Ecological Archives --A1

B. Smit, C. T. Harding, P. A. R. Hockey, and A. E. McKechnie. 2013. Adaptive thermoregulation during summer in two populations of an arid-zone passerine. Ecology 94:1142–1154. http://dx.doi.org/10.1890/12-1511.1

Appendix A. Study species and study site information, including photographs and summary of weather recorded during the study.

Fig A1. A female White-browed Sparrow-Weaver (Plocepasser mahali) showing heat dissipation behavior (panting and slight wing-spreading). White-browed Sparrow-Weavers (35–50 g) breed co-operatively, living in family groups of 2–10 individuals, and occur in the arid savanna regions of southern and eastern Africa (du Plessis, 2005). These birds are omnivorous and feed on insects (80% of diet), seeds, and fruit (du Plessis, 2005). Family groups mostly occur far from free-standing water, and only individuals in territories surrounding a free-standing water source drink periodically (B. Smit, A. E. McKechnie, unpublished data). Photo credit: Ben Smit.

Fig. A2. Photographs taken during summer at (A) end of dry season and (B) wet season, at the semi-desert site, Tswalu Kalahari Reserve, and (C) at desert site, Wildsgenot Game Ranch. Mean annual rainfall is higher at semi-desert site than desert site, mainly because semi-desert site lies closer to the western boundaries of the inter-tropical-temperate troughs that bring predictable summer rain (Reason, Landman, and Tennant, 2006; Usman and Reason, 2004). Mean ± SD annual rainfall at semi-desert site was 295±172 mm (coefficient of variation, CV = 58.3%) over a 30-year period (unpublished data, Tswalu Kalahari Reserve). Mean ± SD annual rainfall at desert site was 190 ± 125 mm (CV = 66%) over a 60-year period (GHD Scholtz, unpublished data). The climate at the desert site is more extreme (both hotter by day and colder at night) and less humid than at the semi-desert site. The semi-desert site is located near the 33°C isotherm for mean daily maximum T_air during mid-summer, whereas the desert site lies beyond the 35°C isotherm where in some years mean daily maximum T_air can exceed 41°C for over a month at a time (South African Weather Service). Mean water vapor pressure deficit (measured at 14h00 each day in January) is typically 3–4 kPa at the semi-desert site compared to >4 kPa at the desert site (Schulze, 1997). Photo credit: Ben Smit.

Table A1. Weather during the study period at Tswalu Kalahari Reserve (semi-desert) and Wildsgenot Game Ranch (desert). Thermoregulatory data at the semi-desert site were collected during the dry summer (Period 1: Dec 2010) and wet summer (Period 2: Jan to Feb 2011), and at the desert site during the dry summer (Period 3: Nov to Dec 2011). Values represent mean ± standard deviation (range: minimum - maximum). Both ‘dry season’ data collection periods were at the end of typical annual dry cycles, which last from April to December, and neither site received any significant rainfall for at least seven months prior to the sampling periods.

* Mean measurements at 1400h

Literature cited

Reason, C. J. C., W. Landman, and W. Tennant. 2006. Seasonal to Decadal Prediction of Southern African Climate and Its Links with Variability of the Atlantic Ocean. Bulletin of the American Meteorological Society 87(7):941–955. doi:10.1175/BAMS-87-7-941

Schulze, R. E. 1997. South African Atlas of Agrohydrology and Climatology. Pretoria, South Africa.

Usman, M. T., and C. J. C. Reason. 2004. Dry spell frequencies and their variability over southern Africa. Climate Research 26:199–211.

du Plessis, M. A. 2005. White-browed Sparrow-Weaver. In P. A. R. Hockey, W. R. J. Dean, and P. G. Ryan, Editors. Roberts birds of southern Africa. Seventh Edition., pp. 1006–1007). Cape Town: The Trustees of the John Voelcker Bird Book Fund.

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