Observations of avifauna on Rēkohu / Wharekauri / Chatham Island, Chatham Islands group, in February 2024

This study examines the avifauna of Rēkohu / Wharekauri / Chatham Island, a remote island group harbouring a diverse range of endemic, indigenous and introduced bird species. Here we report the avifauna observations from a Unitec visit to Rēkohu (8−17 February, 2024). During the ten-day trip, avifauna were recorded from 33 locations. Species diversity was compared between species using the Shannon Diversity Index and Species Evenness. Forty avian species were encountered, most commonly in open farmland and coastal environments. The common starling (Sturnus vulgaris vulgaris) and black swan (Cygnus atratus) were the most frequently observed. Species diversity in 2024 was lower than the avian survey conducted by Unitec in 2023 (H=2.35 vs. H=2.67), likely due to a few species dominating overall counts (E=0.64 vs E=0.73). There were 6x more black swans (n=871) and 3x starlings (n=971) than in the 2023 survey, likely due to favourable weather conditions and increased observer effort in 2024. In contrast, we noted a significant decrease (70.4%, n=50) in white-fronted terns (Sterna striata) in 2024 compared to 2023. Motuhinahina Island had lower species diversity in 2024 than in 2023 (H=1.07 vs. H=1.73), although we had new recordings of white-faced herons (Egretta novaehollandiae) and potentially silvereye (Zosterops lateralis). Counts of Pitt Island Shag (Phalacrocorax featherstonii) and Chatham Island Shag (Leucocarbo onslowi) on Motuhinahina and Shag Rock were consistent with 2023 survey counts. Kopi Bush exhibited higher avian diversity than the smaller Motuhinahina (H=1.75 vs. H=1.07). Throughout Rēkohu, uncommon species such as feral greylag geese (Anser anser), feral chickens (Gallus gallus), kingfisher (Todiramphus sanctus vagans), and yellow hammer (Emberiza citrinella) were recorded in low numbers. Emu (Dromaius novaehollandiae) were also encountered, confirming their continued presence on the island. Our findings highlight the importance of continued monitoring to understand the changes in Rēkohu’s avifauna and provide valuable baseline data for future research and conservation efforts.