Frugivorous bird species diversity in relation to the diversity of fruit tree species in reserved and designated green areas in the federal capital territory, Nigeria

Abstract

The diversity of frugivorous bird species in relation to tree species diversity was investigated in Designated and Reserved Green Areas of Abuja, Nigeria. The study estimated, investigated and examined trees species and avian frugivore in terms of their diversity. Point-Centered Quarter Method (PCQM) was used for vegetation analysis while random walk and focal observation was used for bird frugivore identification and enumeration. data was collected from six locations coinciding with the local administrative areas within the Federal Capital Territory. These were, the Abuja Municipal Area Council (AMAC), Abaji, Bwari, Gwagwalada, Kuje and Kwali. AMAC is designated as urban while the remaining five sites are designated as sub-urban. The highest number of fruit tree species was encountered in AMAC (30), followed by Abaji (29) while 27, 25, 19 and 11 fruit tree species were encountered in Kwali, Bwari Gwagwalada and Kuje respectively. The similarity or otherwise dissimilarity in fruit tree species composition between each pair of the enumerated sites showed Gwagwalada and Kuje as the most similar, and the similarity or otherwise dissimilarity in frugivorous bird species composition between each pair of the enumerated showed higher species similarity between the AMAC and each of the other sites, and between each pair of the sites than that of the fruit trees in the respective sites. Highest number of frugivore bird species was encountered in Kwali (41), followed by Bwari (39) and AMAC (38) while 35, 34 and 21 species were encountered in Gwagwalada, Kuje and Abaji respectively. The alpha (within-site) diversity of frugivore bird species at different sites using Simpson and Shannon-Wiener diversity indices showed that Gwagwalada is the most diverse of all the sites, followed by Kuje and Kwali respectively. The diversity indices of frugivores and fruit-trees were correlated, a weak relationship was observed (r= - 0.2323 and r = - 0.1626), and Null hypothesis was accepted. Also, ANOVA was carried out to test for significance between the sites and the tree physical structure parameters. The result showed no significant difference between the sites (F_cal=0.236603 and F _Crit =2.901295), and the null hypotheses was accepted. Again, there was significant differences between the tree physical structure parameters (F_cal=20.58803 and F _Crit =3.287382), the null hypothesis was rejected. It was therefore concluded that these reserved areas need more protection to enhance both the beta and alpha diversities in order to support more interactions.

Keywords: Frugivores, Fruit trees, Diversity, Interaction, Green Areas, Urban ecosystems