![]() ![]() ![]() The physiological studies of sleep require extensive instrumentation including an electroencephlographic (EEG) machine to measure electrical activity of the brain, an electromyograph (EMG) to measure muscular activity and electrooculographic equipment (EOG) to measure eye movements. For example, the Echidna or spiny anteater, a primitive mammal from Australia, exhibits all the behavior of an outstanding sleeper and adapts well to the laboratory but unlike other mammals studied, the Echidna does not dream. Behavioral observations re very difficult to interpret as an animal may exhibit a certain behavior, but not necessarily the associated physiology. Behaviorally a bird would be expected to return to a specific site, exhibit a specific posturing, and have an increased arousal threshold. Sleep can be defined both behaviorally and physiologically. Some birds may do all these things, but each is done separately. Words such as torpor, hibernation, resting and sleep are not interchangeable. So is it true that birds sleep' To answer the question "Do birds sleep'" requires specific terminology. In fact, the need for sleep in some animals and humans is so strong that prolonged deprivation has caused irreversible behavioral changes and, in some cases, death. ![]() However, sleep is a powerful and definable physiological state. I then realized how frequently, both in film and literature, people speak of birds sleeping. In fact, the robin is the most common night-time songster in Britain's towns and gardens.I was recently watching a film about the European kingfisher which showed a perching kingfisher and the narrator stated the bird was sleeping. This has resulted in dozens of reports of nightingales singing in the middle of the winters night and other equally unlikely times and places, which have all turned out to be robins. Since robins keep territories all year round, they also sing all round the year. ![]() With this tendency to be active at low light, robins can be easily triggered into full song by a streetlight or any kind of floodlighting. They are one of the earliest birds to start the dawn chorus and one of the last to stop singing at night. Robins are insectivorous birds that are well adapted to foraging in dim light, and even continue to feed under artificial light well into the night. This is indeed what often happens with song thrushes and dunnocks, and doubtless many other species, but the unrivalled kings as daytime birds turned night-time songsters are robins. The effect of dim lightīecause even low light intensities can trigger song in some birds, and because they continue singing until the last rays of light have faded in the evening, it is easy to see how the singing period could easily be extended into the night. It is thought that dawn chorus happens because birds wake up before there is enough light for them to feed and so they focus on singing instead. A very similar order, but in reverse, follows the sunset. The dawn chorus is normally started by the robin and the redstart, with sparrows and many finches being the last to join in. Onset of song in the morning, the dawn chorus, is triggered by a combination of the birds internal clock and the very first rays of light. As well as the true nocturnal species, reed and sedge warblers among others, sing extensively during the night.Īll birds, whether diurnal or nocturnal, are governed by the daily rhythm of light and dark. Apart from owls, our other nocturnal songsters, corncrakes, nightjars and nightingales are all migratory birds with a short and well defined song period during the spring and summer months. ![]()
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