0 Start Pages
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.