Illuminating sleep in Black Swans
Anne Aulsebrook, The University of Melbourne, Australia
Are street lights keeping Black Swans awake?
Over the past 150 years, artificial light has dramatically transformed our night environment. Today, more than 80% of people live under skies that are unnaturally bright (Falchi et al. 2016). Furthermore, there is rapidly accumulating evidence that light at night can affect the behaviour, health, and reproduction of wildife, including birds (Dominoni and Nelson 2018).
The Black Swan population at Albert Park Lake, Melbourne (Australia) has been monitored by Professor Raoul Mulder and his research group for over ten years (Guay and Mulder 2009). The lake is near the central business district and is surrounded by roads, sports facilities, high rise buildings, and function centres, all of which are brightly lit at night (Figure 1). Research has shown that light is critical for regulating sleep in birds, as in other species (Rattenborg et al. 2005). The question that arises, then, is whether the disruption of natural light cycles affects the sleep of these swans.
In 2015, I began investigating the effects of street lights on sleep in urban birds, including Black Swans. My PhD research was supervised by Professor Raoul Mulder (The University of Melbourne), Dr Therésa Jones (The University of Melbourne), and Dr John Lesku (La Trobe University). As part of this research, we caught swans at Albert Park Lake and transported them to a wildlife sanctuary, which was naturally dark at night. There, we were able to experimentally test the impacts of street lights on swan sleep and activity patterns (Figure 2). The resulting paper is currently under peer review.
At the end of the project, we released the swans back at Albert Park Lake, and I have been able to track their behaviour since. Black Swans in our study population are tagged with plastic collars, so that researchers can identify individual swans from a distance (Figure 3). Members of the public can also submit their sightings of collared swans to a website and phone app, helping track the movements of these swans across the state (Mulder et al. 2010). Most swans that I studied are still at Albert Park, although a few moved across the bay, and one pair had cygnets while I was finishing my thesis.
Dominoni DM, Nelson RJ (2018) Artificial light at night as an environmental pollutant: An integrative approach across taxa, biological functions, and scientific disciplines. J Exp Zool A Ecol Integr Physiol 329, 387-393.
Falchi F, Cinzano P, Duriscoe D, Kyba CCM, Elvidge CD, Baugh K, Portnov BA, Rybnikova NA, Furgoni R (2016) The new world atlas of artificial night sky brightness. Science Advances 2, e1600377.
Guay PJ, Mulder RA (2009) Do neck-collars affect the behaviour and condition of black swans (Cygnus atratus)? Emu 109, 248-251.
Mulder RA, Guay P-J, Wilson M, Coulson G (2010) Citizen science: Recruiting residents for studies of tagged urban wildlife. Wildlife Research 37, 440-446.
Rattenborg NC, Obermeyer WH, Vacha E, Benca RM (2005) Acute effects of light and darkness on sleep in the pigeon (Columba livia). Physiology & Behaviour 84, 635-640.