Turn out the lights: Does artificial light keep song birds up at night?

Source: Sun, J.; Raap, T.; Pinxten, R.; Eens, M. (2017). Artificial light at night affects sleep behavior differently in two closely related songbird species. Environmental Pollution, 231, 882-889. http://dx.doi.org/10.1016/j.envpol.2017.08.098


What is artificial light?

Artificial light at is unnatural light created by humans such as street lamps and vehicle headlights (Figure 1).  While it might not seem bright to you, artificial light can disrupt animal physiology (how the animal functions) and/or behavior.  For example, you may have heard that artificial light can deter sea turtles from laying their eggs on beaches.  How would you feel if someone shined a bright light in your face while you are trying to sleep?  The researchers in this study set out to find the answer to this question for two types of song birds.


Figure 1. Artificial light at night across America. Image Credit: NASA/GSFC/Craig Mayhew and Robert Simmon.


Test subjects: Great and Blue Tit Songbirds

In this study, the researchers examined how artificial light affects the sleeping behavior of two types of songbirds: Great Tit (Figure 2) and Blue Tit (Figure 3).  To do this, the researchers put out nest boxes and used cameras to monitor the sleeping behavior of both bird species in the nest boxes on two separate nights.  On one night an artificial light was placed in the nest box.  On the other night no light was placed in the nest box.  This experimental design allowed the researchers to compare the effect of artificial light on the sleeping behavior of the two different bird species.  The researchers were interested in examining sleeping behavior because it can represent brain activity, but is much easier to measure.

Figure 3. Blue Tit. Image Credit: Francis Franklin via Wikimedia Commons
Figure 2. Great Tits. Image Credit: Shirley Clarke via Wikimedia Commons.



The researchers determined that when the lights in the nest boxes were off, the sleeping behavior of the great and blue tits did not differ.  However, when the lights in the nest boxes were on, the great tits’ sleeping behavior was disrupted more than that of the blue tits.  The great tits fell asleep later, woke up earlier, left the nest box earlier, and lost more than 50 minutes of sleep when the light was on compared to when the light was off.  In contrast, the light only affected three parts of the blue tits’ sleeping behavior: they fell asleep later and had longer but less frequent sleeping periods.  The difference in responses to artificial light between the two species may be caused by differences in sensitivity, physiology, or ecological strategies.  It is interesting that even though these species are closely related, they respond differently to artificial light.  This means that we shouldn’t assume findings about one species can be applied to all species.



What’s next? 

In this study the birds were only exposed to artificial light for one night (short-term light exposure).  In reality, birds may be exposed to artificial light several nights in a row (long term exposure).  Future studies are needed to determine the effects of long-term artificial light exposure on these songbirds.  It is possible that long term exposure may be more disruptive to the birds, or the birds may habituate (become used to) the light exposure.

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Elizabeth Brannon

I recently graduated with a Ph.D. in Biology and Environmental Science from the University of Rhode Island where I studied greenhouse gas emissions from wastewater treatment. I am committed to developing a better understanding of the impacts we have as humans on the planet. I'm a hard core New England sports fan and when I'm not cheering on the Patriots you can find me outside on an adventure!

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