Abstract
Competition occurs when individuals or different species are vying for the same resource which is in limited supply. Two complete competitors cannot coexist indefinitely, therefore competitors must differ to some degree in their resource use. The research was carried to investigate how resources are partitioned among the species of sunbirds found in Federal College of Forestry, Jos. Opportunistic sightings along a 200m transect was used for observation. Sunbirds were observed using binoculars between 6:30 – 8am and by 4:30 – 6pm. Six transects were purposively selected in the study area. Sightings along a 200m transect was used to observe; species of sunbird, sex of individual sunbird species, species of flowering plant visited by the sunbird species, activity or behaviour performed by the sunbird (probing, insect hunting, roosting, perching etc.) and duration of activity. Descriptive statistics, ANOVA and post hoc test was used to analyse the data obtained. Results showed that forty-three (43) plant species were utilised by the four (4) sunbird species found in the study site with Corymbia torelliana and Hamelia patens having the highest number of visit. These four sunbird species observed were; Scarlet-chested sunbird, Variable sunbird, Green-headed sunbird and the Copper sunbird. Mean number of plants visited shows that Green-headed sunbird visited more plants than the other three species (28.89) which was highly significant (p=0.001). Copper sunbird spent the highest foraging time (67.71) which showed no variation with the other species (p=0.516). Females of the sunbird species visit more plants species and spent more time foraging as compared to the males although there was no variation (p= 0.984 and p= 0.906 respectively). The activities of the males (perching, hovering, probing, feeding) was higher than that of females and had a high level of significance (p=0.001). Callistemon citrinus, Corymbia torelliana, Eucalyptus camaldulensis, Hamelia patens, Parkia biglobosa and Ziziphus mucronata were utilised by all the sunbird species. Scarlet-chested sunbirds spent more time probing which aids pollination of plants in the study site and hence ecologically important to the plants found in the study site.
Highlights
The coexistence of sympatric species is made possible by the differential utilisation of resources and niches (Fossette et al, 2017)
Hamelia patens had the highest visitation rate, Variable sunbird had the highest frequency of visit (112) to Hamelia patens while Green-headed sunbird has its highest visit to Spathodea campanulata and Scarlet-chested has its highest visit to Coryambia terolliana (90 and 130 respectively).Only six (6) plant species were visited by all the sunbird species found in the study site which includes; Callistemon citrinus, Corymbia torelliana, Eucalyptus camaldulensis, Parkia biglobosa, Hamelia patens and Ziziphus mucronata
The sunbirds visited different plant species or the same plants at the same time interval by utilizing different parts of the plants, sometimes if a particular species is probing for nectar the other species will be seen perching on other parts of the tree, which indicates that some species can coexist by having different niches on a particular food resource which must not overlap to avoid competition, as it was observed that copper sunbird and variable sunbird visited Hamelia patens same time but while the copper probe the variable sunbird perches or hover around it
Summary
The coexistence of sympatric species is made possible by the differential utilisation of resources and niches (Fossette et al, 2017). Coexistence of sympatric bird species can be made possible by the partitioning of a shared habitat (Carstensen et al, 2011), the type of resource used (Beaulieu and Sockman, 2012), foraging strategy employed (Oyugi et al, 2012) or specialisation on a particular resource (Craig, 1990). Resource partitioning can result from three pressures, competition, predation and physiological constraints (Toft, 1985) and the outcome is an alleviation of the pressures of competition. If two species occupy the same ecological niche, one would eventually dominate, out-competing the weaker competitor (Griffin and Silliman, 2011). The negative effects of interspecific competition may be mitigated by species reducing the degree of overlap in their ecological niches and using resources in different ways (Ricklefs, 2007)
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