Projecting present and future distributions of New Zealand’s sturnids: insights from ecological niche models

Kamolphat Atsawawaranunt^1*, Annabel Whibley¹ and Anna W. Santure¹

¹ School of Biological Sciences, University of Auckland, Building 110, 3 Symonds Street, Auckland 1010, New Zealand / Te Kura Mātauranga Koiora, Te Whare Wānanga o Tāmaki Makaurau, Aotearoa (kats326@aucklanduni.ac.nz, annabel.whibley@auckland.ac.nz, a.santure@auckland.ac.nz)

The common myna (Acridotheres tristis) and common starling (Sturnus vulgaris) are two of only three birds on the IUCN 100 Worst Invasive Alien Species list and both species are invasive in New Zealand. Understanding their current niches and any niche changes compared to their native range are key to predicting their future distributions, including areas for potential invasion. We used occurrence records from New Zealand and the native range and biologically justified environmental variables to build ecological niche models of the two sturnid species. We identified important environmental predictor variables for the species distribution and used these to project their present and future habitat suitability in New Zealand. The niches of the species in the native range and New Zealand were also compared to assess whether the species niche had changed. Growing degree days above 5°C was identified as the most important predictor for the myna distribution, with growing season length for the starling. Our future habitat suitability projections for mynas in New Zealand suggest increased suitable habitat areas towards the south, and into the North Island’s volcanic plateau. For starlings, future projections suggest increased suitable habitat at higher elevation in the Southern Alps. Our niche comparison analyses found no evidence of niche evolution between New Zealand and the native range, supporting a “home away from home” basis to their success in New Zealand. The habitat suitability projections can be used to help inform management practices, and the niche models can help inform future studies on the global species niche.

*PhD student