Diversity and abundance of bird species

The goal of this study was to identify the diversity and number of bird species on campus. The research was conducted in September 2017 by splitting the school environment into two habitats: human settlements and bushland. The abundance and diversity of birds in these two areas were compared. The point count approach was used to collect data. The Shannon-Wiener diversity index (H') was used to calculate species diversity. A total of 230 birds and 19 bird species were counted. The study discovered a considerable disparity in both bird abundance and diversity across environments.The findings of the study showed that human settlements can serve as home for birds. Thus, conversation of habitats should be encouraged to make human settlements and bushlands to be considered as useful homes for birds.

Factors Affecting Bird Diversity

Introduction

Although many parts of the world were once extensively forested, the forest cover has reduced significantly as from the past few years. Prior to large scale deforestation, areas were covered in natural forests but today natural as well as semi-natural forests have become rare. Despite this, forest remains the most important home for birds since it supports the largest percentage of bird species whereas a small fraction of bird species live in human habitats. Humans are responsible for loss of natural habitats of birds through their engagement in different activities like farming, burning of charcoal, settlement, in addition to pole cutting and collection of wood as firewood. Such deforestation practices have significantly destroyed the natural home for birds, influencing their variety as well as variability. Birds are very selective when it comes to their habitat; however, the utilization of land has made them to experience change of habitats. Bird diversity studies by Herrando and Brotons (2002); Graham et al. (2014); Imai, Nakashizuka and Oguro (2017); were confined to the detrimental effects of destruction of forests to meet human demands. Despite that, it is apparent that human activities vary with places and as a result the effect of such activities on birds also varies. Some birds however respond positively to changes in their habitat whereas others consider change of their habit as a main threat.

Birds are noticeable are they play a critical role in the ecosystem since they occupies different trophic levels, including consumers and predators. The occurrence of birds is also linked not only to environmental health indicator, but also plant pollinators, dispersal of seeds in addition to control of pests (Ramchandra 2013). Moreover, they are refreshment living things due to their distinctive colors and songs, and showy displays. Based on these facts, it is apparent that the study on the factors that affect bird diversity in respect their habitats is important because it will elaborate on bird species diversity, their distribution as well as abundance in natural as well as urban habitat.

It is argued that many years before the introduction of the university campus in this place, the area was occupied by natural forests. With such forests, it is possible that the bird species were very many. The abundance of birds was also significant since they had natural habitat. However, anthropogenic activities took place in this region due to rise of human population. The forests were destroyed to allow urban settlement as well as to allow open land for different activities. The effect of these human activities is evidenced by the biodiversity and abundance of birds as a result of isolation in addition to fragmentation. Sharp trop in abundance as well as loss of many bird species because of human interference has been discussed in different studies. For instance, studies by Ramchandra (2013); Graham et al. (2014); Imai, Nakashizuka and Oguro (2017); show that deforestation for development of settlemts including urban centers cause habitat loss in the globe. Some bird species like the Tanzanian Mountain Weaver (Ploceus nicolli) together with other bird species referred to as Banded Green Sunbird (Anthreptes rubritorque) has been included in the endangered and threatened species because of human activities (Ramchandra 2013). Ramchandra’s study also failed to find these species of birds in the reserve where they were spotted earlier. The findings shows that there is high likelihood these bird species were displaced from the area because of variation of land use. Since birds are very important for identification of environmental changes, the information on the bird species in the university campus will be important.

The aim of this study is to determine as well as compare the diversity, abundance in addition to distribution of avifauna in varied habitat types within and areas near the university campus. It will also present recent information to the existing birdlife surveys as well as add to the recently collected data and set up a basis for long-term research on birdlife in the campus. The study will also raise awareness on the factors that influence the diversity and abundance of bird species in a given area. In addressing this, the study will determine and compare the diversity, distribution, plus abundance of different species of birds. It will also link bird abundance with different habitat features. The study will also involve preparation of checklist of different birds within the area of study.

The research hypothesis for the study states that: Bird species richness is affected by habitat degradation.

Specific testable hypotheses states that: Bird species richness is affected by habitat degradation.

Bird species richness will be greater in the bush-land than in urban habitat. Urban habitat in this study is associated with construction of buildings and land clearing.

The null hypothesis for the study states that: Bird species richness is not affected by habitat degradation.

Materials and Methods

Description of the Study Area

The study was carried out in the university campus particularly in two areas, urban and bushland in accordance to the bird survey techniques (Gregory, Gibbons, & Donald 2004). Urban areas were characterized with buildings and few trees. The bushland on the other hand consisted of dense and mid dense vegetation cover with trees approximately 10 to 30 meters in height.

Study Design

The study was carried out in the campus starting from the urban areas to the bushland. Data were collected during dry season September 2017. The area of study were stratified into settlements and natural habitat (urban and bushland). Areas within the bushland were defined as areas with high density of trees and the urban settlements as areas with low density of trees. The location of each habitat was geographically referenced with the aid of handheld GPS.

Random sampling method was employed to select 3 counting points of 50 meters apart. The point count method is preferred for uneven terrain as well as dense undergrowth since detection of birds by other techniques is often difficult (Gregory, Gibbons, & Donald 2004). Types an percentage of vegetation cover as well as type and level of human disturbance together with noise miner abundance was measured in every point of count.

Data Collection

Birds were counted within sampling points in every habitat. Upon selection and reaching a point of count, approximately 3 minutes were granted to allow the birds to settle following the disturbance we might have caused (Bryan et al. 1984). Five minutes were utilized to count plus record all birds spotted within 50 m radius. The study was carried out in the morning as from 9 am since this is the period associated with the activeness of birds. Date, habitat type, actual weather conditions, bird species, and number of birds were recorded. The study however involved diurnal birds since there was no special equipment for detecting nocturnal birds. The quality of the collected data was enhanced throughout the period of study by regularly testing the species of birds observed, the estimated distance, and the number of birds observed.

Data Analysis

The variation in abundance of birds between different habitats was tested using One-Way ANOVA (Kruskal Wallis test) in which habitats acted as independent variables and the abundance of birds as a dependent variable. Species diversity was evaluated using the Shannon-Weiner diversity Index. Shannon-Weiner diversity index (H’) was preferred to other methods because it accounts for richness and evenness of bird species (Morris et al. 2014). Morris et al. chose this method because “it represents the uncertainty about the identity of an unknown individual” (Morris et al. 2014, pp.3415). According to (Shaheen et al. 2011; Morris et al. 2014), in evenly distributed system one can find an individual that belongs to any species, causing uncertainty in foretelling its identity. The method assumes all species are represented in a study, hence, giving species diversity in diverse habitat. With this method, we could find not only the abundance of species, but also the distribution of those species in the habitats used for the study (Sarma & Das 2015). I used this method to determine the diversity of bird species in the two habitats.

Shannon Diversity Index

s

H = ∑ - (Pi * ln Pi)

i=1

Where:

H is the Shannon diversity index, Pi the fraction of the whole population comprising species i, S the number of encountered species, and ∑ the sum of species from 1 to s.

Bird species’ checklist was created in Microsoft Office Excel to show species and their respective habitats.

Results

Abundance

Results show significant difference in abundance of specific species of birds between habitat types (Magpie-lark 9, 2; Willie Wagt 1, 15 in urban and woodland areas respectively). Density of specific species of birds was highest in urban areas when compared in the woodland (Table 1).

Table 1: Abundance of birds within two habitats in September 2017

Habitat

Number of birds

Mean abundance

Human developed habitat

151

0.481

Woodland

79

0.419

The number of bird species observed in urban settlements bypassed those observed in the woodland. In the urban settlements there were 15 different species of birds whereas in the woodland there were 9 species of birds. The abundance of birds was also highest in urban settlements when compared with the woodland habitat (Table 1 and Figure 1).

Species Richness

Figure 2: The Richness of Bird Species in Human Settlements

The number of individual birds observed in areas disturbed by human activities reduced in number in almost a consistent manner. The species richness “S” increased as the number of birds observed increased at first, and then reduced slowly.

Figure 3: The Richness of Bird Species in Bushland

Just like in the human settlements, the richness of species increased as the number of observed birds increased, and later reduced significantly.

Diversity

Biodiversity Index Graphs

The recorded figures of the observed species of birds show high species dominance in urban settlements and low dominance in woodland. Equally, Shannon-Weinner diversity index was more in habitats with human disturbance compared to habitats with less human activities, the woodland.

Discussion

Bird Abundance and Diversity

Abundance

There was significant difference in bird abundance between the two habitat types. The great difference in abundance of birds, with high abundance being recorded in urban settlement, can be as a result of poor observation of birds in the woodland because of tall trees. The result showed higher bird abundance as well as densities in areas associated with extensive human activities and decreased substantially towards woodland or forest areas. The findings of this study were contrary to Lowe, Taylor, and Major’s (2011) findings. In their study, they noted that the richness of bird species decreased as they moved from the bushland to the residential or commercial areas. However, some of their findings concurred with this study. For instance, they noted that the native species richness dropped significantly with urbanization. Similarly, they learned that exotic species richness was extremely high in commercial sites. In other words, the abundance of native species dropped as the abundance of exotic species increased as they moved from the bushland to the residential areas. The findings of Lowe, Taylor, and Major (2011) also backed the finding of this study by identifying that the abundance of specific species of birds such as Common Mynas was influenced by the types of the habitat. The abundance of these birds dropped as one moved from commercial, residential, and to the bushland sites. This study as well as Lowe, Taylor, and Major (2011); Haythorpe, Burke, and Sulikowski (2013); Lowry, Hill, and Wong (2010); and Audet, Ducatez, and Lefebvre (2015) conclude that areas disturbed by human activities offers heterogeneous habitats that are suitable for birds that are tolerant to auditory disturbance. Other studies on birds abundance in human settlements (Cleary et al. 2016; Galbraith et al. 2015; Parsons, Major, and French 2006) also noted similar result and came to a conclusion that the increased abundance of birds in settlements were influenced by habitat heterogeneity like trees, man-made gardens, and buildings.

It was observed specific species of birds were more abundant in the woodland when compared in the settlements. This could be as a result of greater openness in such habitat which initiates the survival of shrubs that serve as food and shelter for the bird species (Shochat et al. 2010). However, the forest habitat recorded small number of birds. The lowest number of birds in this habitat can be attributed to forest degradation as a result of cutting down trees for fuel and clearance of trees for other human activities (Imai, Nakashizuka, and Oguro 2017). The reduction in cover for escape from predators and shelter, and decline of food supply as well as breeding sites could have influenced the rise of competition between species hence lowering their number as reflected in the result.

Diversity

Bird species diversity was higher in high human activity areas than in the forest. The higher species diversity noted in areas inhabited by man could be as a result of the increased number of exotic birds. Exotic birds have adapted to the environments occupied by man. Equally, it could be as a result of habitat heterogeneity. Human settlement areas have trees and buildings that provide birds with homes. The lower number of bird diversity in the forest might be as a result of low forest cover due to extensive clearance of trees to accommodate human activities. The findings of this study are in tandem with many other studies (Graham et al. 2014; Imai, Nakashizuka, Uguro 2017; Cleary et al. 2016) that private lands provide habitat in addition to resources to many birds residing in human-dominated areas. High species diversity as well as higher dominance evidences complex community characterized with great species interaction. However, many studies (White et al. 2005; Montague-Drake et al. 2011) show that the diversity of birds is great in forests when compared with settlement areas. The observance of low bird diversity in the forest might have been as a result of few exotic bird species following the clearance of natural habitats. The low diversity might also been as a result of the sampling points. For instance, the third sampling point in the bushland was very dense and had very few numbers of birds. Perhaps the observance of few birds was due to the dense and tall vegetation cover that made it hard for observers to spot birds or for the birds to fly.

Distribution

The selected habitat types recorded only 19 bird species. This necessitates conservation of environment and birds. According to Ramchandra (2013), the distribution of bird species in any setting often follows the formation of the environment in addition to their habitat requirement. The argument corresponds with the findings of this study in which habitat specificity in addition to generalization was spotted. For instance, Raven (Corvus corax), Magpie (Pica pica), Magpie-lark (Grallina cyanoleuca), Willie Wagtail (Rhipidura leucophrys), and Noisy Miner (Manorina melanocephala) were observed in the two habitats. Contrary to this, Red-rumped (Psephotus haematonotus), Rock Dove (Columba livia), Crested Pigeon (Ocyphaps lophotes), Rainbow Lorikeet (Trichoglossus moluccanus), Sulphur-crested (Cacatua galerita), Galah (Eolophus roseicapilla), Masked Lapwing (Vanellus miles), Common Blackbird (Turdus merula), Welcome Swallow (Hirundo neoxena), Common Myna (Acridotheres tristis) were recorded in human developed habitat. Although human settlements are characterized with diverse built habitats besides green patches, many bird species have adapted these complex habitats (Ramchandra 2013). The assertion is explained by the presence of ecological expectations for the bird species provided by a mix of a setting with buildings plus garden patches. The study also noted four different species of birds in the bushland some of which were also observed in other studies. The list includes House Sparrow (Passer domesticus) that were observed in (Cleary et al. 2016; Galbraith et al. 2015; Audet, Ducatez, Lefebvre 2016) studies. Other bird species spotted in the forest include Pied Currawong (Strepera graculina) which was also observed by Haythorpe, Burke, and Sulikowski (2013) study. White-browned scrubwren (Sericornis frontalis) and Grey Shrike-thrush (Colluricincla harmonica) were also observed in this study.

Conclusion and Recommendations

The diversity of bird species was higher in areas with higher human activities. The higher diversity suggests great number of exotic species of birds as well as adaptation of birds to the environment capitalized with human activities.

The study also shows that human activities influence high diversity since buildings and farmland are crucial part of the birds’ ecosystem. They harbor great number of birds when compared with the woodland.

The variation of available resources in different habitats like sites for breeding, forest cover, and food restrict some bird species to specific types of habitat while permitting other birds species to be extensively distributed.

It was concluded from the study that any activities by man that alter with the structure of birds’ habitat affect the abundance, diversity as well as the distribution of birds.

Recommendations

The bird diversity in the university campus needs to be improved in both habitats. This will be achieved by encouraging tree planting in human occupied environment as well as the bushland. Doing this will boost bird species diversity and as a result make human settlement and the forest not to be considered as lost habitats for birds, but rather viewed as habitats that are properly managed to support the diversity of bird communities.

Since the university community presents itself as a community with inadequate awareness on the importance of birds in the ecosystem as indicators of a healthy environment and control of pests, many studies need to be conducted on the diversity and abundance of birds within the university. The department of Natural Resources should also create awareness in occupiers of the school setting so that the role played by birds in the ecosystem can be recognized.

It is evident that research findings on biodiversity of birds are not passed to the society. Due to this, members of the societies do not know the importance of research studies on birds. Researchers should work with the department of Natural Resources to ensure members of the society have been informed about the importance of such study.

This study involved only two habitats, settlement and bushland, as the areas for collecting samples. Such limitation of areas of study affects the quality of the research. Individuals who will carry a similar research study should consider expounding their areas of study to have adequate information on the status of bird species biodiversity and abundance.

The results of this study were greatly influenced by the inability to observe birds in some sampling points. Equally, the observation of birds took only two weeks. The environmental factors associated with different times of the year might have influenced the availability of birds in the areas of studies. Thus, the conclusion made from what was observed is biased. Biasness in a similar study can be reduced by expounding the duration of a research study to approximately 2 months. For instance, the study by (Montague-Drake et al. 2011) involved 46 farms. “The sites constituted a range of structural conditions-old growth, natural seedling regrowth and coppice regrowth woodland” (Montague-Drake et al. 2011, pp.1385). The surveys for this study were conducted for more than 1 year. Similarly, a study by White et al. (2004) took place in an urban area that was divided into broad habitat types; parks, native streetscapes, exotic streetscapes, and recently developed streetscapes. The surveys for this study took place between March and June, a period of about four months. Broad habitats in addition to sufficient time facilitates collection of qualitative and quantitative data that is necessary for making a viable conclusion.

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