Page 367 - AWSAR 2.0

of this behaviour, thus the putative genes involved in the regulation of sleep are being vigorously investigated. Sleep is regulated by many biological factors, which coordinate in such a fashion that it forms a suitable environmental/physiological condition for an organism. Genetic studies have revealed that “period” and “cryptochrome” genes appear to be important for the modulation of sleep. Although sleep is characterized by a relative unconsciousness of the external world, the sleep cycle actually works through two major states found in both mammals and birds: non- rapid eye movement (NREM) and rapid eye movement (REM) sleep. During NREM sleep, breathing is slow, and our limbs and eyes are peacefully at rest. However, as we transition from NREM to REM sleep, breathing becomes fast and irregular, and our limbs twitch, and eyes dart around rapidly. In order to study this phenomenon, migratory finches, as birds, stand out to be unconventional, but excellent model to understand sleep. Many
species of birds are known to
migrate over long distances.
The effect of migration on
sleep has been studied in
various species of birds, which
includes swifts, sandpipers,
songbirds, and seabirds. It is
known that sleep loss adversely
affects the physiology of an
animal therefore, it is commonly
assumed that birds fulfil their
daily need for sleep even
during their flight. Birds have
a choice to switch between
sleeping with both hemispheres
or with one hemisphere (UHS – Uni-Hemisphere Sleep) depending upon the physiological and ecological demand. During UHS, the eye that is open is connected to the wake hemisphere and enables the bird to be aware of any kind of threat and helps it to control the movement during flight. UHS
Ms. Jyoti Tiwari || 343
hasbeenconfirmedinfrigatebirdsalsowhere the sleep is more asymmetric during flight as compared to that on land.
Birds like humans are diurnal in nature, so in our study we raised the question, whether during the migratory phase, birds sleep at night, as these birds are known to migrate during the dark hours. To test the effect of migration on sleep we, therefore, designed a simple experiment. Our study focused on the changes in sleep and sleep postures during non-migratory and migratory states of a night-migratory bird known as the redheaded bunting (Emberiza bruniceps). This bird follows the Palaearctic migratory route and belongs to the Emberizidae family. Also, though buntings are diurnal in nature, they switch to nocturnal mode of activity when exposed to migratory (that is, when given long photoperiod) conditions. These birds estimate the day length to regulate their reproductive cycle and migratory phenologies. This study was carried
out on male buntings where initially they were maintained in short photoperiodic condition (8L:16D, that is, 8 hours of light and 16 hours of darkness). Short photoperiod (8L:16D) maintains the non- migratory states whereas long photoperiod (13L:11D; 13 hours of light and 11 hours of darkness) is stimulatory, that triggers migratory phenology in these birds.
The birds were exposed to two different photoperiodic conditions: 8L:16D followed by 13L:11D. The activity/rest
pattern of the birds was recorded with the help of an infrared motion sensor, which detected movements inside the cage. Sleep was recorded by using cameras for the same birds for two successive nights.
Sleep is a universal behaviour that has been demonstrated in every animal species studied, from insects to mammals. An average human being spends roughly one-third of their lives sleeping, so undoubtedly this behaviour must be playing a significant role in keeping us fit and healthy.