Browsing by Author "Mohan, D."

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A Study of Resource Seletion by Black Kites (Milvus migrans) in the Urban Landscape of National Capital Region India
(Wildlife Institute of India, Dehradun, 2013) Kumar, Nishant; Mohan, D.; Jhala, Y.V.
Black Kites are the scavenger and predator raptors of the old world. In India they are synanthropic and perform the ecological role of city scavengers. Abundance and distribution of these birds suffers change due to rapid infrastructural changes in the developing cities which likely limit or change spatial layout of the available habitat and food. Many cities in the old world (London, Cape Verde, Istanbul) have experienced decline in the population of Milvus kites owing to rapid urbanization. Indian sub-continent almost lost its main scavenger, white backed vultures, in the last century. After this loss; existence of black kites, the most abundant raptor of the old world proves very vital. On these lines I carried carry out this dissertation from December 2012 to April 2013. This study focused on a) estimating the abundance of Black Kites on the Ghazipur dump site and the abundance of nesting pairs in National Capital Region (NCR), b) evaluating factors influencing nesting habitat selection combined with a broad understanding of its foraging habits and c) estimating nest survivorship in the urban landscape. I studied these parameters at selective study sites in NCR by intensive counts of birds at Ghazipur and breeding pairs at nest sites across eight study sites. Nests were searched intensively at each site while I tried to develop and test a new method to count the kites on the Ghazipur dump. Data from 116 nests and nest sites covariates were used to model nest survivorship under Known Fate scheme in Programme MARK. For my first objective, I estimated the current abundance of nesting pairs of Black Kites at 7 study sites. It ranged from 4 pairs / km2 in Sagarpur to 67 pairs / km2 in North Campus area. Nesting kites were selective while choosing a nest site, as evident by significant partial correlation between nest density, food index and green cover. The sites at the best trade-off between green cover and food availability had the highest nest densities. While developing a new methodology, I estimated around 2400 kites on the Ghazipur dump. Through behavioural observations and broad examination of regurgitated pellets, I could confirm scavenging as well as predacious nature of Black Kites. The overall probability of a nest to produce a viable fledgling was 0.45. The nest survivorship was stage specific and varied with pre-laying, incubation or nestling stage. The lower survival probability (0.60) at pre-laying stage is likely because of surplus nest formation at sites with good foraging opportunities. Understanding the importance of kites in urban ecology, studies using individually marked birds will reveal vital details of their behavioural and physiological adaptations. If future long term studies are conclusive enough, may establish Black Kites as an umbrella species of urban ecology.
A Study on Breeding Behaviour of Oriental White-backed Vulture (Gyps bengalensis) in Anjarle and Deobag, Mahashtra
(Wildlife Institute of India, Dehradun, 2011) Kambale, Asish Atmaram; Sivakumar, S.; Mohan, D.
This study was aimed to understand the current status, distribution pattern, habitat characteristics, nesting success and nesting behaviour of Oriental Whitebacked vulture in the Konkan coast during a breeding season between December 2010 and May 2011. A total of 24 sites either nesting or feeding were located all along the Konkan coasts of Maharashtra during the survey using area search method as well as interview based techniques. Study shows that there was no significant difference in the habitats of both active and inactive nesting sites in the Konkan coast which indicates that the decline of nesting population of vulatures in the region may not be exclusively due to habitat destruction
Behavioural Ecology of Colony Formation and Function of Colonial Breeding in Chtnut-Headed Bee-Eater.
(Wildlife Institute of India, Dehradun, 2011) Supriya; Vasudevan, K.; Mohan, D.
Breeding in densely distributed territories that contain no other resources apart from breeding site is known as colonial breeding. Despite several long-term investigations, there are several questions regarding colony formation, the function of coloniality and the variation in colony sizes that remain unanswered. Chestnut-headed bee-eaters (Merops leschenaulti) are tropical Old World birds (Family Meropidae) that breed both solitarily and in small colonies. Hence they are well-suited subjects for the study of colonial breeding. This study was conducted for five months from December 2010 to May 2011 in parts of Haliyal division and Karwar division in Uttara Kannada district, Karnataka. It is an attempt to explain the variation in colony size through gaining insights into the behaviour of colony formation and function of colonial breeding. A combination of measuring habitat characteristics, capturing and measuring birds, recording reproductive success of breeding pairs across a gradient of colony sizes and behavioural observations were used. A total of 17 nests were found during the course of the study distributed over three colonies and five solitary nests. No significant difference was found between habitat characteristics at solitary and colony nests. Also, there was no shortage of potential breeding sites, as found by the ratio of number of nests to the amount of substrate available. This suggests that the mechanism of colony formation in CHB is conspecific attraction and is not merely habitat mediated aggregation. The body size of the colony nesters was found to be greater than the body size of solitary nesters. This implies that the optimum colony-size is different for different individuals, with larger individuals having a preference for colony nesting. Program MARK was used to analyze nest survival data. It was found that the daily survival rate of nests was not significantly different across colonies of different sizes, lending further credence to the hypothesis that different individuals have different colony-size optima. Colony nests were initiated about a week before the solitary nests and nesting was more synchronous at colony sites. During the nest digging stage of breeding, a number of aerial chases were observed between the birds, which hint at a role for despotism in influencing variation in colony sizes. Provisioning frequency was found to be higher and showing larger variation at solitary nests than at colony nests. A possible explanation for this is that there is greater competition at colony sites. Therefore, colony-nesting must be having some other benefit that compensates for the cost of competition. Further investigations into the conspecific cue that mediates colony formation and· the benefit of coloniality need to be carried out.
Influence of extractive disturbances on forest bird communities in Shiwalik landscape, India.
(Wildlife Institute of India, Dehradun, 2015) Monica; Rawat, G.S.; Mohan, D.
Frequent extraction of plant biomass in the form of timber, firewood, fodder, and non-timber forest products (NTFP) by rural populations, is the most widespread disturbances in the tropical forests. These disturbances not only alter habitat characteristics but also affect habitat use, survival and fitness of biotic communities. Birds are highly sensitive to modification in their habitat and therefore amongst the best model taxa to examine and monitor impacts of these cryptic disturbances. In order to understand the dynamics of small-scale extractive disturbances and their effects on floral and faunal community, I undertook a study in Shiwalik landscape of northern India. The objectives of research were to: 1. Identify the major causes of disturbance in three main forest type of this landscape and assess if disturbance depends on degree of protection. 2. Quantify impacts of disturbances on different layers of vegetation (tree and shrub) and examine changes in structure and composition of the habitat, if iii any. Executive Summary 3. Investigate the response of birds community and foraging guild levels to habitat degradation in different forest types during breeding and non-breeding seasons. 4. Identify indicator bird species suitable for future monitoring of small-scale extractive disturbances in this landscape. A contiguous stretch of the Shiwalik landscape between river Yamuna in the west and river Ganga in the east was selected to carry out this study.
Responses Shown by Bird Communities to Teak Palatations in Sagar Forest Division, Karnataka
(Wildlife Institute of India, Dehradun, 2009) Barve, Sahas S.; Mohan, D.; Qureshi, Qamar
This study was aimed at discerning the responses shown by bird communities to teak plantations of various age classes in Sagar Forest Division, Karnataka within Latitude 13° 36' and 14° 38' North 74° Longitude 38' and 75° 32'East Latitude. Birds were sampled using line transects in three habitat strata, natural plantations, mature teak plantations and young teak plantations. Density, diversity and community similarity were the chief ecological responses that were quantified to bring out differences in the usage of forest plantations by native bird fauna. Habitat (vegetation) correlates, both structural and floristic were quantified to establish the reasons for differences. The sampling period was from December 2008 to April 2009. This period was divided into two seasons, winter and summer. A total of 9 transects were laid, marked and sampled at least 4 times per season. Birds were divided into three feeding guilds and three habitat guilds for analysis. The overall density of birds across the three strata was found to be higher in summer than in winter. However a guild level analysis showed that in winter while insectivorous birds were most abundant in natural forest with decreasing density towards young plantations (F (6.241) , p< 0.05). There was no difference in their density in summer. Phytophagous birds showed the exact reverse trend. Density of this guild was higher in young plantations than natural forests and mature plantations in winter and summer (F(S.689), p< 0.05), (F (14.302), p< 0.01) respectively. Overall diversity of birds showed a trend of decreasing species richness from natural forests to young plantations in both seasons. However this difference was almost non existent in summer at the guild level. The abundance of birds belonging to evergreen and moist deciduous forests shows a consistent· rise in abundance from winter to summer in all the three strata. There is also evidence that there is ingression of individuals of species that were common to both seasons possibly for nesting. The overall community similarity is quite high between the three strata and it increases from winter to summer. Bird diversity was found to be affected by the vertical spread of vegetation and tree height heterogeneity (R=0.871, p
Species interactions with in mixed species bird flocks along an Elevational gradient in the Western Himalaya.
(Wildlife Institute of India, Dehradun, 2021) Gokhale, Pranav; Kumar, R.S.; Mohan, D.
Mixed-species bird flocks (hereafter, “flocks”) are an interactive community of largely insectivorous birds, which move and forage together to gain enhanced access to resources and protection from predation. In this study, I aimed to investigate a question: do interspecific interactions within mixed-species flocks change along an elevational gradient? To test this, I carried out this study in the Garhwal region of the Western Himalaya in Dehradun District, Uttarakhand from January to April 2021 (spanned across two seasons). The study areas comprised of three field sites along an elevation gradient from western part of the Rajaji Tiger Reserve (300 m ASL) to Mussoorie (2200 m ASL). I sampled flocks and relative abundances of birds on the two pre-existing trails in each of the three field sites. I walked each trail 10 to 13 times. I recorded species identity, group/cluster size of all birds seen inside as well as outside flocks on the trail and within 10 m on either side of the trail. I assessed arthropod prey availability in winter for the flocking species by using branch bagging technique on the same trails. In total, I clipped 150 branches for the three elevations. I calculated species-specific flocking propensity for each elevation from the information on birds seen within and outside flocks. I used network density (potentially realised associations) and weighted degree (associated strength) to quantify the interspecific interactions (associations) within flocks. To control for the influence of species availability on flock network properties, I generated null flocks using an abundance-based null model. I recorded 80 flocking species in 412 flocks, of which, 179 flocks were observed at the High elevation, 156 at the Mid elevation and 77 at the Low elevation. Majority of species in the Western Himalayan flocks were insectivorous gleaner. I found insect prey availability (resource) to decrease with increasing elevation in winter. As expected, flocking propensity, network density and weighted degree increased with elevation in both seasons indicating greater potentially realised associations and high strength of associations between species. Interestingly, the Low elevation flocks disintegrated completely at the onset of summer possibly due to the greater availability of resources, or an upward migration of species for breeding. I did not analyse the Low elevation flocks in summer due to small sample size (n=5). Flocking propensity and network density decreased from winter to summer at Mid and High elevation while, weighted degrees decreased only for the Mid elevation. This is likely that true summer may not have started at the High elevation during the course of my fieldwork. To conclude, with increasing elevation in both seasons, species not just flocked more, but associated with many species and these associations became stronger, potentially due to the scarcity of resources. It is possible that species may not be able to access resources efficiently when foraging on their own at the High elevation, compelling them to participate in flocks to avail complementary benefits from many other species.
Study of Some Important Aspects of Breeding Ecology and Vocalization of Jungle Prinia in Siswan Community Reserve Punjab India
(Wildlife Institute of India, Dehradun, 2021) Chandra, Vignesh M.; Mohan, D.; Singh, Pratap
Several groups of songbirds including North-American wood warblers belonging to the genus Vermivora, Parula, Dendroica, and Setophaga have developed two singing modes or categories of songs which are having different functions. Among Indian breeding birds Jungle Prinia along with three Phylloscopus warblers (humei, pulcher, and chloronotus) are known to have two singing modes. To find out function of two singing modes by the bird during different stages of breeding in Jungle Prinia, I studied the use of two singing modes of Jungle Prinia and its relation with its habitat or vegetation. My study suggests that the singing mode A is related to aggressive mal-male interactions and singing mode B is linger distance signal and has role in male and female interactions. Bird density was found to be positively related to the differential singing mode B use.
Winter Ecology of Three Species of Phylloscopus Warblers
(Wildlife Institute of India, Dehradun, 2007) Ghosh, Mousumi; Singh, Pratap; Mohan, D.
This study focused on three species of Phylloscopus warblers, P. humei, P. xanthoschistos, and P. chloronofus which overwinter sympatrically in the foothills of western Himalayas. The patterns of habitat occupancy, foraging behaviour, and foraging microhabitat of three species of warblers were examined to determine the nature of ecological complementarity facilitating their co-existence in the non-breeding season. Moreover, investigating the morphology-ecology associations among congeners also becomes critical since recent divergence may hinder our understanding of the mechanisms of their ecological segregation, as is the case with these species. Hence, morphology-ecology associations were also examined. A total of 91 points were sampled for bird detections five times each between December 2006 and March 2007. Prey abundances across habitat types were quantified. Behavioural data was also collected. The three species were found to differ in the occupancy of the sampled area. However, the bird occupancy did not correlate with differences in prey abundances across habitat types. The warbler species showed clear segregation in the use of foraging behaviour, foraging microhabitat, and proportion of large prey intake. The movement pattern was also found to vary across the three species. Morphology-ecology associations revealed the close interaction of morphology and ecology in shaping the ecological segregation of the three species in the non-breeding season. One major finding was that P. xanthoschistos is able to meet its demand for large arthropods in this northern site (31.5 % large prey intake) previously believed to be low in large arthropod abundance. Finally, the study demonstrated that the ecology of P. xanthoschistos (previously Seicercus) is very similar to other members of the genus Phylloscopus.