Aspects of nocturnal physiology and behaviour in malachite sunbirds (Nectarina famosa).
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Date
2007
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Abstract
Although sleep forms an important part of an animal’s life, there is a paucity of knowledge
about sleep behaviour. The function of sleep in birds is poorly understood, even though
birds spend a large part of their lives sleeping. Sleep behaviour in passerine birds has not
been looked at as extensively as that of non-passerine birds. I looked at the sleep behaviour
of three relatively common passerine birds occurring in southern Africa, namely the
Malachite Sunbird (Nectarinia famosa), the Cape White-eye (Zosterops pallidus) and the
Fan-tailed Widowbird (Euplectes axillaris). By using an infra-red sensitive camera I
described basic sleep behaviours at various ambient temperatures, of all three species, such
as sleep position and eye closure, and also investigated the incidence of unihemispheric
sleep. Individuals of all three species spent most of the night asleep and kept on waking up
intermittently throughout the night, with no significant differences between temperatures.
Cape White-eyes and Malachite Sunbirds showed an increase in back sleep and a decrease
in front sleep at 5oC. Little evidence of unihemispheric sleep was found, suggesting that it
is more likely to occur in non-passerines, especially ground dwelling birds.
Diurnal birds generally sleep during the hours of darkness. Most male southern
African sunbirds have pectoral tufts, although the function of these is not always
understood. In male Malachite Sunbirds it has recently been found that they display their
pectoral tufts almost continuously throughout the night, whilst asleep. I explored the
possible function of this behaviour and suggest that these tufts might be a deterrent to
predators, as they look like ‘eyes’ in the dark. A review of the use and occurrence of
pectoral tufts in southern African sunbird species is also presented.
Blood glucose concentrations of most birds are much higher than those found in
mammals and it is still not known how they evade the complications of such high levels. I
investigated the change in blood glucose concentrations of Malachite Sunbirds at two
different ambient temperatures and at different times of the night and day and explored the
possibility that gluconeogenesis might be used by birds to ‘warm up’ during arousal of
torpor in the early morning, before daylight. Generally blood glucose levels were fairly
high, between 13.6 and 21.4 mmol/L, which was expected. Blood glucose levels were
higher at 5oC than at 25oC and generally lower in the early hours of the morning. Therefore
I reject the assumption that Malachite Sunbirds use gluconeogenesis as an additional form
of heat generation during torpor. It is thought that the difference in the levels of blood
glucose might be a function of the cold temperature and the consumption of their
nectarivorous diet.
This research clearly highlights the need for further studies to be undertaken in the
sleeping behaviours and patterns of birds, especially in southern African species. It also
shows that more studies need to be done on the use of pectoral tufts in sunbird species and
furthermore it is suggested that more research is needed to elucidate the mechanism by
which Malachite Sunbirds are able to rapidly ‘warm up’ during arousal, when in torpor.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.
Keywords
Sunbirds--Physiology--Africa, Southern., Sunbirds--Behaviour--Africa, Southern., Sleep behaviour in animals., Passeriformes--Behavior--Africa, Southern., Theses--Zoology.