I don’t know anything about the mechanisms behind “sleep”, but I have seen some striking alternative strategies to the “sleep” strategy used by humans. It is intuitive that whales and dolphins do not “sleep” the same way we do, because they have to keep swimming their entire lives. Some rest at the water surface occasionally, but most never do. Sperm whales show a behaviour pattern none as “logging” in which they lie at the surface for half an hour or so, breathing. Perhaps they are asleep. Baleen whales show a pattern also termed “logging” where they move slowly and steadily in a straight line with fairly constant timing in the breathing and diving sequence. It is not unusual to see them suddenly “wake” from this pattern when confronted with an obstacle such as a boat. I once saw a fin whale surfacing under a massive floating log once only to wake suddenly and make some last minute and energetic manoeuvres to avoid collision, and then go back to logging. They also spontaneously “awake” and go into less automated and more diverse behaviour patterns. A Christmas Island Frigatebird that we satellite-tracked in 2006 flew about 5,000 km in 27 days without landing. Altimeter loggers on Great Frigatebirds have shown that they spend more than 50% of the time “at sea” soaring in thermals under cumulus clouds thousands of metres above sea and land. Their wings would lock in place but they would still need to sense and steer to remain in the thermal. Yet frigatebirds do appear to sleep on the nest, often with the head and neck hanging vertically below the nest, eyes firmly shut, and totally oblivious to noise such as ecologists counting nests, yelling to one another, etc. Frigatebirds and whales might use “unihemispherical sleep” but I doubt that it would be the same thing in the two groups, since their evolutionary histories are are so different. And how would a storm-petrel sleep in a 10-day gale in the southern ocean? This would surely require staying fully awake for however long was necessary. Semantically, either only humans “sleep” like humans do, or “sleep” has many forms and humans only experience one.
David James, Sydney burunglaut07@yahoo.com ==============================
From: Andrew Taylor
On Mon, Sep 05, 2011 at 07:22:52AM -0500, Chris Corben wrote: > A couple of points arise from this. Firstly, I have never seen any > evidence of Frogmouths sleeping. As far as I can tell, they are > always awake and alert. I have watched them under a great variety of > circumstances both in the wild and in captivity, and I have never > seen one which seemed asleep. > I have seen plenty of other birds which appeared to be asleep and > were clearly unaware of things going on around them. But I don’t > know what sleep means to a bird, and if there is a range of states > which they can be in, or how different groups of birds vary in this > respect.
It seems we are just getting answers to these sort of questions.
Unihemispheric slow wave sleep with half the brain asleep and one eye closed is known from some bird species, and individuals on the exposed periphery of roosting flocks have been observed to enter this state more, presumably because they are at greater risk of predation.
This very recent paper titled “Ostriches Sleep like Platypus”: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0023203 found Ostriches enter a slow wave sleep state with both eyes open and look alert but motionless. Ostriches also enter a both eyes-closed REM sleep state similar to human.
So a motionless Frogmouth with eyes wide open might be asleep.
Its speculated species which spend days aloft such as swifts could enter slow wave sleep on the wing. EEGs might be still too cumbersome for swifts but they are definitely small enough to put on a Frigatebird so we should know more soon.
Frogmouths are also known to allow their body temperature to drop and enter shallow torpor for several hours during the night or early morning. I haven’t seen it reported for Frogmouths but other birds which enter torpor may have eyes open or closed.
Andrew
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
http://birding-aus.org =============================== ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
