A record breeding season for black stilts in the wild

Forest and Bird, Volume 14, Issue 6, 1 May 1983, Page 30

A record breeding season for black stilts in the wild

By

Ray Pierce

THOUGH the 1982-83 breeding season was generally disappointing for endangered birds in New Zealand, black stilts were reasonably successful. At least 18 chicks were reared in the wild-a record season. Seven were reared at Mailbox Exclosure, six on the Ahuriri River, four at Mick’s Lagoon, and one on the Cass River delta. In addition, two clutches were laid by Captive birds at Mount Bruce Reserve.

THE HIGH PRODUCTIVITY of the wild population resulted primarily from Wildlife Service cross-fostering of early clutches to nests of pied or hybrid stilts mainly in the exclosures and trapping for predators around the renesting pairs of black stilt. This high success was achieved in spite of persistent, cold westerly winds, rain, andsnow throughout the season. Four clutches were lost during a heavy snowfall at Labour Day weekend, and at least four clutches were preyed on at -otner times: "On three separate occasions clutches were successfully rescued as rising flood waters threatened nests, and these eggs were given to foster parents. SELICKY = During the Labour Day weekend whiteout a 3-week-old chick was rescued from Mailbox Exclosure. Up until the Sunday night two chicks had been present with their foster parents-a female hybrid and a male black. On Sunday night the hybrid disappeared (later found dead) and one of the chicks was dead by first light on Monday morning. The surviving chick was being brooded by the black stilt during blizzards and emerged to forage in shallow water during calms, but it was plainly very weak. During one of its foraging bouts a particularly

severe blizzard struck, and the chick was marooned on the down-wind side of the stream. It tried to swim across the stream to its parent, but was forced back to the bank, where it stumbled about at the water’s edge. It was time to act. The chick was collected and transferred to the comparative warmth of the belly skin of its rescuer, then a brooding box, and finally a box beside a fire. There the. chick (‘"Lucky’’) stayed for 3 days, eating up to 2000 insects each day, including about 1500 mayfly larvae brought from the nearby Cass River. Lucky’s destiny was problematical. Ideally the chick

should be returned to its foster parent, but that seemed unlikely to succeed, as the parent’s chicks and mate had been gone for 3 days. But, perhaps... On a warm afternoon, 78 hours after the rescue, Lucky was released into the breeding territory, which the parent was still defending against other stilts. For over 2 hours it was not clear whether there had been acceptance or whether it was going to occur at all. The high frequency of displacement activities performed by the parent suggested that he was confused and, at first, he avoided approaching the chick too closely. Suddenly heavy clouds rolled overhead and the air temperature dropped. Lucky needed warmth. Adult and chick converged on a dry bank and Lucky was brooded.

Acceptance had conclusively occurred. Three weeks later Lucky was recaptured and banded, and shortly after that he took to the air. Exclosure extended Mailbox and Mick’s Lagoon Exclosures were each extended by one-third in area before and after the 1982-83 breeding season, respectively. The Society again funded these fencing projects, and labour was provided by the Wildlife Service. New wetland habitat has been formed in both the extended areas, and this will result in an increase in the numbers of stilts and other water birds using these relatively safe areas for nesting. Both exclosures will continue to be used mainly for cross-fostering of stilt eggs. Attempts are made to ensure that cross-fostered chicks are colour-banded to enable their progress to be followed. This autumn both areas are being grazed by sheep; this will help stem the undesirable proliferation of introduced grasses which has followed the the fencing off of these breeding grounds. a