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Summary
Flesh-footed shearwater population monitoring on Ohinau and Lady Alice Islands
This report covers the population monitoring of flesh-footed shearwaters (Puffinus carneipes) on Ohinau and Lady Alice Islands carried out under Conservation Services Programme project POP2015-02. This is the first year of intensive monitoring for the entirety of the breeding season for both populations.
Some preliminary monitoring and banding of the Ohinau Island population was conducted in April/May 2016. A total of 661 birds were banded on Ohinau Island and 379 on Lady Alice Island during this season. A total of 229 study burrows were monitored on Ohinau Island and 179 on Lady Alice Island.
A further 35 burrows on Ohinau Island and 30 burrows on Lady Alice Island were monitored by burrowscope only to assess if there was any effects of our monitoring. No effect was detected with burrowscope burrows having a lower breeding success than study burrows. At least one partner was identified in 91% and 72% of all study burrows for Ohinau Island and Lady Alice Island respectively.
Three hundred and ninety-nine eggs were laid in all burrows combined and the overall breeding success (chicks that are likely to survive to fledging) for the season was 49.1%. This result is the first measured for a New Zealand population of flesh-footed shearwaters. It is similar to that measured in some Australian populations, but we suspect that due to heavy rain and possible flooding of burrows it is slightly lower than could normally be expected.
The high number of grey-faced petrels (Pterodroma gouldi) present on both islands is possibly also affecting breeding success. Ongoing and repeated monitoring of both islands will continue and more robust conclusions about the population trends of flesh-footed shearwaters in New Zealand can be made.
Population estimate of Flesh-footed shearwaters on Middle Island
During a field trip to Middle Island, from 5-10 January 2017, a total of 25 transects recorded burrow density of Flesh-footed Shearwaters at 0.0745 burrows/m². Burrow density varied for the three vegetation types found on Middle Island, with burrow density in the Karo-Taupata scrub estimated at 0.089 burrows/m²; the Wharangi-Mahoe forest at 0.146 burrows/m²; and in the Milk Tree Forest at 0.025 burrows/m².
Night work also indicated that Flesh-footed Shearwater numbers vary amongst vegetation type, with more birds recorded in Karo-Taupata scrub and Wharangi-Mahoe forest than the Milk Tree forest on the plateaus. From burrows where their contents could be determined using a burrowscope, burrow occupancy was calculated as 71.8%.
Area calculations for the three vegetation types estimate that there is 63,360m²of Karo-Taupata scrub, 13,486m² of Wharangi-Mahoe forest, and 19,954m² of Milk Tree forest on Middle Island. Stratifying for the three vegetation types, and correcting for burrow occupancy the population of Flesh-footed Shearwaters on Middle Island is estimated to be 5,822 breeding pairs (95% confidence interval 2,400-9,244).
This confirms that Middle Island has the largest Flesh-footed Shearwater population in New Zealand.
The only previous population estimate for Middle Island, 3,000 breeding pairs, was based on data collected in 2003; re-analysis of this data, stratifying for vegetation and using 2017 burrow occupancy rates, estimates the 2003 population was 4,441 breeding pairs; within the confidence interval of the 2017 results.
Foraging distribution and behaviour of Flesh-footed shearwaters breeding on Lady Alice Island
The flesh-footed shearwater (Puffinus carneipes) breeds around New Zealand and Australia and is currently at risk from a range of threats, including fisheries by-catch and plastic ingestion. Recent population estimates indicate that this species is declining globally. New Zealand is a key population centre for this species, with many breeding colonies located on off-shore islands, including Lady Alice Island.
The results presented here are initial findings at the start of a longer tracking project aimed at building a comprehensive understanding of flesh-footed shearwaters spatial distribution around New Zealand. This study is being carried out under the Conservation Services Programme project POP2015-02. GPS devices, combined with saltwater immersion loggers, were deployed on over 40 individual birds breeding on Lady Alice Island in February 2017.
Combined tracking allowed identification of key areas used for foraging behaviour during the early chick rearing period. Many individuals travelled to areas within 400km of the breeding colony, along the east coast of North Island, but some flew more than 1000km away from New Zealand in single foraging trips. During these excursions, the majority of time was spent resting on the surface of the water, indicating efficient transit times between foraging areas.
Future combined tracking work at different parts of the breeding season will provide more accurate estimates of key areas utilised by flesh-footed shearwaters, and hopefully help prioritise conservation policies for this species.
Publication information
Crowe, P.; Bell, M.; Kirk, H.; Burgin, D. 2017. Flesh-footed shearwater population monitoring on Ohinau and Lady Alice Islands, 2016/17 report. Report prepared by Wildlife Management International Limited for the New Zealand Department of Conservation, Wellington. 20p.
Bell, M.D.; Boyle, D.P. 2017. Population estimate of Flesh-footed Shearwaters on Middle Island. Report prepared by Wildlife Management International Limited for the New Zealand Department of Conservation, Wellington. 12p.
Kirk, H.; Crowe, P.; Bell, M. 2017. Foraging distribution and behaviour of flesh-footed shearwaters (Puffinus carneipes) breeding on Lady Alice Island – February 2017. Report prepared by Wildlife Management International Limited for the New Zealand Department of Conservation, Wellington. 24p.