INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, Copyright 2010 All rights reserved Integrated Publishing Association

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1 INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011 Copyright 2010 All rights reserved Integrated Publishing Association Research article ISSN Breeding biology of the Spotted Owlet (Athene brama Temminck, 1821) in Madurai district, Tamil Nadu, India Department of Zoology, Saraswathi Narayanan College, Perungudi, Madurai, Tamil Nadu, India ABSTRACT Breeding biology of the Spotted Owlet (Athene brama) were studied during the breeding seasons from January to April 2008 and 2009 in Madurai District, Tamil Nadu, India. Of the 32 nest sites located, the Spotted Owlet largely preferred holes/cavities found in trees, highest numbers of nests were located in Ficus benghalensis, rather than other sites for nesting. Nestsites were found at a mean height of 13.3 ± 5.44m above the ground, diameter at breast height averaged ± 22.49cm and nest hole location height averaged 6.9 ± 1.92m above the ground and the mean height, width and depth of nest holes/cavities were 34.5 ± 10.42cm, 24.9 ± 9.24cm and 80.9 ± 15.74cm respectively. Clutch size varied between 2 and 5 with a mean of 2.6 ± 0.72 eggs. The maximum and minimum length and width of eggs were 31.0 x 23.0mm and 26.0 x 20.0mm respectively. Weight of the eggs varied between 10.0 and 17.0g. The mean incubation period of the Spotted Owlet was 26.2 ± 1.31 days and both sexes took part in incubation. The hatching and fledging success of the Spotted Owlet were 83% and 71%, respectively. Keywords: Spotted Owlet, Nest site, Eggs, Incubation, Madurai 1. Introduction The Spotted Owlet (Athene brama, Aves: Strigidae) is a common resident raptor found all over India. There are three sub species viz., Athene brama brama, Athene brama indica and Athene brama ultra known to occur in India. The nominate form is known to occur in South of 20 N latitude (Ali and Ripley, 1969). Spotted Owlets are mainly nocturnal and roost in the day under thick shady vegetation, cavities in trees, man made structures including functional or non functional irrigational wells and crevices found in rock cliffs. Though a handful of information is available on its dietary composition (Jain and Advani, 1984; Kumar, 1985; Jadhav and Parasharya, 2003; Pande et al., 2004, 2007), very little is known on their breeding habits and their nest site characteristics. However, Ali and Ripley (1969) and Kumar (1985) briefly described the distribution and breeding biology of this species in India. In this paper, fist time we provide some detailed information on the breeding biology of the Spotted Owlet in Madurai District, Tamil Nadu, India. 2. Materials and Methods 2.1 Study area The present study was carried out in Madurai District (9 30 Ń, É), Tamil Nadu, India from 2008 to The mean monthly maximum and minimum temperatures during the study period ranged between 33.6 C (range 29.1 C 36.9 C) and 22.8 C (19.7 C 25.1 C) Received on April 2011 Published on June

2 respectively. The major precipitation of the study area is north east monsoon which usually brings rain during October December and the hottest season occurs during April June. The precipitation and other climatological factors of the study area seem to be erratic and discontinuous locally. Although paddy is the predominant cultivated crop in the study area, other crops such as sugarcane, banana, jasmine, betlevine, groundnut and sorghum are also being cultivated in different portions. 2.2 Nest site and nest location height Nest site and nest location height above the ground were measured by using an altimeter. 2.3 DBH and basal circumference Diameter at breast height (DBH) and the basal circumference of nesting tree was measured with a standard measuring tape. 2.4 Number of primary branches Number of primary branches in each nesting tree was counted visually. 2.5 Canopy volume Canopy volume was calculated using the following formula V = 4/3 π (D/2) 3 Where, V = Volume of canopy; D = Diameter of crown Mean crown diameter was estimated by averaging the measurements of four canopy cover estimates (north, east, south and west) around the nest trees. 2.6 Number of cavities Number of cavities in each nest site was counted visually. 2.7 Distance to nearest microhabitats In order to quantify the factors determining the nest site preference the following ecological variables viz., the distance from each nest to the nearest tree, agricultural lands, fallow lands, water sources, groves, human habitations, building, road, foot path, electric line and light source was measured around 500m radius centered at each nest site. The radius of 500m was chosen because the Spotted Owlets usually forage near the nest sites within this range (Pande et al., 2004). 2.8 Nest dimensions The hole/cavity height and width was measured by a centimeter scale or standard tape. Cavity depth was measured from the cavity entrance to the bottom of the nest by a centimeter scale or tape. The thickness of tree wall at hole was measured by using a Vernier caliper (Nagarajan, 1998). 1683

3 2.9 Eggs The length and width of egg was measured with a Vernier caliper and weighed to the nearest 500mg with a spring balance. The egg shape index (ESI) was computed by using the formula breadth x 100 / length (Prasanth et al., 1994) Clutch size The number of eggs in each nest was enumerated for clutch size Incubation and chick rearing period The incubation period was determined from the date in which the first egg was laid till the first egg hatched. The chick rearing period was interval between first day of chick and date in which the first chick fledged from the nest Brood size Number of nestlings present in each nest was considered as brood size Hatching and fledging success The hatching success (Balant, 1993) and fledging success (Dabert, 1987) was calculated by using the following formulas Hatching success (%) = No. of eggs hatched / Total no. of eggs laid x 100 Fledging success (%) = No. of nestlings fledged /Total no. of nestlings hatched x Statistical analysis Basic statistics such as arithmetic mean and standard deviation were calculated for all the replicate variables and are given as mean ± SD. Student t test was used to compare the means of two different groups of data. Principal Component Analysis (PCA) was performed on the nest tree characters to determine the most important factors in delimiting the habitat preference of the Spotted Owlet. The multiple regression equation was use to test the any relationship between nest dimensions (length, width and depth) and clutch size. The statistical software MINITAB (version 13.1) was used for data analysis. Results are reported as significant if they are associated with a value p<0.05. Statistical inferences were made by following Sokal & Rohlf (1981). 3. Results A total of 32 nests was located and monitored during the entire study period: 12 in 2008 and 20 in The breeding activities of the Spotted Owlet were found between 6 th January and 26 th April throughout the study period. It was observed that the Spotted Owl performed only one brood per year. Most of the egg laying took place from the early January (29 nests) through February. The young ones were recorded mostly in mid March and fledglings were recorded in late April. Of all the nests, 27 of them were found in trees and the remaining was 1684

4 in man made structures including one in wooden nest box. The trees used by the Spotted Owlet for nesting were Ficus benghalensis (48%), Enterolobium saman (30%), Cocos nucifera (15%) and Tamarindus indicus (7%). Table 1: Nest site and habitat characteristics of Spotted Owlet in Madurai District, Tamil Nadu, India Variables Total height of nest site (m) Height of nest location (m) Diameter at breast height (cm) Basal circumference (cm) Canopy volume (m 3 ) Total number of primary branches Height of first branch Number of holes or cavities / nest site Distance to nearest tree (m) Distance to nearest agricultural lands (m) Distance to nearest fallow lands (m) Distance to nearest water sources (m) Distance to nearest groves (m) Distance to nearest human habitations (m) Distance to nearest building (m) Distance to nearest road (m) Distance to nearest footpath (m) Distance to nearest electric line (m) Distance to nearest light source (m) Nest site characteristics Range Mean ± SD ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 4.69 The mean nest site height and nest location height above the ground, and the mean DBH of nest tree were 13.3 ± 5.44m, 6.9 ± 1.92m and ± 22.49cm respectively (Table 1). Among the 11 micro habitat variables estimated around each nest site, at least seven variables such as distance to nearest tree, building, footpath, electric line, light source, groves and water sources were very closer (<100m) to the nest site (Table 1). The Principal Component Analysis (PCA) resulted in the extraction of three main components which accounted for more than 81% of the total variance. The first component was highly associated with nest tree height, DBH, canopy volume and distance to fallow lands. The second component was associated with nest location height, basal circumference, height of first branch and distance to agricultural lands. The third component was highly associated with variables viz., canopy volume, total number of branches and distance to light source (Table 2). Nest dimensions were measured for 29 nests which had the following mean dimensions: cavity/hole height: 34.5 ± 10.42cm (range: 8 59cm), cavity/hole width: 24.9 ± 9.24cm (range: 6 45cm), cavity/hole depth: 80.9 ± 15.74cm and thickness of tree wall at hole: 3.7 ± 1.85 (range: 1.9 8cm). 1685

5 Table 2: Principal components derived from the nest tree variables of Spotted Owlet in Madurai District, Tamil Nadu, India Variables Nest tree height Nest location height DBH Basal circumference Canopy volume Total No. of branches Height of first branch No. of holes Distance to nearest tree Distance to nearest agricultural lands Distance to nearest fallow lands Distance to nearest foot path Distance to nearest water sources Distance to nearest groves Distance to nearest human habitations Distance to nearest building Distance to nearest road Distance to nearest light source Principal Components PC I PC II PC III Explained variance (%) Cumulative percent variation explained Note: Underlined values represent high correlations with the respective principal components Table 3: Clutch and brood size and nesting success of Spotted Owlet in the study area Clutch size Brood size Year N 1 Mean ± SD Mean ± SD Nesting success ± ± ± ± 0.76 (83%) (95%) Total ± ± 0.91 (91%) 1 A nest was defined as an active nest with at least one egg 2 A successful nest was one that fledged at least one nestling 1686

6 Table 4: Hatching and fledging success of Spotted Owlet in the study area Year Total No. eggs laid No. eggs hatched Hatching success (%) No. young fledged Fledging success (%) % recorded Eggs 3 Eggs 4 Eggs 5 Eggs Clutch size Figure 1: Clutch size (N=32) variations of the Spotted Owlet in the study area Spotted Owlet eggs were roundish oval and appeared milky white color without any markings. Clutch size varied from 2 to 5, with an overall mean of 2.6 ± 0.72 (Table 3). More nests had two egg clutches (53.1%) than others (Figure 1). The multiple regression analysis inferred that no correlation between nest dimensions and clutch size (r=0.7801; p=0.859; df=31). Eggs averaged 26.8 ± 1.89mm in length (range mm; N = 82), 22.9 ± 1.61mm in width (range mm; N = 82) and 13.6 ± 1.47g in weight (range g; N = 82). The egg shape index value ranged between 75.0 and 91.6 with an overall mean of 85.3 ± Incubation started after laying the first egg and the mean incubation period for all clutches (n = 18) was 26.2 ± 1.31 days (range days). Both partners involved in incubation. During incubation, while one bird incubates, the other partner either male or female perches nearby the nest within the vicinity and watching over the nest. The mean brood size for the two years together was 2.1 ± 0.91 (Table 3). Brood size of two was very common (43.75%) and no significant differences was noticed between years (t 17 = 0.540, p = 0.297). More than 90% of the nests were successful (Table 3) of which 100% success were found in 20 nests. Of the 82 eggs laid in 32 clutches, 68 eggs hatched (2.1 ± 0.90 eggs / nest) and thus gave a mean hatching success of 83% (Table 4). There was no significant difference (t 23 = 0.444; p = 0.482) in hatching success between years. A total of 48 nestlings fledged (1.5 ± 0.72 nestlings / nest) which yielded a mean fledging success of 71% (Table 4). The fledging success 1687

7 significantly differed (t 21 = 2.513; p = 0.042) between years. The weaning period ranged between 30 and 33 days and 90% of the nestlings fledged after 30 days. 4. Discussion The Spotted Owlet breeds during January to April as reported by Mahmood ul Hassan et al., (2007) and Pande et al., (2007) elsewhere. Spotted Owlet produced only one brood per year and no second brood or replacement of brood was noticed in the present study. Spotted Owlet used mostly tree cavities and holes found in buildings and man made wooden nest boxes for nesting. Kumar (1985) reported that nearly 57% of the Spotted Owlet nests were in tree holes in Andhra Pradesh, India. Pande et al., (2006) found that 26.8% of nests were in tree holes, who have recorded nests in holes of abandoned buildings, wall under a bridge and wells. Pande et al., (2007) stated that in human related area, the Spotted Owlet used cavities in human made structures, while in open country they nest in existing cavities in trees. Naik (2004) reported that Spotted Owlet readily accept and occupy nest boxes for nesting. In the present study intraspecific competition between Spotted Owlet and other cavity nesters viz., Common Myna (Acridotheres tristis) and Indian Roller (Coracias benghalensis) were recorded. Trees used for nesting in the present study were Ficus benghalensis, Enterolobium saman, Cocas nucifera and Tamarindus indicus and 96% of all trees were alive. The trees used by the Spotted Owlet (Ficus benghalensis, Enterolobium saman, Cocos nucifera, and Tamarindus indicus) were common, large, well branched, densely foliaged trees and therefore provide more suitable nesting cavities/ holes to the Spotted Owlet. Pande et al., (2006) reported that six tree species viz., Ficus religiosa, Tamarindus indicus, Mangifera indica, Ficus benghalensis, Moringa oleifera and Melia azaderach were used by the Spotted Owlet in Maharashtra, India. Mahmood ul Hassan et al., (2007) observed that Spotted Owlet nests in Dalbergia sissu, Acacia nilotica, Butea monosperma, Ficus benghalensis, Mangifera indica and Eucalyptus citriodora in Pakistan. The variation in species composition of nest trees in other region suggests that the preference is primarily based on the availability of suitable cavity to accommodate their young ones rather than tree species. Mean nest site height, nest height and tree DBH in the present study were greater than other studies (Pande et al., 2006; Mahmood ul Hassan et al., 2007). The considerable variation in these parameters in different regions suggests that size of the tree or heights of the nest are relatively less important in nest site preference than the presence of a suitable cavity/hole. Tome et al., (2004) stated that presence of predators as the main factor to nest site preference by Little Owl (Athene noctua). Schonn (1986) and Rendell & Robertson (1989) reported that avoidance of predators is one of the most important factors involved in the nest site preference of owls and other cavity nesting species. In the present study no predators were identified except some human disturbances. The study indicated that habitat such as agricultural lands, groves, human habitations; buildings and light sources were closer to the nest sites. These habitats provide more profitable high energy foods such as rodents, insects, lizards, etc. during breeding season to feed the growing young ones. In the study area, mean cavity/hole height, width and depth were 34.5cm, 24.9cm and 80.9cm respectively. In Maharashtra, Pande et al., (2006) observed that the horizontal depth of nest tunnels in earth cuttings in wells or in banks were about 45cm and vertical depth of holes in 1688

8 trees was up to 60cm. No other data in relation to nest dimensions of Spotted Owlet is available in India to compare our results. The mean length and width of the 82 Spotted Owlet eggs in the present study were 26.8mm and 22.9mm respectively. The morphometric measurements of Spotted Owlet eggs were comparatively less when compared to the descriptions of Ali and Ripley (1983) and Jadhav & Parasharya (2003). In contrast to length and width, the weight of Spotted Owlet egg was significantly greater values (13.6g) than in Maharashtra (Jadhav and Parasharya, 2003) and lower than the Andhra Pradesh (Kumar, 1985). The mean clutch size of the Spotted Owlet in the present study (2.6eggs) is similar to the values reported by Mahmood ul Hassan et al., (2007) in Pakistan. Several factors might contribute to clutch size variability viz., condition of the breeding female, availability of resources necessary to produce eggs, time of laying in the season, anticipated future availability of food for feeding nestlings and natural calamities (Lessels and Krebs, 1989; Stinson & Stinson, 1994; Asokan et al., 2009a, b). The mean brood size of the Spotted Owlet in this study (2.1 young) is lower than in (3.3 young) Pakistan (Mahmood ul Hassan et al., 2007). The overall hatching success in the present study was 83%, and this is more or less similar values obtained by Mahmood ul Hassan et al., (2007) in Pakistan. During the study period, out of 32 nests studied, 20 nests yielded 100% fledging success with an overall fledging success of 71%. The unusual rainfall during April 2008 and 2009 caused 100% nesting failure in three sites. However, various factors like suitable nesting sites, temperature, moisture and predators may also influence the nesting success of the Spotted Owlet. Acknowledgement Authors are thankful to the Ministry of Environment and Forests, Govt. of India, for providing financial support for the presnt study. We are grateful to Principal and Management of Saraswathi Narayanan College (Autonomous), Madurai for having rendered facilities and encouragement. We acknowledge the valuable comments to this manuscript by Dr. V. Gokula, Assistant Professor, Dept. of Zoology, National College, Trichy, India. We are thankful to Mr. P. Muthukumar, Field Assistant, for accompanying with us during the field trips. 5. References 1. M.A. Aziz. (1995). A Textbook of Engineering Materials, 1 st edition. 2. Ahmed, S., Iqbal, Y., Ghani, F. (2008). Phase and microstructure of brick clay soil and Fired Clay Bricks from some areas Peshawar Pakistan, J Pak Mater Soc, 1(2), pp Ali, S., Ripley, S.D. (1969). Hand Book of the Birds of India and Pakistan. Vol. I. Oxford University Press, London. 2. Ali, S., Ripley, S.D. (1983). Hand Book of the Birds of Indian and Pakistan. Oxford University Press, London. 1689

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