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COMMUNITY ECOLOGY OF TROPICAL BIRDS

E.A. Jayson, C. Sivaperuman
  • Country of Origin:

  • Imprint:

    NIPA

  • eISBN:

    9789389907827

  • Binding:

    EBook

  • Number Of Pages:

    294

  • Language:

    English

Individual Price: 121.43 USD 109.29 USD

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Community Ecology of Tropical Birds, the tropical ecosystems is one of the most biological diverse habitats on the earth. Seventy six per cent of all centers of avian endemism occur in tropical regions and the same is true for many plant and animal communities. Birds are important component of biological diversity and their ecological, cultural, recreational and economic benefits are recognized universally. They act as vital links in many food webs and often serve as highly visible biological indicators of ecosystem health. Many bird populations are declining all over the world due to habitat loss and fragmentation, predation, pesticide use, invasive exotic species and other factors. This book is about the ecology of tropical bird community, all together 12 chapters are described and divided into two parts. The first part of this book looks at the forest bird community including status and distribution, species-abundance relationship, seasonal changes, vertical distribution and habitat utilisation. The second part provides detailed ecology of wetland bird community. This book will be an invaluable resource for field scientist, researchers, students, and naturalists in the field of Ornithology.

0 Start Pages

Preface Forest Bird Community The community ecology of birds was carried out in Silent Valley National Park and Mukkali areas in the tropical forest of Southern Western Ghats from May 1988 to April 1993. The study area is situated in Palakkad District, Kerala State (11° 3’ and 11° 13’ N latitude and 76° 25’ and 76° 35’ E longitude). The major forest types in the area are west coast tropical evergreen forests, subtropical broad leaved hills forests, moist deciduous forest and grass lands. The study on birds was based on direct observation and density of birds was estimated using variable-width line transects in each month. To correlate the diversity of birds to the vegetation in the area, vegetation parameters like percentage composition of trees, vegetation profile diagram and foliage height profile of Silent Valley and Mukkali were prepared. In addition to this, girth class distribution of trees, maturity index of vegetation and diversity of trees were also measured using standard methods. Total of 137 taxa of birds were recorded from the two areas. A variation in species composition was observed during the different months and a significant increase in the number of species and total number of birds was observed during the summer months. The resident birds showed a stable population while the second group of local migrants registered an increase in abundance during dry months. Species richness indices were high at Mukkali and low at Silent Valley. Species-abundance models at these two places followed truncated lognormal distribution. Proportional abundance indices like Shannon Index, Simpson Index, Hill’s numbers showed identical values at both the areas. Shannon Index of the two areas showed significant difference. Similarly indices like Jaccard Index, Sorenson Index and Sorenson quantitative Index showed that the two areas were similar in bird communities only at 40 per cent level. Rainfall is found to have significant negative correlation on the species richness, than on the total number of birds or density at Silent Valley. Similarly, significant difference is obtained between summer and monsoon season in total number and density of birds at Silent Valley. But no such difference is obtained at Mukkali. A significant positive correlation was obtained between the total number of birds in each month and the abundance of flowers. However, no significant correlation was obtained between total number of birds and other food items, such as insects and fruits. Bird species used all the seven foliage height categories identified at the Silent Valley and Mukkali. High species richness of birds was observed at lower and middle levels at both the places. Four diversity indices were worked out for seven foliage height categories at the two sites. The diversity was in a decreasing order from the lowest to the highest stratum. At Mukkali, highest diversity was found in the third stratum (6-10). A significant positive correlation was obtained between foliage abundance and total number of birds and also with species richness in each height stratum, at Silent Valley and Mukkali. In all the height strata, omnivorous and insectivorous birds were of equal abundance followed by others. Foraging ecology observations revealed that birds were using basically 5 foraging methods and gleaning was a principal method used by 13 species followed by probing. No complete General Overlap was found in any of the foraging parameters studied. Insectivorous birds were maximum in both of these areas followed by omnivorous and frugivorous birds. There were more frugivorous birds at Silent Valley than at Mukkali. Microhabitat utilization of birds showed that branches of trees and foliage were highly utilized followed by others. The general overlap in microhabitat use was low in both the study areas. The study analyses, bird community parameters and show its linkage to the habitat, vegetation and climatic parameters. Comparison of the two tropical forest bird communities with different supporting vegetation show the variations and similarities in the parameters studied. The evaluation of the study areas shows the value of this reserve forest, which is comparable to the world standards and recommends its preservation to function as a buffer zone for the Silent Valley National Park. Wetland Bird Community This study has been conducted in the Kole lands of Thrissur, Kerala which is part of Vemband-Kole Ramsar site during November 1998 to October 2001 (10° 20’ and 10° 40’ N latitudes and between 75° 58’ and 76° 11’ E longitudes), with an extent of 13,632 ha spread over Thrissur and Malappuram Districts, Kerala State. The Kole wetlands are low lying tracts located 0.5 to 1 m below MSL and it remains submerged for about six months in a year. Climate of the area is moderate and three different seasons are found in the study area. The temperature varies from 28°C to 31.5°C and the average annual rainfall is 3,200 mm and the maximum rainfall is received during June and July. Community parameters of birds were studied based on direct observation and four intensive study areas were selected for detailed observations. Density of birds was estimated using total count method. The food and feeding patterns of five species were studied. In order to compare the availability of invertebrate fauna with the bird community, their abundance in different microhabitats was estimated during three migratory seasons. For this, mud samples were collected from different microhabitats by Naturalist’s dredge method and invertebrates were estimated. Macro fauna was collected from shallow water, mud flats and paddy fields using 1 m X 1 m quadrat method. Microhabitat utilisation pattern of 11 selected bird species was studied. Conservation awareness of local people was assessed through structured questionnaire survey by directly interviewing the respondents in the study area. Species richness, abundance, diversity indices, density, seasonal fluctuations of bird community, food and feeding of selected bird species, habitat utilisation and conservation problems of wetland birds were recorded and analysed using statistical packages. A total of 182 taxa of birds, belong to 50 Families under 16 Orders were recorded. Of the 182 species, 100 were resident, 81 migrants and one straggler. Among the migrants, 49 species were trans-continental migrants and 32 local. Out of the 182 species, 48 were new records for the area. One vulnerable and five near threatened species were recorded, namely Spot-billed Pelican (Pelecanus philippensis), Darter (Anhinga melanogaster), Painted Stork (Mycteria leucocephala), Oriental White Ibis (Threskiornis melanocephalus), Ferruginous Pochard (Aythya nyroca), and Pallid Harrier (Circus macrourus). Species richness of birds varied in different months and the highest recorded number of species was 97 during December 1999 and the lowest was 15 during June 1999. The species richness increased during the migratory season and decreased during the southwest monsoon. Total number of birds varied from 35 to 8,033 individuals in a month. The highest number of birds (8,033) was recorded during November 2000 and the lowest (35) during June 1999. The highest diversity Index (H’) was recorded in December (3.01) and lowest in October (2.11). The highest density of birds was recorded in December (29,158 birds/ha) followed by November (24,373 birds/ha). Among the four intensive study areas, species richness was highest at Kanjany (121) followed by Parappur (117), Enamavu (94) and Chettupuzha (71). Monthly analysis showed that the highest number of species was recorded at Parappur during December (79) and the lowest at Chettupuzha during June (10). The maximum number of birds was recorded from Kanjany (73,604) during December and the minimum from Chettupuzha (140) during July. The highest diversity Index (H’) was observed in June (2.90) at Parappur and the lowest in February (1.53) at Parappur. The highest density was in December (53,994 birds/ha) at Kanjany and the lowest was in July (103 birds/ha) at Chettupuzha. Out of the 82 wetland bird species observed, Whiskered Tern (23 per cent) was highest in dominance followed by Little Egret (13 per cent) and Little Cormorant (11 per cent). Species richness and abundance were highest in the dry season of 2000 (120) and lowest in the wet-I season of 1999 (46). Diversity Index (H’) was highest in the dry season of 2000 (3.19), followed by the dry season of 2001 (2.89). Species richness was highest in the third year (2000-2001) migratory season (127) followed by second year (1999-2000) migratory season (119). The highest abundance of birds was recorded in the third year migratory season (1,88,006) and lowest in the first year migratory season (19,350). A significant negative correlation was found between rainfall, water depth and bird population parameters. The highest number of birds was recorded during the replanting season and the sowing period of paddy. A significant negative correlation was also found between the paddy height and the abundance of birds. Shallow water was highly preferred among the 12 microhabitats. Species diversity Index (H’) was highest on the trees (3.44) and lowest on the bunds (1.38). Species density was highest in the shallow waters (67,788 birds/ha) followed by paddy fields (56,774 birds/ha) and mud flats (56,308 birds/ha). Highest niche breadth was recorded for Red-wattled Lapwing and Indian Pond-Heron. Mean species richness was significantly higher on the electric lines during dry season, wet-I season and in the mud flats during the wet-II season. Diversity Index (H’) was significantly higher on trees in the dry and wet-II season; during the wet-I season, this was higher on the electric lines. Mean density of birds was higher in the paddy fields in the dry and wet-II season and significantly higher in the floating vegetation during wet-I season. The Kole wetlands showed high species richness and abundance of birds, and are comparable to other wetlands and protected areas in Kerala. The Kole wetlands are an ideal habitat for migratory and resident birds, especially for the winter visitors. In the present study, 49 species of trans- continental migrants were recorded from the Kole wetlands, which showed the importance of the area as a wintering ground for migratory species. This wetlands supported waders similar to the known sites such as Chilika Lake, Pulicate Lake, Great Vedaranyam Swamp, Point Calimere and Gulf of Mannar. Among the four intensive study sites, highest number of birds was recorded from Kanjany, which can be attributed to the geographic position of the study site, which is in the middle of the Kole wetlands and for the high availability of mud flats. The increase in the wetland bird species from September to March in all the years reflected the availability of ideal microhabitats and higher production of benthic and macro fauna. The rainfa ll a nd the wa ter depth were the major climatic fa ctors influencing the abundance of birds at Kole wetlands. The area served many avian species for a wide variety of purposes such as nesting, roosting and wintering ground. Food and feeding behaviour studies of selected bird species showed that sufficient prey is available in the Kole wetlands and the selection of food depended on the variation in the feeding technique, body size and bill morphology. The study indicated a strong positive correlation between the wader abundance and the benthic fauna. The appearance of mud flats attracted large number of waders during the migratory season. As the Kole wetlands come under the ‘Central Asian - Indian flyway’ and one of the Ramsar Sites in India, protection of migratory bird species is of the highest priority.

 
1 Introduction

Birds possess great intrinsic interest, they are certainly among the most attractive population of all wildlife groups. Moreover, it is widely recognised that birds can act as valuable indicators of the quantity and quality for wildlife. The studies on avian communities attracted great attention over the past several years all over the world. Much of the early efforts emphasized on the patterns and processes in the avian communities and the listing of species. Previous workers mainly concentrated on the narrow perspectives and focused on single variables, but the recent studies have emphasised the necessity of multi- scale, multi-factor approaches and the inclusion of both short term and long-term temporal variables. The difficulties of assessing numerous variables and several scales, both temporal and spatial, seem to have discouraged the contemporary ecologists from embarking on studies on avian communities. The Western Ghats is well known for the wealthy and unique assemblage of flora and fauna and is one among the 25-biodiversity hot spots identified on the earth. Arising gradually from the narrow Konkan and Malabar coasts, these mountains run 1,600 km north south between the River Tapti in Gujarat and Kanyakumari in Tamil Nadu covering an area approximately equal to 1,60,000 km2. Kerala State, located between 8° 4’ and 12° 48’ N and 74° 52’ and 77° 37’ E is known for rich biological resources on account of availability of a variety of ecological niches and habitats ranging from lush tropical forest, valleys, plains and coastal areas.

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2 Species Composition of Birds

Species composition of birds in an area is related to the type of vegetation, height above the sea level, the availability of microhabitats and various other factors. The study site at Silent Valley covered all the representative habitats namely forest canopy, forest interior, forest edge, rocky patches, grass patches and foliage air interface met within a tropical forest. Riparian patches were excluded after an initial survey as it contained only a few species of forest birds. The Mukkali study site covered moist deciduous forest, burned forests, coffee estate, open rocky areas and agricultural land. Common species, Dominant species and Species richness of the two study areas were assessed and the data are presented in this chapter.

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3 Species Abundance Relations

In this chapter the data collected in Silent Valley and Mukkali on the abundance of birds are discussed. Species abundance relations of the community is also prepared and presented in this chapter. METHODS Abundance : Total number of birds seen in each month and seasons (summer and monsoon) were calculated using the census data. Density : Density of birds in each month, in two seasons and individual density of selected species were also calculated. The density was estimated using the line transect method (Burnham et al., 1980). The Fourier series method, which is used for analysis, is not dependent on specific distribution assumptions about the detection probability of birds at various perpendicular distances from the transect line. In this method density is computed from ungrouped, perpendicular distances from transect.

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4 Seasonal Changes of the Community

Tropical forests support a stable population of birds throughout the seasons in comparison to the temperate forests, where there is marked variation in tune with change of seasons (Wright, 1970). The seasonal changes of bird community at Silent Valley and Mukkali are presented in this chapter. There are two seasons namely monsoon (June to November) and summer (December to May). The availability of food at Silent Valley was studied to find out the relationship between seasonal changes of the community and the abundance of food.

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5 Vertical Stratification of the Community

Foliage diversity of a forest stand has an important role in providing food for tropical forest birds. This feature adds to the ability of tropical forests to harbour high bird diversity. Studies on forest bird communities mainly examined the parameters like structure of forest bird communities (Nilson, 1983); distributions (Howe et al., 1981) and community organisation (Landers and Mac Mohan, 1980). The pioneering, studies of Mac Arthur and Mac Arthur (1961) established the relationship between bird diversity and foliage density. Mac Arthur et al. (1962) and Mac Arthur et al. (1966) supported the above hypothesis. Some studies have showed negative relationship also (Wiens, 1983). Other vegetation characters, which have significant effect on bird diversity are foliage volume, percentage vegetation cover (Karr and Roth, 1971), percentage canopy cover (Crawford et al., 1981; Wiens and Rottenberry, 1981; James and Wamer, 1982). In India Ramakrishnan (1983) examined many bird community parameters at Silent Valley. Diversity and structure of birds were also studied by Johnsingh et al. (1987), Katti (1989), Daniels (1989), Sundaramoorthy (1991), Johnsingh and Joshua (1994), Gokula and Vijayan (1996). Even though many studies have been reported on the forest bird communities from South India, relation between foliage abundance and bird diversity have not been dealt in detail. The correlation between the abundance of birds in different height classes of tropical forest canopy with foliage abundance is reported in this chapter. The study forms part of a major investigation (Jayson, 1994), which determined many ecological aspects of two bird communities. Seasonal changes in these bird communities were reported earlier (Jayson and Mathew, 2000).

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6 Habitat Utilisation

In this chapter utilisation of habitat by the birds of the Silent Valley National Park has been analysed. Usually three questions are asked in the habitat utilisation studies (1) whether the species form well defined assemblages, quite apart from the geographical distribution patterns? (2) Whether ecologically or taxonomically similar species segregate by habitat? (3) Whether habitat characteristics attribute for the variations in the distribution or abundance (Wiens, 1989). METHODS Whenever a bird was observed in the period of study, its exact location and activities were recorded. The concept of habitat as described by Odum (1974), “the habitat of an organism is the place where it lives or the place where one would go to find it” is adopted for this study. Four main habitats were identified in the study area, depending on the vegetation type namely, Evergreen Forest (EF), Moist Deciduous Forest (MDF), Coffee Estate (CE) and Agricultural Area (AA). In each of the above habitats, “microhabitat” of birds was also recorded (Odum, 1974). Microhabitats identified at Silent Valley were the tree trunk, foliage, branch, bushes, dead tree, ground, grass and open area. Microhabitats identified at Mukkali were tree trunk, foliage, branch, bushes, ground, rocky areas and open area.

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7 Species Composition of Wetland Birds

Information on the avifauna of an area is a prerequisite to assess the status of birds and the habitat quality with specific attention to indicator species including the rare, endangered and endemic species. Birds are one of the best indicators of the health of an ecosystem. They are highly mobile and easily observed indicators of change in the environment (Holmes et al., 1986). Many wetland species also play a role in the control of agricultural pests, while some species are themselves considered pest of certain crops. After fish, birds are probably the most important faunal group that attract people to wetlands. Loss of wetland habitats through direct and indirect modifications and non-sustainable harvesting of water birds for human needs have led to decline in several water bird populations and a number of species (Jin-Han Im et al., 2001). Some of the most catastrophic declines of birds have taken place in the last few decades and the list of threatened species in the Asia- Pacific region has expanded rapidly to include species from a large range of water bird groups. While decline of some populations has been well documented, the fates of many others remain unknown. It is vital to understand the underlying causes in population changes and to attempt to control these trends in order to prevent key component of biodiversity of wetland habitat from being lost. The number of water birds using a particular habitat is related to types and quality of habitats, abundance and availability of food and level of disturbance. Monitoring of water birds can thus provide valuable information on the status of wetlands and can be a key tool for increasing the awareness of importance of wetland and conservation values. In this chapter, the status, occurrence and species composition of avifauna recorded from Kole wetlands are elucidated.

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8 Species - Abundance Relations

Number of individuals in a population increase under favourable environmental conditions. Sudden or violent changes in the environment or in the biological characteristics of the individual could lead to decline. Fluctuation in the population is usually because of the effect of a combination of several factors responsible for their survival, growth and reproduction. It is necessary to understand the cause of such fluctuations for better scientific management of the population as well as the habitat (Acharya, 2000). In most of the studies, community has largely been expressed in terms of species richness, abundance, density and diversity. All these have been used as indicators of habitat quality, because an increase in the value of the component is generally thought to reflect larger amounts of the necessary resources to sustain larger population within a given area. Moreover, it is believed that if the factors determining the distribution of the animals are known, predictions can be made concerning the responses of animals to specific perturbations and hence, such animals can be used to monitor environment quality (Gokula, 1998).

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9 Seasonal Changes of the Bird Community

Population studies have been traditionally used to monitor large scale, long term changes in avian population and to assess both habitat quality and the responses of birds to both management practices and natural and human caused environmental changes (Wiens, 1989). Species composition, abundance and behaviour of birds are known to vary seasonally (Morrison et al. 1980). Some species are permanent residents in an area, others occupy an area only during winter or summer months. In this chapter, seasonal variations of wetland bird community in the Kole wetlands are described in terms of species richness, abundance, diversity and density. METHODS Seasonal pattern The study area has three distinct seasons viz. dry season (December to April) wet-I, the period of southwest monsoon (May to August) and wet-II, the period of northeast monsoon (September to November). Based on the arrival of migratory birds, the months are divided into migratory season (September to March) and non-migratory season (April to August). Occurrence of birds in each month obtained through the daily census data was used for the seasonality analysis. Monthly changes and seasonal changes of the community were analysed. Species richness, abundance, diversity indices of each season and also in migratory and non-migratory season were calculated and presented. Population fluctuations of 36 wader species in the four intensive study areas during three migratory seasons were estimated. Apart from these, detailed information on the population fluctuation of selected bird species was presented.

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10 Habitat Utilisation of Wetland Birds

Habitat is the most valuable variable in ornithological studies as it provides food and cover essential for the survival of the population (White and Garrott, 1985). Habitat is an area containing or influenced by the suitable resources and environmental conditions that determine the presence, survival and reproduction of a population (Morrison et al., 1998). Cody (1985) described habitat as areas where an organism’s need for food and shelter are met. Habitat selection and use by birds is fundamental in understanding their biology and management and it has been one of the most well studied aspects of avian biology, particularly as habitats are altered by human activities (Pain and Pienkowski, 1996). According to the optimal foraging theory, animals may use the areas offering higher food extensively (Stephens and Krebs, 1987). By using the most productive patches, birds may have a high ingestion rate, allowing to reduce the time exposed to predators and having more time to other activities. However, some authors have obtained contradictory results also. They have not found clear relationship between bird abundance and food availability (Wiens, 1984 and Herrera, 1988). The ability to exploit food resources is one of the most frequently suggested reasons for habitat selection by birds (Caraco, 1980) and would be expected to be primary basis for selection of foraging habitat.

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11 Food and Feeding of Selected Species

Wetland birds serve an important ecosystem function of accelerating the nutrient cycling in the feeding grounds (Morales and Pacheco, 1986) and regulating fish populations (Miranda, 1995). According to Drent and Dann (1980), the availability of food is of primary importance to the birds during migration when, they store energy for winter survival and successful completion of migration. Many migrant shorebirds relay on a few key stopover sites to complete their annual migratory cycle (Myers et al., 1987), which provide a unique combination of food resources and habitat necessary to support these large numbers of birds (Myers, 1984). When animal species assemble at a particular area, they utilise individual but overlapping segments of the habitat (MacArthur, 1958). Karr (1980) stated that resource utilization pattern and the community organization are determined by a combination of variables. The availability and preference of the food organisms, feeding behaviour and utilization of the habitat for feeding and reproduction differ in co-existing animal species. Periods of rapid change in prey populations offer important opportunities to study the relationship between predators and their prey. In particular, such studies can yield information on the functional response of predators to a changing prey environment and the role of prey dynamics in the regulation of predator population size.

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12 Summary and Conclusion

Tropical forest bird community Species richness at Silent Valley and Mukkali were similar. Most of the birds at Silent Valley were sighted with in a distance of 4m during the census. At Mukkali this distance was up to 9m. Yellowbrowed Bulbul was the most common and dominant species found at Silent Valley. Most common species found at Mukkali was Black Drongo and dominant species was Jungle Babbler. A total of hundred and thirty-seven species of birds were recorded from the study area. There is no significant difference in bird species richness between years during monsoon and summer seasons at Silent Valley. But a significant difference in species richness is obtained between years in both seasons, at Mukkali. Four endemic and threatened species of birds were recorded from the study area. This shows the conservation value of the study area. Total number of birds sighted in each month showed significant difference at Silent Valley and Mukkali. This is due to the movement of birds influenced by the climatic and other parameters. Overall density of birds was high at Silent Valley (1122 birds/km2) and low at Mukkali (780 birds/km2 ). This indicates the ability of tropical evergreen forest to harbour more birds than tropical moist deciduous forest. The number of individuals/km2 recorded is comparable to other tropical forests in the world and from this observation we can also conclude that the study area is supporting a rich bird community.

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13 End Pages

Appendix Appendix 1. List of birds recorded from the Silent Valley National Park

 
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