Role Of Habitat On Avifauna Community Composition Biology Essay

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In order to determine why a community consists of certain species, studies measuring habitat structure and floristics are conducted as well as the survey of avifauna species present within those habitats (Macnally 1990; Johnson 2007). Both floristics and habitat structure play an important part in determining the community composition of avifauna within habitats (Kikkawa 1968; Rotenberry 1985; Tews, Brose et al. 2004; Johnson 2007). There is strong evidence to suggest that floristics is the dominant factor at a local scale (Rotenberry 1985). The results of this study are in support of the view that riparian zones in particular seem to stand out from other habitats in terms of abundance, richness, diversity and composition in general (Woinarski, Brock et al. 2000; Schneider and Griesser 2009).

INTRODUCTION

It is well documented that different avian species are associated with particular habitats (Kikkawa 1968). Of much debate and the subject of many studies is what actually determines avifauna community composition; is it habitat structure or floristics that influences these distributions? (Macnally 1990). In an attempt to explain why some communities have a particular preference for certain habitats, avifauna studies conducted have measured features of habitats like vegetation composition and its structural diversity (Johnson 2007). Most habitats offer a range of structural niches that allow species the opportunity to centre activities in different parts of vegetation (Cody 1985). Therefore, in measuring the features of habitats, it is possible to evaluate patterns of abundance, species richness, the diversity and evenness within a community (Johnson 2007). Abundance is defined as the total of all birds recorded within a community while species richness is the number of species within the community (Smith 2001). Species diversity relates to species richness in the community and the relative abundance of those species and finally evenness measures how individuals of each species are numerically distributed within the community (Smith 2001).

The aim of this avifauna community survey is to measure abundance, richness, diversity and evenness of 9 different habitats, and determine any likely association between these findings and their habitats.

HO - Riparian zones support a distinct community composition and are greater in abundance, richness and diversity than other habitat types

Ha - Riparian zones do not support a distinct community composition and are not greater in abundance, richness and diversity than other habitat types

METHODS

Avifauna surveys were carried out at 9 different locations in order to represent a suite of different habitat types and their community compositions (refer to Figure 1). The 3 main locations for each of the 9 sites include the Palmetum, Ross River and the JCU campus. Brief descriptions about the habitat for each of the 9 sites are listed in Table 1.

1

2

3

5

4

6

7

9

8

Figure 1. Site Map of all 9 sites for avifauna surveys

Table 1 - Site Descriptions for all 9 sites

SITE

DESCRIPTION

Site 1

Closed canopy Rainforest at the Palmetum

Site 2

Savannah around pond at the Palmetum

Site 3

Riparian vegetation along Ross River

Site 4

Dry rainforest on the JCU campus

Site 5

Open mown eucalypt woodland on JCU campus

Site 6

Creek-line paperbark woodland on JCU campus

Site 7

Eucalypt woodland with understorey shrubs on JCU campus

Site 8

Open ironbark woodland with grassy understorey on JCU campus

Site 9

Creek-line Leucaena thicket, opposite Technical College

Surveys for sites 1, 2 and 3 were conducted on Tuesday morning; sites 4, 5 and 6 on Wednesday morning and sites 7, 8 and 9 on Thursday morning. Each group on their respective day collected data for thirty minutes between 6.45am and 7.15am. At each site, the group made their way along a marked transect and record all species sighted. At this time, habitat information such as flowering and fruiting trees, canopy cover, shrub and herb layer, water availability, topography and anthropogenic disturbances were recorded.

The site 6 group collected data at the creek-line paperbark woodland on JCU campus (refer to Figure 2). The group recorded all birds sighted within the dry creek bed and in the surrounding vegetation near the creek bed. A full site description is listed in Table 2.

Table 2. Description of Site 6 (creek-line paperbark woodland)

FEATURE

DESCRIPTION

Vegetation

Melaleuca leucadendra, also Lophostemon (Swamp Box), Lysiphyllum (Native bauhinia), Pongamia pinnata (Indian Beech), Acacias dominant, Zizyphus (Chinee apple), Corymbia tesselaris (Moreton Bay Ash) on upper bank with grassy understorey

Canopy cover

20-30%

Shrub cover

10%

Herb cover

20%

Flowers

Present (Pongamia)

Seeds

Present

Topography

Creek bed, stoney substrate, steep sloping banks

Irrigation

Water available in small pools

Disturbances

Animal noises from vet science compound

Melaleuca woodland 2010.JPG

Melaleuca woodland2 2010.JPG

Figure 2. Site 6 - riparian paperbark woodland on JCU campus (Photos taken by Carrie Preite)

The data for all groups was collated into a spreadsheet and analyzed. Total abundance, species richness, evenness and diversity were calculated for each site using the computer program Excel. Total abundance is calculated by summing all birds within a site and richness by summing the number of different species. Diversity, a measure of species richness and abundance was calculated using the Simpsons Diversity Index D = 1/ ∑ Pi2. This is a dominance index and by squaring Pi, rare species within the community have little effect on the results. Species evenness measures how numerically equal a community is distributed and is calculated by E = D/S. When E = 1 the community is evenly distributed, when E = 0 it is unevenly distributed. A hierarchical cluster analysis was performed using Wards method in the statistical program SPSS. This is a classification analysis and it measures the sites based on similarity or dissimilarity. Similar communities are clustered together and dissimilar communities are spread apart on the dendogram.

RESULTS

The total abundance of each site is displayed in Figure 3. Sites 3 and 5 were most abundant recording a total of 95 and 93 birds. Sites 2 and 7 follow in order of abundance recording 68 and 55 birds and sites 6 and 9 record 45 and 37 birds. At the lower end of abundance are sites 1 and 4 recording 27 and 23 birds. Site 8 was lowest in total abundance recording 13 birds, a difference of 82 birds between sites 3 and 8. The abundance over all sites is quite varied.

Figure 3. Histogram of total abundance for all bird species across all nine sites

Species richness displayed in Figure 4, records site 3 as highest richness with 21 species. Site 6 records 16 species and is followed by sites 5, 7 and 9, all recording the same richness of 15 species. Sites 1, 4 and 2 follow on, with site 1 recording 12 species, site 4 with 11 and site 2 with 10 species. Site 8, lowest in richness records just 8 species, a difference of 13 species between highest and lowest abundance. A gradual decrease in richness can be seen through all the sites.

Figure 4. Histogram of species richness for all bird species across all nine sites

Diversity, displayed in Figure 5 records site 9 having the highest diversity with an index of 8.8, followed by site 3 with an index of 8.4. In the middle range of the index is site 6 with 7.4, site 7 with 7.2 and site 1 with 7.1. At the lower end of the index is site 5 with 5.6 and site 2 with 5.0. The sites of lowest diversity are site 8 with 4.8 and site 4 with 4.4 on the index.

Figure 5. Histogram of diversity for all bird species across all nine sites

Species evenness is displayed in Figure 6. Site 8 was highest in evenness recording 0.604, followed by site 1 with 0.590 and site 9 with 0.589. Following on is site 2 recording 0.500, site 7 with 0.479 and site 6 with 0.460; these sites are closely matched in evenness. At the lower end of evenness are sites 3 with 0.401 and site 4 with 0.397 and lastly site 5 recording 0.376.

Figure 6. Histogram of evenness distribution of species in community composition across all 9 sites

The cluster analysis of the 9 sites is summarized in a dendogram shown in Figure 7. The first cluster of sites 1, 4, 6, 7, 8, and 9 are most similar to each other in composition but dissimilar to cluster 3 which consists of sites 2 and 3. Cluster 2 consists solely of site 5 and has similarities to cluster 1 and cluster 3 but is dissimilar enough to be placed in a cluster alone.

Rescaled Distance Cluster Combine

C A S E 0 5 10 15 20 25

Label Num +---------+---------+---------+---------+---------+

Site 4 4 -+

Site 8 8 -+-+

Site 9 9 -+ +---+

Site 1 1 ---+ +-----------------------------+

Site 6 6 ---+---+ +-----------+

Site 7 7 ---+ | |

Site 5 5 -------------------------------------+ |

Site 2 2 ---------------+---------------------------------+

Site 3 3 ---------------+

Figure 7. Dendogram of Hierarchical Cluster Analysis for all 9 sites using the Ward Method

Figure 8 displays the total abundance for each of the clustered sites. Cluster 2 has the highest abundance with 93 birds, followed by cluster 3 with 81 birds and lastly, cluster 1 with total of 33 birds.

Figure 8. Histogram of total abundance for the clusters 1,2 and 3

Figure 9 displays species richness for each of the clusters. Cluster 3 records the highest species richness of approximately 16 species followed by cluster 2 with 15 and finally cluster 1 with approximately 13 species.

Figure 9. Histogram of species richness for clusters 1, 2 and 3

Figure 10 displays the diversity index for each of the clustered sites. Cluster 3 has the highest diversity index of 6.7 followed by cluster 1 with an index of 6.6 and finally is cluster 2 with an index of 5.6.

Figure 10. Histogram of diversity for the clusters 1, 2 and 3

Figure 11 displays the distribution of evenness between the clustered sites. Cluster 1 records the highest evenness of 0.51 followed by cluster 3 with 0.45 and finally cluster 2 with 0.37.

Figure 11. Histogram of evenness for clusters 1, 2 and 3

DISCUSSION

The results show site 3 (riparian zone at Ross River) as being the highest in total abundance and richness of all the sites surveyed. Previous studies of riparian zones show evidence in support of higher abundance and richness within these habitats (Woinarski, Brock et al. 2000; Schneider and Griesser 2009). It is suggested this is due to higher resource availability, and in northern Australia, is attributed to vegetation cover consisting of Melaleuca spp, Eucalyptus spp and rain forest plants (Woinarski, Brock et al. 2000; Schneider and Griesser 2009). Habitat structure, in particular, one that is structurally complex, has often been connected to high species abundance, richness and diversity (Kikkawa 1968; Tews, Brose et al. 2004; Johnson 2007). The reasoning is, the more complex the habitat structure, the greater potential for resource segregation (Kikkawa 1968; Tews, Brose et al. 2004; Johnson 2007). Site 9 (creek-line Leucaena thicket), and again site 3 record the highest diversity index for all sites. Both of these sites are more structurally complex than other sites with canopy and shrub cover plus a herb layer, allowing for greater resource segregation and therefore higher diversity. It is noted that site 9 has low abundance in comparison to the other sites, but has relatively high species richness which accounts for the high diversity index. Site 8, the open ironbark woodland with grassy understorey at JCU recorded the most even distribution of species within the community. Evenness is sensitive to sample size and therefore it is suggested that site 8, having the smallest sample size may account for the high evenness of species.

The dendogram groups sites 1, 4, 6, 7, 8 and 9 together in cluster 1 as being most similar to each other. There are a number of honeyeater species found within cluster 1. The blue-faced honeyeater (sites 1, 6 & 9), noisy friar (site 4), helmeted friar (sites 1, 4 & 7) plus a number of other honeyeater species (sites 1, 4 & 7). Eucalyptus spp., Melaleuca spp. and Acacia spp. are common to the sites in cluster 1 and it is noted that honeyeaters prefer these species of vegetation (Frith 1976). Blue-faced honeyeaters favour Eucalyptus spp. and Melaleuca spp. and can be found around the edges of rainforests (Frith 1976). Noisy friar prefers sclerophyll forests (wet/dry) or open woodlands and the helmeted friar can be found in paperbark swamps or monsoon forests (Frith 1976). The noisy friar and helmeted friar may be found in association with each other (Frith 1976). Another common feature in cluster 1 is the presence of water either in small pools or located nearby. In the dry season blue-faced honeyeaters stay close to water sources (Frith 1976). It is suggested that the numbers of honeyeaters found within cluster 1 are related to the floristics within cluster 1 as well as water availability. Previous studies have found an association between vegetation species composition and avifauna composition (Rotenberry 1985). Furthermore, this association is significant at a local population level (Rotenberry 1985).

Cluster 2 consists of site 5 (Eucalypt woodland at JCU). There are high numbers of rainbow lorikeets found within cluster 2. Rainbow lorikeets are found in many different habitats including, schlerophyll forests (wet/dry), tropical rainforests and tall open Eucalyptus woodlands (Frith 1976). Rainbow lorikeets prefer Eucalyptus spp. but will exploit flowering Callistemon spp. and Grevillea spp. for nectar (Frith 1976). Unless understorey species are flowering, physical structure of a habitat appears insignificant and communities even inhabit woodlands with an understorey layer entirely of grass (Frith 1976). Vegetation composition of cluster 2 is dominated by Eucalyptus platyphylla. Flowers of Callistemon spp. are present plus an extensive herb layer. Again, it appears that vegetation composition is the dominant factor for species composition within this site (Rotenberry 1985).

Cluster 3 consists of site 2, (savannah around pond at Palmetum) and 3, (riparian zone at Ross River) grouped together in terms of similarity to each other. The common factor for both sites is the riparian zone. High numbers of welcome swallows and magpie geese are recorded in cluster 3. Welcome swallows feed predominately on insects, which are frequently found around riparian zones and therefore, welcome swallows are commonly found around riparian habitats but are also found in savannahs and open woodlands (Frith 1976). Magpie geese (waterbird species) are commonly found in wet grasslands and in floodplains (Frith 1976). As previously stated, there is strong evidence for distinct communities inhabiting riparian zones (Schneider and Griesser 2009).

There is plenty of evidence in support of habitat structure and floristics affecting the composition of avifaunal communities (Macnally 1990). It appears within this survey, at a local scale, floristics is the dominant factor for avifaunal community composition (Rotenberry 1985). Riparian zones in particular, with complex habitat structure and the presence of water, are high in abundance, richness and diversity and have quite distinct communities from those of other habitats (Kikkawa 1968; Tews, Brose et al. 2004; Johnson 2007; Schneider and Griesser 2009).

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