Persisting in a transformed landscape: occupancy and habitat association of the range-restricted Agulhas Long-billed Lark Certhilauda brevirostris

ABSTRACT

We investigated how the presence of the highly range-restricted Agulhas Long-billed Lark Certhilauda brevirostris (ALBL) varies with vegetation type and landscape features. The lark’s distribution is nearly completely outside formally protected areas and overlaps with a region where agriculture has transformed the landscape, with very little of the original vegetation type remaining. Establishing important habitat requirements is needed to better manage conservation efforts for the species. We conducted 10-minute point counts at 51 sites along small rural roads quarterly between October 2020 and January 2022, and recorded ALBL in 58% of the counts. A subset of 45 sites was used to model occupancy. According to a null constant parameter model, occupancy at sample sites was high (0.91) with a detection probability of 0.67 for each site where the species was present. Modelling of habitat features and vegetation type found that ALBL occupancy was best explained by the presence of renosterveld, the shrubby indigenous vegetation type. Occupancy increased at a site up to 25% renosterveld cover, after which there was no effect. Occupancy was also positively associated with renosterveld vegetation presence along fence lines and a combination of renosterveld and decreasing riverine vegetation cover. Presence was little modified by seasonal changes in agricultural land use. Overall, our results suggest that although the ALBL is locally abundant, certain habitat features need to be preserved to ensure the species’ continued presence in this agricultural region.

KEYWORDS:

• South Coast Renosterveld
• Overberg
• land use
• point count

Acknowledgements

Dr Odette Curtis-Scott and Grant Forbes from Overberg Research Conservation Trust provided invaluable field-based support. We thank the three anonymous reviewers for their constructive feedback which greatly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Information

Supplemental data for this article can be accessed at https://doi.org/10.1080/01584197.2024.2306376

Additional information

Funding

Funding for this study was provided by BTE Renewables (formerly BioTherm Energy)and the National Research Foundation.