parent on nest has a red spot on face shield.
C3- Rebuilt nest by pair flooded earlier. All four eggs hatched and chicks were seen at the nest and elsewhere by Bill.
C4-New nest discovered two weeks ago, may not be active.
C5-New nest. Five eggs were observed on 2/12
C6-New nest site. No eggs observed.
C7- Nest site where two drowned eggs were found 3/21.
Gallinules:
G1- Gallinule nest with 6 eggs found 2/28
G2- Gallinule nest with 2 eggs found 2/28
Goose- 16 eggs oiled on 2/21 and again 3/21, a nest with an unknown number of eggs produced at least three white goslings early in June. Survival was down to one within a month.
M- mallard nests since September