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Environmental correlates of Freckled Nightjar (Caprimulgus tristigma) activity in a seasonal, subtropical habitat

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Abstract

We examined environmental correlates of activity in the Freckled Nightjar (Caprimulgus tristigma), a nocturnal aerial insectivore that is resident year-round in the colder and drier parts of southern Africa. Specifically, we tested the prediction that air temperature (T a), in addition to light availability, is a significant correlate of Freckled Nightjar activity. We found that aerial insect density varied by over three orders of magnitude (from <1.0 to 117.1 insects 1,000 m−3) during the course of the study, and was strongly and positively related to T a. Nightjar activity was also significantly temperature-dependent, with a cessation of activity at T a < 12°C. Consistent with previous studies, we found that activity levels were strongly related to ambient light, with markedly reduced activity levels on dark nights. The average number of Freckled Nightjars encountered per 14.6-km transect was 1.95 ± 2.44 nightjars transect−1 during nights near full moon, but only 0.17 ± 0.61 nightjars transect−1 around new moon. Our study reveals that caprimulgid activity can be significantly influenced by temperature as well as ambient light.

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Acknowledgments

We sincerely thank Alecia Kirton for her invaluable statistical advice, and Richard Newbery, Idah Mathe, Linda Marcus and the rest of the staff of Kgaswane Mountain Reserve for their support. Our thanks also go to Nikki Fisher, Tony Ashdown, Kay Fisher, Justin Phama, Gareth Borman, and Hlengiwe Mbatha. Tom Rogers of Lynx Optics, Johannesburg, kindly provided discounted spotlighting equipment. Mark Brigham provided helpful advice and insightful comments on the manuscript, and we benefited greatly from discussions with Walter Jetz and Marcus Byrne. This project was facilitated by funding from the University of the Witwatersrand (Friedel Sellschop Award) and the DST/NRF Centre of Excellence at the Percy Fitzpatrick institute to A.E.M. All procedures were approved by the University of the Witwatersrand Animal Ethics Screening Committee and comply with current South African laws.

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Authors and Affiliations

  1. DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits, Johannesburg, 2050, South Africa

    Robert A. M. Ashdown & Andrew E. McKechnie

  2. Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa

    Andrew E. McKechnie

Authors
  1. Robert A. M. Ashdown
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  2. Andrew E. McKechnie
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Correspondence to Andrew E. McKechnie.

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Communicated by T. Friedl.

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Ashdown, R.A.M., McKechnie, A.E. Environmental correlates of Freckled Nightjar (Caprimulgus tristigma) activity in a seasonal, subtropical habitat. J Ornithol 149, 615–619 (2008). https://doi.org/10.1007/s10336-008-0309-7

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  • DOI: https://doi.org/10.1007/s10336-008-0309-7

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