International Journal of Molecular Evolution and Biodiversity 2016, Vol.6, No.3, 1-8
7
In
Erithrina
, visitation by Green-headed sunbirds increases as the morning progresses, whereas, Olive-bellied and
Collared sunbird visitations begin to drop at the same time. This could be explained by the fact that during our
observations, Green-headed sunbirds were highly territorial, chasing all other sunbirds while they approach to
access food. And it has higher visitation rate to all our focal plants than the other seven sunbirds. This might be due
their high energy demand as a result of competitive behaviour. Territoriality behaviour in male Golden-winged
sunbirds in Kenaya, allows then to forage 72%more each than nonterritorial ones (Gill and Wolf, 1979), to maintain
the energy balance (Gill, 1978). Additionally, the activity of Olive-bellied sunbirds is high during the mid-day in all
focal plant species whereas the other sunbirds become less active. This indicates that the Olive-bellied sunbird may
be less competitive, switching its foraging preferences, so it avoids competition from other sunbird species by
foraging when the activity of the others decreased.
Feeding and perching activities, when compared with total visitation revealed that most of the visitors came to
forage for nectar on our focal plants; thus potentially allowing pollination to take place. This supports the statement
by (Waser and Ollerton, 2006 cited in Wilmer, 2011) that pollination is primarily an animal-mediated phenomenon,
and that birds are recognized as very active pollinators of plants (Laubhann and Puff, 2002); hence in this instance
sunbirds, constantly arrived to feed on nectar and (Fanshawe and Stevenson, 2002 cited in Wilmer, 2011).
Overall, our study produced patterns of visitation in all focal plant species by the eight sunbird species which
suggests that some partitioning of visitation occurs between species and over time of day. There are aspects of
nectar resource availability, together with competition and/or territoriality that require further investigation to
discover the factors influencing interactions between co-occurring sunbirds and sympatric plant species competing
for pollination services. Further studies might also involve investigating variation in pollen placement on visiting
birds, an initial part of our preliminary discussions for this project, and plant reproductive success through
pollinator efficiency measures. The relationship between visitor behaviour and plant morphology can provide
information on increasingly specialized mutualisms and the drivers of evolutionary change.
Author’s contributions
All authors have designed and conducted the data collection and together undertake the data analysis task. In addition, all authors
read and approved the final manuscript.
Acknowledgment
We would like to express our heartfelt gratitude to Tropical Biology Association (TBA) for the golden opportunity of attending this
course. Also, many thanks go to Dr Nigel Mann and Dr Bruce Anderson for their unreserved assistance during the field observation
and their supervision. Our deepest appreciation goes to Dr Clive Nuttman for his continuous follow-up and genuine support
throughout our project.
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