Thermoregulation and microhabitat use by Dune Larks in the Namib Sand Sea

Dune Larks are the only birds to live permanently in the Namib Sand Sea. Their restricted range makes it Namibia’s only fully endemic bird species. Like most desert animals Dune Larks save both water and energy by limiting their activity to the early morning and late afternoon periods and relying heavily on passive cooling methods, such as seeking shade and drooping their wings to allow the wind to flow under them. They escape the heat of the day by resting under the thin dune vegetation. However, small endothermic animals, like Dune Larks, lose about 5% of their body mass every night maintaining their body heat and they need to recover mass again the next day. If it is too hot, the birds forfeit their foraging time to stay in the shade, resting and when conditions remain hot for several days consecutively, a bird’s overall daily mass change (day-night) can fall to or below zero for too long. This can affect its overall health and breeding success, and even the growth and success of its chicks.

My master’s project aims to understand how Dune Larks cope with living in the Namib. I am particularly interested at what temperature they forfeit foraging to rest in the shade, and at what temperature this behaviour causes negative daily mass change. I will use these threshold temperatures to model the likely future distribution of Dune Larks, based on current climate change predictions.

To achieve this understanding my project has three parts. Firstly behavioural observations taking special note of any heat stress behaviour, such as panting, wing drooping, or shade seeking as the day progresses. Secondly mapping the vegetation cover providing possible micro-habitats to the birds to mitigate the heat of the day and observing which habitats they use. The final task of my project is to calculate daily changes in bird mass. Using a small population who has been habituated to land on a scale in exchange for food, allowing me to monitor their mass. I can then determine at what point heat stress affects the overall body condition of the bird.

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