Potentials of Owls as Agents for Controlling Rats and Mice Populations in Cultivations

Abstract

This report documents information about the population status of the barn bowl (Tyto Alba) and the little spotted owlet (Athene brama), their nesting and roosting habits in the cultivations of central Punjab. The main objectives of these studies had been to access the potentials of these two raptors in controlling the rats and mice and ended in June, 1999. During this period 47 localities in the districts of Faisalabad, Jhang, Okara, Sheikhupura and Hafizabad were visited for the collection of data on these owls. The pellets of the barn owl collected from Bahawalnagar (southern Punjab) and Usta Muhammad (Balochistan) were also examined. Wooden boxes and baskets were also installed in tress at different locations to provide nests/roosts to the owls. Cropland and non-crop habitats were sampled through snap-trapping to know about the abundance of the small mammals. Preferences and encounterability of some prey specifies were determined. Besides, the diversity for the seasonal and locality samples of prey items obtained from the examination of the pallets was computed. Barn owl Most of the barn owls were found living in the premises of the canal rest houses where they used hollows in the trunks and limbs of the old trees foe nesting and roosting. Of the 47 localities, 33 were found to be the positive for the owl. A total of 3336 pallets of the owl were collected from different localities. The house shrew was found to be the primary prey while the rats and mice, bats and birds served as secondary preys. Insects and amphibians were consumed only occasionally. The house shrew was the main item of the fall and winter diets whereas in the spring and summer diets, rats and mice birds and bats were better consumed. The diversity indices varied significantly from season to season (P<0.05). The same was found to be true for most of the locality samples. The food preferences and relative encounter values were the highest for the house shrew which was followed, in descending order of these values, by the pygmy shrew, the soft-furred field rat, the lesser bandicoot rat, the mice, the Indian gerbil and the house rat. Analysis of the sample of pallets from Bhawalnagar revealed that the house shrew was the chief staple of the diet of the barn own in that area too. But here the birds and the insects were consumed more intensively than by the central Punjab owls. In the pallets from Usta Muhammad (Balochistan), the soft-furred field rats and the mice were the main items whereas the house shrew had been relegated to the status of an unimportant secondary prey item. Birds and bats were eaten less intensively than in the former two study areas. Most of the nests and roosts of the barn owl were located in the tree hollows. The owl bred mainly during the fall and winter seasons. Only rarely breeding was recorded during the spring and summer seasons. The average yearly clutch comprised 7.7, 5.6, and 5.5 eggs and the average brood comprised 4.2, 4.1, and 4.0 chicks. Artificial nests (boxes/baskets) installed in tress at various localities were occupied by the owl sparingly; only about 12% (n=12) of these were used as nests or roosts. Human vandalism, disturbance and prejudice were found to be the cause for poor utilization of these nests. Little spotted owlet is common all over the low lands of Punjab where it occurs in good number in the rural as well as urban settings. A total of 745 pellets of this species were examined. Insects and small mammals viz. the mice, the soft-furred field rat were the chief components of the owlets’ diet. Birds were also eaten fairly intensively. The house shrew appeared in the diet of the owlet only occasionally. The preferences (a) and relative encounter (ei) values for the following mammalian prey items were the highest for the soft-furred field rat, which was followed in decreasing order, by the house mouse, the field mouse, the house shrew, and the Indian gerbil. The owlet mainly used tree cavities for nesting and breeding purposes. Unlike the barn owl it breeds during spring only. Most of the clutches comprised 3-5 eggs and the broods 2-4 chicks. The barn owls of the central Punjab heavily depend upon the house shrew for their food. As such their ability to suppress the rats and mice populations of the croplands fails to find its full expression. This problem can be overcome by providing perching posts creating clearings supplemented with rodent food, and installing artificial nests at appropriate places in the croplands. The most important hurdle in the way of promoting the owls’ predatory activities against the rodent pests is the highly negative attitude of man towards this raptor. The little spotted owlet do not suffer so much as do the barn owls at the hands of man. But the owlet is primarily an insectivore. However, because of its wide distribution and numerical superiority it apparently plays an important role in eliminating the mice and the soft-furred field rats. The barn owl deserves protection for its rat catching skills. Deplorably what little we know about the local population of this owl is nearly always overweighed by misconceptions, misguided notions and baseless traditional beliefs. On account of these reasons the owl ends up as much misunderstood creature, unjustly despised and relentlessly abused and persecuted. There is an urgent need for change in attitude vis-à-vis this useful bird. Our efforts to instill, among the people we met during the course of our field studies, the awareness that the owl was a useful bird had met with little success over the years. The mass media should be mobilized for educating the farmers and especially their children depicting the owl as friend and an effective enemy of rats and mice in the croplands. The house shrew is the chief staple of the diet of the barn owl in central Punjab. During the breeding season the owl meets most of its dietary requirements by eating this insectivore mammal. A vertebrate pest manager would want the owl to prey upon the pest rats and mice and not the shrew which is just a hangeron of man. Undoubtedly the value of the owl as a suppressor of rats and mice populations will greatly enhance if its dependence on the shrew for food was somehow minimized. This may be possible only when the former are made a more profitable source of nutrient than the shrews or alternatively, the owl may be introduced into where it is not present nor does the shrew compete with the rodents as its food. This can be achieved by bringing minor habitat alterations such an installations of perching posts creations of clearings, and installation of the nest boxes in the croplands so that the owl finds the rodents more profitable prey items than the shrews. The second proposal is for cultivations which are sparsely populated by man as well as the shrew (his hangeron), but are sufficiently infested with the rodents pests.