Aerial survey for Gibson's albatross on Adams Island 2016

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POP2015-03: Objective 1a: Aerial Survey for Gibson's albatross on Adams Island 2016 (PDF, 1,333K)

Summary

This study sought to build on earlier exploratory aerial census work and refine recommendations for robustly estimating the total population size of Gibson's albatross at Adams Island, where 95% of the global population breed.

In January, 2016, we undertook a partial survey of Adams Island using aerial photography. We trialled the use of a vertically-oriented camera that was GPS linked to take a series of photographs to estimate the number of Gibson's albatross breeding in defined areas.

These areas overlapped an area that was ground-counted at the time of the photography, which allowed ground truthing and comparison with ground survey methods.

Using a Squirrel AS350B3 helicopter, we flew a series of transects spaced at 70 m centres that ran across the terrain from east to west, and used the aerial guidance system TracMap Flight Pro to define and accurately fly the transects.The transects were flown over the terrain under specific flight and photographic specifications: 

Between 80 and 100 photos covering each of three areas were selected for analysis. These were uploaded to an Internet-based online geo-referencing interface Maps Made Easy for stitching and geo-referencing. The high-resolution maps produced by this process were then analysed using the image editing software Adobe Photoshop and the GIS program QGIS for counting as well as spatially locating birds and or nests.

Aerial assessment identified a total of 129 birds ashore on the three maps. Ground-truthing showed that only 95 (74%) of these birds at the time of the aerial count, or subsequently, were nesting. The other 34 birds (26%) were therefore loafing at the time of the aerial count.

The resolution of the images was substantially improved over that obtained in aerial photography in 2015, leading to very little uncertainty separating nesting albatrosses from the large number of white rocks that are present at this site.

The camera/lens/flight height combinations used in this study provide a suitable methodology to undertake a count of Gibson's albatross on Adams Island using aerial photography. However, substantial helicopter flying time and data analysis would be required to do this for the entire island, and the ever-changing nature of the weather on Adams Island means it may not be possible to fly all breeding areas in one breeding season.

Development of a survey schedule that plans to survey the island over three or four years would be appropriate, with flexibility provided so that advantage can be taken of good weather conditions when they arise.

Publication information

Baker, G.B., Jensz, K., Elliot, G. & Walker, K. 2017. Aerial survey for Gibson's albatross on Adams Island, 2016. Report prepared for the New Zealand Department of Conservation, Wellington. 12p.