The effectiveness of point counts and mist-netting in surveying Afrotemperate forest bird community structure in South Africa

ABSTRACT

Point counts and mist-netting are two frequently employed survey techniques used in assessing forest avian communities, although the reliability of these methods varies according to species composition and habitat. This study investigates how effectively these two methods survey forest bird community structures within South African Afrotemperate forests. Seven forests within the Eastern Cape were surveyed from 140 duplicate point count and 63 mist-netting stations. Both methods were compared for assessing species richness, as determined from bird atlas data. Generalised linear mixed-effect modelling was used to determine functional traits which most impacted species detection, and to identify detection biases for both methods. Both methods compared consistently across the seven forests, which shared similar community structure. Point counts detected 79.2% of the total diversity versus 41.0% using mist-netting, and mixed-effects modelling corroborated that species detection is more effective using point counts. All functional traits tested (body size, primary foraging stratum, feeding guild, habitat specialisation, and dispersal behaviour) affected detection outcome. Point counts better represented all aspects forest bird community structure, including mid- and understorey birds which are presumed to be better detected by mist-netting. Use of mist-netting only slightly enhanced diversity assessments, and combined survey efforts under-represented forest-edge foragers, woodland and grassland habitat generalists (~63.6% total diversity), large birds, Palaearctic migrants, and carnivores.

KEYWORDS:

• Afrotemperate forest
• functional traits
• mist-netting
• point counts
• species detection

Acknowledgements

We would like to thank Welile Kedama of DAFF for permission to conduct fieldwork in Ngele, Gomo, Baziya, Manubi, and Kubusi state forests, ECPTA for permitting us to work in Fort Fordyce Nature Reserve, and SANParks for allowing us to work in Alexandria forest, in the Woody Cape section of Addo Elephant National Park. We would also like to thank Andrew Wannenburgh for creating the map in Figure 1. Finally, we would like to thank Julia Riley, James Baxter-Gilbert, and Daan Nel for assistance with GLM modelling.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics

Ethics clearance was approved by the University of Stellenbosch (#SU-ACUD16-00195). Permits were obtained for working in state forests managed by the South African Department of Agriculture, Forestry, and Fisheries (DAFF) in the Eastern Cape and Kwa-Zulu Natal, in reserves managed by the Eastern Cape Parks and Tourism Agency, and for Woody Cape SANParks Nature Reserve. Bird ringing was undertaken by J.M., licensed by SAfring, with permits for bird ringing in the Eastern Cape and Kwa-Zulu Natal (OP4487/2017).

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by grant 98871 from the Foundational Biodiversity Information Programme (FBIP) of the National Research Foundation (NRF) to MIC.