“A juvenile Common Myna (Acridotheres tristis) was documented snoozing on our parapet,” wrote Lakshmi Ravishankar.
Birds typically close their eyes when they sleep, but only one eye at a time (Gill, 2007). This allows them to be vigilant. According to Long (1998), the upper eyelids are used for blinking while the lower are pulled up during sleep.
In the case of the juvenile Common Myna, the lower eyelids of both eyes are pulled up together, but not for long. Apparently this type of sleep, termed rapid-movement sleep, common among mammals, is also seen in birds where it occurs in very short and frequent bouts. Among terns and swifts, such rapid-movement sleep is combined with “one-eyed” sleep, when they sleep on the wing.
Lakshmi Ravishankar
Pune, India
7th April 2018
References:
1. Gill, F. B., 2007. Ornithology. W. H. Freeman & Co., New York. 758 pp.
2. Long, K., 1998. Owls: A wildlife handbook. Johnson Books, Boulder. 181 pp.
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