The conservation status of Hutton's shearwater (Puffinus huttoni) at Shearwater Stream, Kaikoura, New Zealand: a small population at risk?

Hutton's shearwater (Puffinus huttoni) is a burrowing petrel endemic to the alpine zone of the Seaward Kaikoura Ranges, New Zealand. In November 2019, we accessed an understudied breeding colony at Shearwater Stream in the Puhi Peaks Nature Reserve for the first time since a Mw 7.8 earthquake struck the region in 2016. We measured population parameters and carried out a geomorphological assessment. We estimate that the Shearwater Stream colony supports approximately 3,000 breeding pairs. Ground deformation attributed to the 2016 earthquake did not explain the discrepancy between this estimate and the commonly cited (pre-quake) population estimate of similar to 8,000 pairs. We highlight the limitations of extrapolated population parameters and of using vegetation cover as a coarse proxy for colony area. We discuss how low burrow occupancy and long-term reductions in the availability of suitable habitat indicate a population at risk of decline. We highlight how stable long-term data for burrow density and breeding success may not be reliable indicators of population health at Shearwater Stream.