Population genomics of the ‘rediscovered’ threatened New Zealand storm petrel (Fregetta maoriana) support a single breeding colony

The New Zealand storm petrel (NZSP; Fregetta maoriana), thought to be extinct for over 150 years, was rediscovered in 2003. In 2013, a single NZSP breeding population was identified on Te Hauturu-o-Toi (Little Barrier Island) in the Hauraki Gulf off the east coast of Aotearoa New Zealand's North Island. Expeditions in 2021 to the Far North of New Zealand identified numerous NZSP at-sea over 300 km from Te Hauturu-o-Toi, suggesting that another breeding colony may exist. Blood samples collected from NZSP in the Hauraki Gulf and the Far North were used to generate genomic data. These data were analysed to investigate if individuals from the Far North are genetically differentiated from NZSP from the Hauraki Gulf, and if any individuals from the two locations are close relatives. Analyses revealed that NZSP from the Far North and Hauraki Gulf are not genetically distinct, and possible second-degree relatives were identified between the locations. Genetic diversity estimates indicated low population diversity levels and low effective population size estimates. These results suggest that Te Hauturu-o-Toi may be the only NZSP breeding colony, and the Far North represents a foraging location for NZSP. Sex bias fluctuates through the year but is similar in the two locations, also supporting a lack of population structure and indicating little foraging location bias between the sexes. Further research is needed to confirm whether highly connected or recently established colonies exist. These results highlight the extinction risk for NZSP and the importance of conservation efforts on Te Hauturu-o-Toi.