Page 368 - AWSAR 2.0

344 || AWSAR Awarded Popular Science Stories - 2019
,Six different types of behaviours were then studied during the experiment, namely: a) Drowsiness: eye blink is frequently faster
b) Front Sleep: reduced frequency of eye blink c) Back Sleep: bird’s head
buried under the scapular
feathers and none of its eyes
are visible.
d) Uni-hemispheric Sleep: one
eye is closed and other eye is
open.
e) Alert Wakefulness: – eyes are
open, quick and frequent head
movements but no locomotor
activity.
f) Active Wakefulness: birds are
active and locomotor activity is
there
At the end of the
experiment after analysing our
video recordings, we found the
distribution of different sleep
postures across the night in
our birds. During non-migratory
(that is, under short days) and pre-migratory (that is, under long days, but the birds in this
stage do not show night-activity) life history states that the initiation of sleep is dominated by front sleep, back sleep and UHS. Mid-night phase was considered as the peak time for
sleeping as the birds spent most of their time sleeping in front sleep posture followed by back sleep. UHS was observed in dispersed pattern in very small bouts throughout the night. The late-night phase was also occupied by a substantial proportion of front and back sleep and again UHS was trivial.
In contrast, in the migratory phase (that is, under long days, but the birds show night activity) the sleep was restricted to early and late night phase with significant reduction in sleep quantity. This is because the birds had started showing migratory
restlessness and they took power naps either during early part the early night or late at
Graphical representation of the experiment design
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.