International Journal of Molecular Evolution and Biodiversity 2016, Vol.6, No.3, 1-8
6
Figure 3c Pattern of visitation over time for
Callistemon
Figure 3d Pattern of visitation over time for
Lilium
3.2 Behavioural patterns
Of the behavioural data collected, a notable pattern was observed for feeding and perching; the proportion of visits
for perching and feeding differed significantly (
Chi-Sq
= 7.988,
df
= 3,
P
=0.046). At all time period sunbirds of all
species at all plants were largely feeding and the majority of visits involved probing for nectar.
4 Discussion
In this study, we found evidence for partitioning of visitation to four sympatric plants with sunbird species visiting
between one and four of our focal plant species and exhibiting temporal trends. This might be due to intense
competition among flower visiting sunbirds, variation in availability of nectar and difference in feeding and flower
characteristics. However Brown and Brown (1979), had observed non selective foraging and visitation by all
humming bird species to all nine flowing plant species in White Mountains of Arizona, due to their similar
appearance and nectar rewards. A total of 8 species of sunbirds were recorded visiting the focal plant species. The
Olive-bellied sunbird was the most common visitor, and was the only species to visit all four plant species,
suggesting a very generalist feeding habit. The Green-throated sunbird was the only one which restricted its visits to
flowers of only one species (
Spathodea
). The reason for this might be due to their feeding characteristics in which
this sunbird visits this particular plant only to forage for supplementary food; in conformity with Fry et al. (2000),
who found that Green-throated sunbirds mostly favour insects over nectar as a primary source of food. Or due its
morphological details of its bill and flower which influences its foraging success (Gill and Wolf, 1978).
Seven out of the eight species of sunbirds visited
Erythrina
and
Callistemon
while six and two sunbird species
visited
Spathodea
and
Lilium
respectively. This could be due to the ease of nectar accessibility from the former
species as well as the quantity of nectar produced and stored in their flower. In the other two plants, the nectar is
either not easy to access or there is low amount of nectar produced by the flower. This can be related to the work of
(Vogel, 1954 cited in Wilmer, 2011), which states that different floral structures attract different types of bird
visitors. For example; narrow-tubular and brush flowers normally attract small birds with long beaks and tongues.
Wilmer (2011) stated that across nectar producing plants, the amount or volume of nectar is abundant in some
plants and low in others, which makes a difference in the rate of visitation.
The rate of visitation per hour per flower was not consistent in all the focal plants and this may also reflect nectar
availability at different times of the day. Total flower visitation for all sunbirds to our focal plants across all time
intervals showed no significance difference, but clear patterns in visitation over time were evident within plant
species. Activity of sunbirds on flowers was highest early in the morning in both
Erythrina
and
Callistemon
; the
subsequent decline may be because these species do not replenish nectar later in the day. The same is true in Frost
and Frost (1980), where feeding activity was higher in the morning due to high nectar availability. In contrast, a
mid-day peak in visitation for
Spathodea
and
Lilium
suggests that these plants may have continuous nectar secretion
during the day. This is supported by Bibby et al. (1992), who stated that birds are more active during early morning
and late in the afternoon.
