Making the best of a Human modified Habitat; an Assessment of Avian Distribution and Diversity in Federal College of Education (Technical) Gombe. Gombe State- Nigeria

We assessed the abundance and diversity of avian species in two distinct habitats types; main campus area (human inhabited) and adjoining heavily degraded savannah grassland. By employing Jaccard/Tanimoto Coefficient of Similarity, we tested whether bird species assemblage will differ between the two habitats, while Shannon Weiner Diversity Index was used to determine the level of diversity between sites. Line transect assessment generated a total of 1035 individuals of 69 avian species from 53 genera and 32 families. The most diverse avian family was Estrildidae with nine (9) avian species, followed by Columbidae with six (6), while Falconidae, Nectriniidae, and Turdidae families had a record of four (4) species each. Five families (Ardeidae, Malaconotidae, Ploceidae, Silviidae, Sturnidae) and five families (Accipitridae, Bucerotidae, Capitonidae, Viduidaeand Psittacidae) followed with three (3) and (2) species respectively. Seventeen (17) families were each represented by a single species. Jaccard/Tanimoto Coefficient revealed that species composition differed between the two habitats with a similarity coefficient of 66.7 %, while Shannon Weiner Diversity Index was 1.56 and 1.67 for human inhabited (HI) and degraded savannah (DS) habitats respectively. The proximity to a natural savannah habitat albeit degraded has positive implications for avian diversity in the study area. We recommend more exclusion of human activities such as fuel wood harvesting and land grab for farming as this has grave consequences for the thriving population of species that are sensitive to human presence and urbanization. Keywords— Avian species, Diversity, Habitat utilization, Disturbance. Abundance.

Birds reflect changes in other biodiversity (examp le other animals and plants) and are highly responsive to environmental perturbations; making them very useful in studies designed to address the effects of human and other environmental disturbances on community stability and ecosystem productivity (Ezealor, 2002;Gregory et al., 2009). Birds contribute substantially to the overall species richness of West African forests, currently recognized as biodiversity hotspots of global importance (Orme et al., 2005). Species diversity is a co mmun ity attribute that is directly related to ecosystem p roductivity and vegetation structure (Tilman, 1996). Research has shown that species diversity is directly lin ked with habitat structure (James and Warner, 1982) as well as patterns of distribution of resources within a given ecological setting (Pringle et al., 2010). The pattern and distribution of species has serious implication for co mmunity productivity. For instance, Pringle et al. (2010) p roved that the regular (even spacing) spatial pattern of termite mounds found in a ho mogeneous African savannah provided a guide for parallel spatial patterning in tree-dwelling, termite-eating animal communit ies. Their findings, which also confirm that the uniformity of these patterns at small spatial scales boosted productivity of the whole landscape; provide support for models linking spatial patterns with ecosystem processes and functioning (Memmott et al, 2004;Bakam et al., 2018). In the same manner, we exp lored how habitat structure and resource availability in a human mod ified habitat will affect avian distribution, abundance and diversity (Odewumi et al., 2017). We tested whether species will partition resource use along a gradient of disturbance in the study area . This was possible considering the fact that the campus is contiguous to a natural but patchy and degraded savannah landscape made of some remnant native tree species. Our experimental approach was guided by the fact that vegetation structure is the most proximate factor that determines the spatial distribution of species (James and Warner, 1982); and more specifically bird diversity, enhanced by the plant species composition Manu et al., 2010). The goal of this study was therefore to determine how well birds utilize hu man modified habitats as well as the factors that may be crucial for their persistence in this degraded landscape. Specific objectives were to; i.
Develop a comprehensive checklist of the area. ii.
Identify the most abundant species in the study area iii. Determine whether species composition (diversity) will differ between the two sites.  The college lies within the Sudano-Sahelian Savannah vegetation typified by shrubs and sparsely distributed tree species. Regrettably, as is typical with most human modified habitats, the campus flora is now dominated by exotic and introduced tree species interspersed with a few remnant natives, the most prominent being Parkia biglobosa and Tamarindus indica. The college is divided into two unique habitats; the campus area hereinafter referred to as the human inhabited (HI) contiguous to a degraded savannah (DS) (Fig  1). The most common native tree species in the degraded savannah habitat was Parkia biglobosa while Azadaricta indica (Neem) was the most co mmon tree species in the human occupied habitat.

Experimental Design
Line transect method (Bibly et al, 2000) was used to estimate and record bird species seen or heard within the study area. The campus was divided into two major habitat types; Degraded Savannah (DS) and Human inhabited (HI), with each habitat comprising of three transects. Each transect was located at a horizontal distance of 250 m apart to ensure that the same bird species was not recorded repeatedly in a given transect. Each transect covered a total distance of 2000 meters. Transects were monitored twice each day in the mo rning and later in the evening. The mo rning session commenced at 6:30 am and lasted till about 9:30 am, wh ile the evening sessions were conducted between the hours of 3:30 p m -6:30 p m. During each transect survey we walked slowly along each transect and recorded bird species seen at least 50 m on either side of the transect or heard (Bibly et al, 2000). With the help of a pair of (Nikon sporter ® 8 x 42) binoculars we recorded the number seen and estimated the distance away fro m the transect. Each transect was repeated twice to optimize the record. The survey was conducted in 2016 during the end of the dry season and towards the onset of the rains . Data generated fro m the survey was entered in excel spreadsheet version 2013 and exp lored before exporting same to SPSS. The statistical Package for Social Science (SPSS version 19.0 was used to analyze the data. Descriptive statistics was used to determine the frequency and numerical abundance of each avian species. Shannon Weiner Diversity index was emp loyed to determine the species diversity and evenness in the study area and for each of the two habitats. We calculated the level of similarity in species composition between the two habitats based on the Jaccard/Tanimoto Coefficient; which is one of the metrics deployed to compare the similarity and diversity of sample sets. It uses the ratio of the intersecting set to the union set as the measure of similarity or d issimilarity. Thus it equals to zero if there are no intersecting elements and equals to one if all elements intersect (common species to both sets). This was exp lored using the equation below;

Equation 1
where; -number of element in set A -number of elements in set B -number of elements in intersecting set Shannon Wiener Diversity Index was used to estimate avian diversity of the study area. Effective nu mber of species (Jost, 2006) was used to determine the pattern of distribution (even or uneven) of avian species. The closer the value of Effective number of species to the species richness (actual species count), the more even the distribution of the species and viceversa. Shannon Wiener Diversity Index was calculated using the formular below: Where H' = Shannon Wiener Index Pi = the proportion of individuals of species "i" in relation to the total population of all species.
Loge = Natural logarith m of base e. To get the effective number of species, (the true value of d iversity), we used the equation III. RESULTS A total of 1035 individuals of 69 av ian species fro m 53 genera and 32families were recorded at the end o f a four day transect survey with two days dedicated to each of the habitat types ( Table 2). The most diverse avian family was the Estrildidae family with nine (9) avian species, followed by Colu mb idae with six (6), while Falconidae, Nectriniidae, and Turdidae families had a record of four (4) species each. Five families (Ardeidae, Malaconotidae, Ploceidae, Silv iidae, Sturnidae) and five families (Accipitridae, Bucerotidae, Capitonidae, Viduadae and Psittacidae) followed with three (3) and (2) species respectively. Ho wever, 17 families were each represented by a single species (Table 1). Laughing Dove Streptopelia senegalensis was the most abundant bird species with a total of 96 individuals sited in both habitats. Cattle egret Bulbus ibis and Vinaceous dove Streptopelia vinacea follo wed with 46 and 41 individuals respectively. Jaccard/ Tanimoto coefficient of similarity revealed that the two habitats differed in species composition with a percentage difference of 33.3 %. Jaccard/Tanimoto coefficient was 0.6666 imp lying that the two habitats were 66.7 % similar in avian species composition. A total of 65 of the 69 species were recorded in the degraded savannah habitat (DS), while 50 species were recorded in the Human inhabited habitat (HI). Interestingly 19 and 4 species were unique to degraded savannah and Human occupied habitats respectively. However, 46 species were co mmon to both habitats.
Shannon Weiner Diversity Index for Hu man occupied habitat was 1.56 with an effective nu mber of diversity (true diversity) of 4.77. This was almost the same for degraded savannah with 1.67 and 5.32 for SWI and effective number of species respectively. Investigations to determine the most common feeding guild in the study area revealed that 21 species were frugivorous, while 18 and 16 species were insectivorous and granivorous respectively (Fig. 2).

IV.
DISCUSSION Many institutions of higher learning are adorned with ornamental as well as exotic and native t ree species . Apart fro m the primary ro le of aesthetics, trees are bio logically crucial in climate moderation, carbon sequestration, and mitigation of run-offs and floods during the rains. In addition plants help in air purification, shade provision/ wind break and reduction in noise pollution (Novak and Dwyer 2007).It is also a fact that plants inadvertently provide primary habitats for a vast number of life forms thereby promoting biodiversity. Birds are ubiquitous and have learnt to utilize various habitats both natural and human modified (Borow and Demey, 2004), and as such,we tested whether species assemblage will d iffer between two distinct habitat types; a human occupiedand a degraded savannah habitat. Our thinking was predicated on the notion that habitat structure is a major pred ictor of habitat choice by birds as has been suggested by some studies (Nsor, 2006 . Ho wever, the scale of enquiry (survey duration) may be a limiting factor and a major bias if we were to run a co mparat ive analysis of species richness among the various study sites. Nonetheless, our results indicate,a relat ively higher species richness compared to previous studies given that the survey was conducted for just four days.
Our quest to determine how well avian species make the best of a human modified and degraded savannah habitats was quite revealing; our results suggest that most of the birds in fact 66.7 % use both habitats freely although their distribution may favor one habitat over the other in terms of abundance. For examp le, the most abundant bird species Laughing Dove Streptopelia senegalensis, Cattle egret Bulbus ibis and Vinaceous dove Streptopelia vinacea were more abundant in the Human inhabited habitat than in the degraded savannah, alluding to the fact that perhaps becoming use to human presence was an adaptive advantage. However, it is interesting to note the possible interplay of resource distribution, co mpetition, and habitat patchiness in driving certain individuals of some species to forage in specific habitats even at the risk of predation. This is in keeping with the source-sink theory and the metapopulation concept (Hanski, 1994, Hanski et al., 1995. Birds are known to occupy certain feeding guilds, with several species sharing the same food resources. While most studies on resource distribution focused on the spatiotemporal distribution, few have dwelled on the vertical distribution of avian food resources. However in a recent study, Bakam et al (2018) demonstrated how birds utilize resources along a vert ical gradient. They authors asserted that the more structurally diverse a habitat is, the more likely it is to support diversity, wh ich is in consonance with the works of . In this study, we recorded 21 frugivorous species occupying various heights in a vertically stratified niche arrangement wh ich keeps them often above their zero elevation foraging counterparts -16 species of granivores, while 18 species of insectivores oscillated between different strata, often spending most of their time on the ground hunting for insects. Omnivorous species on the other hand occupied and fed along a vertical gradient while the birds of prey -6 species of carnivores (raptors) swoop down on their prey fro m the top stratum where they often perch for hours . This observed partition of resources reduces interspecies competition wh ile facilitating species cooperation. Against this backdrop, it would not be out of place to say that based on the results of this study, that the relatively h igh level of diversity could be a direct benefit of habitat heterogeneity as reflected in the various feeding guilds highlighted above while also consolidating the notion that vertical stratification of resources is positively associated with avian species diversity and optimizes species richness in concert with other habitat and environmental parameters such as foliage volume and percentage vegetation cover (Karr and Roth, 1971;James and Warner, 1982). Furthermore, the d ifferences in species composition between the two habitats investigated in this study confirm the notion that a heterogeneous habitat supports more species diversity than a homogeneous one (Abalaka and Manu, 2007;Dami et al., 2014). The hu man inhabited habitat was found to be dominated by exotic and introduced plant species planted in a ho mogenous pattern (Pringle et al, 2010). This fact coupled with vehicular and human pres ence may be one of the reasons why more species were recorded in the degraded savannah habitat than the human inhabited one (Imong, 2007). Moreover, most bird species are naturally elusive and avoid habitats that do not offer adequate cover; some of these species e.g. Bush Petronia Petronia dentata, Senegal Parrot Poicephalus senegalus, Tawny flanked Prinia Prinia subflava, Grey Backed Camaroptera Camaroptera brachyuran, Double spur Francolin Poicephaluss enegalus etc.,were found to occur only in the degraded savannah where some remnant shrubby patches offer cover. However because birds are highly mobile apart fro m the flightless ones, they often go beyond their comfort zones to human inhabited areas especially when the habitats offer some movement "corridors" or safe patches to facilitate movement between distinct habitats (Noss, 1991). Th is was the case with some species that are seldom seen in isolated human do minated landscape. Some of these human evading and habitat sensitive species (e.g. Yellow crown Gonolek Laniarus barbarous, Black crown Tchagra Tchagra senegalus and the Red-billed Hornbill Lagonosticta senegala were seen freely foraging in the hu man inhabited habitat in this study. The aforementioned species could easily forage in both habitats because there was really no clear demarcation between the two habitats. Moreover, some portions of the human inhabited habitats tapered nicely into the degraded savannah contiguously (Noss, 1991). This observation emphasizes the need for landscape experts and environmentalist to design campuses and other public facilit ies such that natural patches of indigenous flora will be interspersed with build ings and introduced flora. This will go a long way to encourage diurnal movements of avian species between patches and on a broader scale more biodiversity.

V. CONCLUSION
The study identified certain anthropogenic activities that may be detrimental to avian species wellbeing and abundance in the study area if urgent actions are not taken. These include but not limited to; indiscriminate and unregulated extraction of fuel wood, excessive conversion of remnant woodland to agricultural fields, unsustainable extraction of plants of ethno-botanical importance, unregulated movement of pedestrian and poachers into the college through multiple entry and exit routes. We urge the college management to as a matter of urgencyblock all unauthorized entry and exit routes to check unsustainable harvest of fuel wood. More native tree species should be reintroduced to mute the invasive effect of exotic species and restore networks of interactions that have been broken with the exit of native key stone tree species. The campus has potential to be a major refuge for birds and other smaller invertebrate species if all stakeholders rejig their co mmit ment to nature and their stewardship obligation to biodiversity.