watchful sleeping

[joe <jdaniel@aristotle.net>]

The May issue of Scientific American had a small article on the ability
of birds to kep one eye open while asleep. They also let half of their
brain sleep during this time, known as unihemispheric sleeping.
Experiements on ducks demonstrated that they have control over which
side of the brain is sleeping at a time. One side slept while the other
side stayed on guard. The article actually made a big deal of this
watchfulness of the awake side, with the quoted scientists saying it
probably developed to guard against predators, a sensible notion. They
suggested that mammals didn't develop this behavior because early
mammals likely slept in safe burrows. Recent work has also shown that
some lizards can do this indicating that "this sleeping state may have
been shared by an early ancestor." Does anyone know if any current
archosaurs do this? How common is this abilty in other reptiles? Is it
known if all birds do this? It would be reasonable to expect that this
behavior was common in dinosaurs, yes? Or at least in the lineages
closely related to birds?

Joe Daniel