The conservation of the short clawed-lark : Certhilauda chuana

Abstract

The Southern African endemic Short-clawed Lark Certhilauda chuana comprises two geographically isolated populations, consisting of a western and an eastern population. Several authors have suggested that the taxonomic status of the eastern population be verified. In an attempt to resolve the taxonomic uncertainty regarding the two populations, DNA molecular data was used in a comparative study of the two populations. The DNA sequence data was generated using standard methods of DNA extraction, PCR and automated DNA sequencing for partial sequences of the mitochondrial genes Cytochrome b and ND2. A total of 530 base pairs of the Cytochrome b gene were amplified for individuals representing both Short-clawed Lark populations. The results obtained from the amplified Cyt b sequences showed the populations to be identical. The amplified partial ND2 gene (972 base pairs) showed sequence divergence between the eastern and western populations ranging between 0.10 - 0.31%. The partial ND2 gene produced only four haplotypes for both the eastern and western individuals with a single mutational step separating each of the haplotypes. The results of the DNA analysis showed that there exists very little genetic diversity within and between the two populations. Confirmation of the taxonomic status of the two populations was supplemented by comparing selected morphometric measurements and territorial song characterization. Apart from a statistically significant difference (P < 0.05) in the length of the tarsus, there were no other significant differences in the morphometric parameters analysed. A comparison of the territorial calls of males showed considerable individual variation between males within a population and statistically significant differences between males from the two populations for some of the parameters analysed. v The results of a habitat preference study for the eastern population was determined by analysis of the micro- and macro-habitat features within presently and historically occupied territories. It was established that as with the western population, Short-clawed Larks from the eastern population also show a fine-scale habitat preference within the broad, general habitat description of “open habitat, sparsely vegetated with small trees and shrubs”. The results of the present study explain the highly localized distribution of the species within its area of occurrence. The results also suggest that the species’ habitat preference is probably dictated as much by physiological requirements, e.g. short-grassed areas with bare ground for breeding and foraging, as it is by behavioural requirements, e.g. large open areas for aerial displays and small trees or shrubs for territorial calls. In addition to the above, surveys were conducted to determine the species’ present extent of occurrence, area of occupancy and to obtain population size estimates. The results were compared with published data from the Southern African Bird Atlas Project and showed a dramatic range reduction of this species. Possible reasons for the range reduction include habitat loss, absence of formally protected habitat and altered ecological processes such as lack of fire and bush encroachment. It is estimated that the eastern population of the species comprise fewer than 380 breeding pairs. The observed range reduction and estimated population size suggests that the eastern population of the species requires urgent protection. A comprehensive investigation of Short-clawed Lark vocalisations and displays was conducted. This study presents the first detailed analysis of the vocalisations of the Short-clawed Lark. Analysis of call data showed considerable variation in the number and placement of pulsed and whistle notes in their different calls. The extent of individual variation within the eastern population for the parameters analyzed, failed to reveal any dialects associated with the vocalisations of Short-clawed Larks from the eastern population. Although Short-clawed Larks call and display throughout the year and during most parts of the day, most vocalisations and displays peak in the first 1-3 hours after sunrise in the peak-breeding season. This information is useful for identification and monitoring purposes. This manuscript concludes with a discussion of the major threats facing the population, recommendations on how to address them, and conservation priorities for the eastern population and the species.