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This paper investigates the ecological linkages of the bird species of selected riverine habitats of River Ravi including the livestock of the sample area. Livestock is a source of revenue generation through low cost milk and meat production for the local community through free grazing. The insects in the pastureland that are dislodged by the livestock movement, are eaten by Cattle egrets, Bank mynas and Black drongos. Bank mynas and Black drongos were estimated to consume insects approximately one sixth of their body weight per day. However, Cattle egrets and Crested larks were found to consume insect biomass almost one third of their own body weight per day. The percentage of grasshoppers and beetles was found higher than other insects in the food of these birds. The quality of forage availability was linked to the number of grasshoppers present, affecting the milk and meat production of the area. The food plants, insects, birds, livestock, milk production and the economic benefits to the rural communities in these riverine habitats were found interlinked and interdependent.
Keywords: Riverine habitat, Ecological linkages, Insects, Livestock
A variety of bird species are found in the riverine habitats. Disturbance created by humans is continuously changing these habitats (Arscott et al. 2002). Clearing of natural riverine habitats for human settlements and agricultural activity is resulting in the loss of original habitats in addition to creating some new habitats. For the proper management of these new Riverine habitats knowledge of the ecological linkages of these habitats is needed. This study investigates the ecological linkages of the bird species and the socio-economical aspects in the selected riverine habitats of River Ravi. It also presents the feeding behavior of selected bird species.
Description of study areas
Three areas were selected for the study.
1. Balloki Headwork was constructed in 1913. Two canals, Lower Bari Doab canal and Balloki-Sulemanki link canal are fed from this Headworks (Ahmad and Chaudhary, 1999). River Ravi was a perennial river. Now its flow is highly variable depending on the use of its water in India after the Indus Water Treaty of 1960 (Ahmad et al. 1998). The old bed of a river is called "Beit". The width of the Beit of River Ravi varies between less than 1 km to 3 km within the study area. Due to construction of barrages and use of huge amounts of river water for agriculture, the flow of the river in non-flood season is confined to only a few shallow channels. The rest of the area usually becomes grassland and serves as free pastureland for domestic livestock. Marginal bunds were made to keep the flow of water permanently through the barrages. Additionally these bunds give protection from high floods to the surrounding villages, roads, canals and irrigation system. Spurs were also made with the bunds to protect these from possible damage of the high floods. The excavations for the construction of these bunds have lead to the formation of ponds, due to seepage or flood water. Wetland floral and faunal communities have established in these ponds. The river habitat has been degraded over the years, which has resulted in disappearance of wildlife such as Hog Deer, Fishing Cat and Smooth Coated Otter (unreported data, Manzoor, 2005). The palatable plants that grow in the Beit are heavily grazed by livestock. Most part of the Beit of the River Ravi has come under agriculture and human residence. However, there is considerable amount of milk and meat supply from these habitats. There is no scientific management of the Beit land to enhance livestock grazing capacity.
2. Siphon: The BRB canal crosses River Ravi through a siphon upstream of Lahore.
3. Mohlanwal: It is a village, located 28 km south of Lahore along the river. Hudiara drain falls into River Ravi just before Mohlanwal village (near Khurdpur village) and water here is nothing but foul odour water.
MATERIALS AND METHODS
Six visits were made to Balloki Headworks, five in the months of April, May, June, July and November 2005 and one in October 2006. Three visits were made to Siphon, two in April and one in December 2005. Two visits were made to Mohlanwal village, one in May 2005 and the other in January 2006. Bird observations were made using binoculars. Birds were identified in the field using field guide. A total of 59 specimens of four bird species were shot during November 2005 to October 2006 from Balloki Headworks. These were Cattle egret Bubulcus ibis, Bank myna Acridotheres ginginianus, Crested lark Galerida Cristata and Black drongo Dicrurus macrocercus. These were immediately weighed with an electronic balance. Food in the crops was scooped out after these were removed from the body. Weight of samples was measured with an electronic balance. Preservation of samples was done in 10% formaldehyde. Identification of the food contents was got done by an entomologist. To figure out average daily food consumption, the average food consumed in one hour was multiplied by activity hours of the birds. For Cattle Egret, Black Drongo and Bank Myna six hours of activity were taken. Non-grazing time was not included i.e. only six hours of grazing period was considered. For Crested Lark, ten hours of activity were taken.
Insect sampling: To find out the percentage of insects in the habitat, sampling was carried out by Sweep Net of 0.5mm mash size, up to 3 km upstream of Balloki Headworks. Six samples were collected from 100m long and 1.5 meter wide area. Insects were preserved in 10% formaldehyde for identification.
Plant sampling: Plants growing on the eastern and western sides of the river water channels were collected from Balloki Headworks. Sixteen circular quadrates of 11.8 ft (0.01 acre) radius were made with the help of a string on both sides. In total thirty-two circular quadrates (0.32 acres = 0.12 hectare) were made. The distance between the centers of two quadrates was estimated to be 20 meters. Plants were collected and identified by a plant taxonomist.
Relative abundance: Relative abundance of birds and plants was calculated by using the following formula:
Relative abundance = Total Number of individuals of a species in all quadrates x 100
Total Number of individuals of all species in all quadrates
In total thirty-two species of birds were counted at Siphon, forty-seven from Balloki Headworks and twenty-six from Mohlanwal from 2005 to 2006. Yellow wagtails were found in abundance at Balloki Headworks. Its Relative abundance was calculated to be 33.8, that of House martin 31.1, White wagtail 16.2, Common myna 4.72 and Cattle egret 4.47. The Relative abundance of Purple sunbird was 8.75 which was the highest at Siphon as compared to Balloki Headworks. Relative abundance of Little green bee eater was 6.49, Blue tailed bee eater 5.08 and of Short-toed lark, Little brown dove and Common Myna 4.51. Relative abundance of Bank Myna was 21.2 at Mohlanwal Village, Common Myna 8.8, Blue tailed bee eater 7.6 and of Red wattled lapwing was 7.2. Complete list of species observed with their relative abundance in all three selected habitats is given in Table 1.
Socio-economics of the Study Area
Kana Saccharum bengalense is a source of income for the government, local communities and traders. It is harvested each year from the last week of December to February to make reed screens locally called "Sirkee". These are used as thatching material in villages as well as for fuel in the local communities of Balloki Headworks. Approximately 150 people are involved in the Kana business. Eighty to one hundred bundles of Kana are obtained from one acre land. The bundle is locally called "Pula" and one Pula contains 200 Kanas. Price of one bundle is Rs.70 -100. One Sirkee is 8-12 feet wide and 15ft long, which is sold at about Rs 1½ to 2½ per square foot. One acre crop of Kana is sold for Rs.10,000. One person makes upto 50-80 ft sirkees in one day and earns up to Rs. 200-250 per day (noted in 2006). The proportion of males and females involved in sirkee making is 30% and 70% respectively. The place where Kana is sold is called "Jhatharee ada''.
Tamarix is used for making baskets. Commercial over exploitation of Tamarix has almost eliminated it from these habitats. Five acres of Tamarix was estimated in Balloki Headworks while traces of degraded Tamarix were observed on the bank of River Ravi at Ravi Siphon, at about ten acres.
Dib Typha domingensis provides roosting site to birds especially the transit migrants. In 10 hectare area of Typha, roosting of more than 60,000 wagtails, martins, weaver birds and 8000 black starlings was observed on May 8, 2005. It is a source of income to government and the local communities. More than 70% of Typha is harvested each year from mid September to mid November for handmade mats. It is annually auctioned by the government (unreported data, Manzoor, 2005).
In all 19,000 buffalos, 12,000 cows, and 25, 00 goats/sheep graze within 3km upstream of Balloki Headworks. It was estimated that on an average, 1,050 buffalos from the western side produce 8,400 liters of milk while 1,800 buffalos from the eastern side produce 14,400 liters milk per day. This milk is sold for rupees 14/liter only. For cows it was estimated that about 75% produce milk while 25% do not produce milk. On an average, 3000 cows from the western side produce 9,000 liters of milk while 6,000 cows from the eastern side produce 18,000 liters of milk per day. This milk is sold for rupees 13/ liter. Out of 2,500 goats/sheep only about 20% are sold during the year while remaining 80% are sold at the time of Eid ul Azha.
Livestock grazing in Mohlanwal habitat was estimated to be: cows 2,000, buffalos 300 and sheep /goats 400-500. Total 1,000-1,200 liter milk per day was produced by the livestock and was transported to Lahore.
Food Analysis Study
Food analysis of fifty-nine specimens of four bird species (Cattle Eeret Bubulcus Ibis, Bank myna - Acridotheres Ginginianus, Crested lark - Galerida Cristata and Black drongo- Dicrurus Macrocercus) was studied with special reference to the livestock at Balloki Headworks from November 2005 to October 2006.
Cattle egret: Analysis of crop contents of six Cattle egrets was done from the samples taken on November 26, 2005. (24°C) between 5pm to 7pm. Average weight of Cattle egret was 440gms. Insects were prominent in their diet. These included grasshoppers, chrotogonous, beetles, mole crickets, mouse and a young frog were recorded (Figure 1). Food intake of six Cattle egrtes is given in Table I.
Bank myna: Analysis of crop contents of thirty-seven Bank mynas was done by the samples taken on May 19, 2006. between 7.30-11.30am (32°C). Twenty specimens of Bank myna had consumed seeds, lepidoptera larvae, beetles, grasshoppers, field crickets and cockroaches (Figure 2). Four crops were empty while thirteen had unidentifiable material but no insects or seeds (Table II).
Black drongo: Analysis of crop contents of eleven Black drongos in samples taken on June 8, 2006. (41°C) showed body parts of grasshoppers, rice grasshoppers, body parts of cricket and mole cricket (Figure 3). Food intake of Black Drongos is given in Table III.
Crested lark: Analysis of crop contents of five Crested larks was done by the samples taken on October 2, 4, 7 and 8, 2006. between 8am to 1.30pm. Crested larks consumed seeds, beetles and dragonflies (Figure 4). Food intake of Crested larks is given in Table IV.
Plant Sampling was done 3 km upstream of Balloki Headworks to estimate the palatable grasses present at Balloki Headworks. Plant samples were collected from 0.32 acres (0.12 hectare) plots. Plants collected in the sample included, Poa annua, Oxalis esrniculata, Sissymbrium irio, Ranunculus muricatus, Cannabis sativa and Fumaria indica.
Sweep net was used to find the population of insects in pastureland at Balloki Headworks. Grasshoppers were present in large proportion 60%, 12% beetles, 11% spiders and 8% ants.
Most of the human settlements in the study areas were found economically linked to the livestock, agriculture and aquatic flora growing along the peripheries of the ponds.
The ecological and socio-economic values of Kana Saccharum bengalense were studied. Kana Saccharum bengalense was estimated to be found in approximately eighty acres in Balloki Headworks study area. It was used for making sirkee which is used for thatching roofs of houses in villages. It provides nesting and roosting places for many bird species such as Pied bush chat, Indian prinia, Black drongo, Common babbler and Jungle babbler. In February, Kana is set on fire to burn its leaves to make its harvesting/cutting easy. As a result some nests, eggs and nestlings of early breeding birds are lost. Insects are burnt along with the burning of Kana, which are the food of Black starlings and Black drongos.
A large proportion of Cattle and Buffaloes graze in the selected habitats. In Balloki Headworks only 15% buffaloes produce 8 liter milk/buffalo /day. 75% cows produce 3 liter milk/cow/day which is sold at cheap rates. Due to free pasturing and almost nil stall feeding of milk dairy livestock and calves, the milk and meat production cost was not high. Moreover grazing was usually by one or two persons per heard.
Food analysis study revealed that all birds were mostly insectivorous. Insects dislodged by movement of grazing animals were caught by these birds. Most insects found in food of bird species were vegetation eaters such as grasshoppers and larvae.
Cattle egret is ecologically linked to grazing cattle. These were seen in close association with cattle at Balloki Headworks. The number of Cattle egrets observed with grazing cattle varied but averaged three to four per animal. Egrets move very near to the cattle, picking insects from the grass when disturbed by the feet of grazing cattle. Similar behavior of Cattle egret was documented by Snoody (1969), Akhlaq (1971), Ali,S. (1979), Whistler (1986), Robert (1992) and Fogarty and Hetrick (1993). Cattle egrets that associated with cattle in the study area caught prey items at a faster rate and apparently consumed less energy to achieve this (Seedikkoya et al. (2005). This association appears to be an example of facultative commensalism (Rand 1954, Heatwole 1965). Previous studies by Ikeda(1956), Snoody(1969), Akhlaq(1971), Ali,S.(1979), Whistler(1986), Robert(1992) and Fogarty and Hetrick (1993) reported Cattle egret to be an insectivorous bird. In a similar study done by Mukerjee (1971) stomach analysis of 318 birds collected from West Bengal in the Sunder bans revealed mainly an insect diet. While in another study done by Fogarty and Hetrick (1993) in Florida revealed that nearly 90 percent of the foods identified from 841 stomachs were common pasture insects varieties likely to be disturbed by cattle. It was estimated that an Egret weighing 440gms consumes 22.5gms of insects in one hour. In six hours of activity it might consume 135gm of insects. On average an Egret weighing 440gms may consume almost one third of its own weight of insect food.
Bank myna was observed to be ecologically linked to domestic livestock (cows and Buffaloes). These birds feed mostly on ground, searching for the insects. It rides or follows grazing livestock to get benefit of the disturbance caused to insects by animal hooves. Similar behavior of Bank myna has been documented by Ali and Ripley (1983), Robert (1992) and Masood (2004). In studies by Mason and Lefroy (1912) stomach contents of eight birds in Bihar (north central India) were collected in late June and late August and found the birds to be insectivorous. Insect remains were largely recovered. Presence of insects and seeds in the diet of Bank myna has been previously documented by Ali (1979), Robert (1992) and Ishfaq (2001). The feeding behavior of Bank myna comprises of variety of materials increasing the chances for this specie to exploit all habitats. Mynas were observed finding and eating roasted insects from ashes after the reed fire. It was estimated that Bank myna weighing about 73.7g consumes 2.12g of food in one hour. In six hours of activity it might consume 12.7g of insects. Thus consuming the insect food averaging about one sixth of its body weight.
Black drongo is a bird of open country, usually perching on telegraph wires or attending the grazing cattle. It rides on the backs of grazing cattle and dives to eat flying insects disturbed by the cattle movement. Many Black drongos were observed feeding on flying insects as the reeds were set on fire. Larger insects such as grasshoppers, crickets and dragonflies are first dismembered and then eaten (Robert, 1991 and Ali,S 1979). Studies by Akhlaq(1971) and Robert (1992) also mention that this specie mostly consumes insects. It is reported to be highly beneficial to agriculture by the vast quantities of injurious insects it destroys (Ali, 1979). Mason and Lefroy (1912) also found that Black drongo consumed insects, which included grasshoppers and mole crickets in the largest proportion. It was estimated that on an average the Black drongo weighing 51g consumes 1.3g of insects in one hour. In six hours of activity it might consume 7.8g of insects. A Black drongo weighing 51g may consume at least one sixth of its own weight of insect food (The digested food during one hour was not included). The body and its juices weigh at least four times the weight of legs, wings, head etc of an insect. Therefore, 1.3g of undigested matter means at least five grams of digested food in one hour. That means a 51g Black drongo consume atleast 30g of insects in a day.
Crested lark is an insectivorous bird found in barren land where cattle graze. It feeds on the ground while running rapidly and stopping suddenly to capture insects with beak on grassy areas and beneath stones. They hunt in the vicinity of animal farms from village to village pecking at the dung of domestic animals (Whistler (1986), Salim Ali (1979). The food analysis has shown the presence of seeds in the diet of Crested lark which have been previously documented by Akhlaq (1971), Ali (1979) and Robert(1992). It was estimated that Crested lark weighing 25.1g consumes 0.9g of insect food in one hour. In ten hours of activity it might consume 9g of insects. Thus consuming insect food on the average almost one third of its own body weight.
Relative abundance of the plant samples collected showed that Cynodon dactylon (Bermuda grass) was present in highest percentage which is a palatable grass (Husnain and Usmani, 2006). Kahi Sacchrum spontaneum, Maize, Kikar Acacia nilotica, Ber Ziziphus mauritiana and cherry were also used as fodder at Balloki Headworks. Additional fodder was given to the livestock in Mohlanwal village.
The insect samples showed that grasshoppers were present in the largest proportion in the pasture land of Balloki Headworks. The grasshopper eats the blades of the grass usually from the lower part or middle waste to the ground, thus causing damage to the vegetation. It eats almost equal to its own weight per day.
Grasshoppers cause considerable damage to the forage species of plants. This results in reduction of forage for livestock, consequently affecting the milk and meat production of the area. Four bird species (Cattle egret, Bank myna, Black drongo, Crested lark) are linked to the livestock and insects for their diet. The insects are linked to the vegetation in the study areas, while if the population of insects increases, it will adversely affect the grasses upon which livestock graze. This is likely to affect the livestock resulting in reduction of meat and milk supply in the area, adversely affecting the local community.
Thanks are due to my supervisor, Prof. Z.B Mirza for guidance in the field research, to Dr. Abdul Aleem Chaudary for critically reviewing the manuscript, to Mr. Shahid Iqbal for helping in the fieldwork, to Professor Shamshad Zoology department (GCU) for identification of insects and to Professor Zaheer-ud-Din Khan Botany department (GCU) for identification of plant samples. We are also grateful to World Wide Fund for Nature Pakistan (WWF-P) for major funding of this research.