No evidence that stoats have impacted on Kapiti Island’s birds
Kapiti Island is one of New Zealand’s premier bird sanctuaries. It is home to nationally important populations of little
spotted kiwi, kaka, North Island saddleback, stitchbird and North Island robin, as well as other threatened bird
species. The island was considered to be free of all introduced mammal pests after rats were eradicated in 1996.
However, a stoat was seen there in late 2010, and intensive trapping effort by the Department of Conservation (DOC)
resulted in three stoats being killed during 2011. Inspection and analysis of these animals indicate that a pregnant
female stoat probably reached the island during 2009, and gave birth towards the end of that year. Trapping and survey
efforts continue, and it is unknown whether any stoats are still present.
Saddlebacks are extremely vulnerable to stoat predation as the birds not only nest in tree holes, but roost in holes
every night. Birds that roost, or nest, in holes have little hope of escape when a predator comes in through the only
exit. Saddlebacks are also noisy and conspicuous, and so were expected to be the first bird species to noticeably
decline if stoats started to have an impact on bird populations on Kapiti Island.
Members of the Ornithological Society of New Zealand (OSNZ) completed 3050 ‘five-minute bird counts’ on Kapiti Island
between April 2009 and January 2012. Counts were completed every 3 months during a period completely overlapping with
when stoats were believed to be present. Analyses of these counts revealed no reduction in saddleback range or numbers
on the island over these 3 years, supporting DOC’s survey results indicating that very few if any stoats remain on the
island. “It is great news that saddlebacks continue to thrive on Kapiti Island. This can be attributed to the huge
effort that DOC staff have made to eradicate the invading stoats” said Dr Colin Miskelly of Te Papa, who organised the
counts.
OSNZ established 61 permanent count stations on Kapiti Island in the 1970s, and has undertaken 3-year blocks of counts
approximately once a decade ever since. The OSNZ count team’s transport and food costs were met by DOC as part of
ongoing monitoring of the ecological health of Kapiti Island.
For more information read the blog here.
ENDS