International Journal of Molecular Evolution and Biodiversity 2016, Vol.6, No.3, 1-8
2
flower. Plants may also invest more into floral structures in order to attract one particular bird visitor more than
another (Stiles, 1978, cited in Wilmer, 2011). Thus it has been observed that, different floral structures attract
different types of bird visitors (Vogel, 1954 cited in Wilmer, 2011). For example; narrow-tubular and brush
flowers normally attract small birds with long beaks and tongues.
Competition is an interaction that may occur between individuals or species surviving on the same limited
resource (energy, nutrients and space) (Gill, 1978). Competition can either be interspecific (between species) or
intraspecific (within species). The principle that similar organism requires similar niche makes competition
evident. Sunbirds are no exception to this; hence in the event of competition, different species device different
means or strategy to cope with competition for limiting resources. Lara et al. (2015) reported that “species show a
differential use of resources in the face of interspecific competition as a fundamental manner of achieving species
coexistence” (Hutchinson, 1961; Schoener, 1974; Pyke, 1982). In order for some species to avoid or limit
competition they often rely on resource partitioning; hence, this can be explained in both space and time.
Variation in floral types is the basis of the concept of pollination syndromes. This implies that different kinds of
plants attract different visitors, cementing the mutualism and by implication, tend to make flowers increasingly
specialist, and visitors increasingly selective (Wilmer, 2011). Characteristics of ornithophilous flower species are
described as: (i) red corolla or calyces or bracts of spikes; (ii) long stout corolla tube; (iii) tightly imbricate spikes
with stout long peduncle; (iv) high nectar production rate; and (v) low sugar concentration of floral nectar (Kato et
al., 1993). Selection of plant species for this study was guided by principles (i), (ii) and (iii) above. Thus, in this
study, we selected four plant species (
Erythrina
sp
.
,
Lilium
sp.,
Callistemon citrinus
and
Spathodea campanulata
)
growing sympatrically in Kibale National Park, Uganda.The study investigated sunbirds visitation (species type,
frequency and rate) to four sympatric plant species and partitioning of visitation over time of the day was also
examined.
2 Materials and Methods
Materials which were used during our field work was; Binoculars, field note book, timer (wristwatch) and pen etc.
2.1 Study area
This study site is located in Kibale National Park, in western Uganda closed to the equatorial region. The Kibale
National Park covers an area of 766 km
2
with geographical coordinates: 0
ʹ
13ʹ-41ʹN, 30
°
19ʹ-30
°
32ʹ E. Kibale forest
area was gazetted as a National Park in 1993 (Figure 1). The moist evergreen forest is transitional between
lowland rain forest and montane forest (Chapman and Chapman, 1997).
Figure 1 Study area location
