STATE OF CONSERVATION AND POPULATION STRUCTURE OF BIRD SPECIES INHABITING IN VARIOUS SUBTROPICAL URBAN FORESTS

: To determine the conservation status and population structure of avian species living in various subtropical broadleaved urban forests, namely Dob Ghar, Kamal Khan, Kityari, Palamar, Seya Sar and Shahabad of Pakistan, we aimed to use the distance sampling line transect process. To avoid double counting of the same bird individual, a total of 180 counting points were set at 250 m from each other. In all, between December 2017 and November 2018, 2,879 individuals representing 53 species, 28 families and 9 orders were detected. One species was vulnerable (VU) out of 53 bird species, while the remaining 52 species were the least concerned (LC). In particular, the results of the distance analysis indicate that, in six subtropical broad-leaved forests, the bird population can vary. For eg, Palamar (0.954 ± 0.221 birds/ha) and Kityari (0.938 ± 0.162 birds/ha) were densely populated by bird species, while Kamal Khan (0.102 ± 0.178 birds/ha) was less concerm. Similarly, the CAP findings showed that bird species in Dob Ghar were more diverse (H’ = 33.92 ± 1.368) and equally distributed (E = 0.9657 ± 0.004) and that the Shahabad ecosystem was rich in bird species (R 1 = 8.007 ± 0.053) compared to other habitats. In addition, the length of the twigs and topological changes in the dendrogram have shown that bird diversity may vary from habitat to habitat. The bird species were classified into eight foraging guilds. Insectivores were the most abundant bird species using all habitats in abundance. By cons, Carnivore/Piscivore/Insectivore averted to use the forest habitats Dob Ghar and Frugivore Kamal Khan and Dob Ghar. The findings of this study revealed that broad-leaved subtropical urban forests are home to a wide range of avian species. However, habitat selection among bird species varied across habitats according to vegetation structure and composition, food resources, adjoining habitats, and human settlements.


Figure 1: Location map of the study area
Bird Survey: Distance sampling line transect is the robust and is the robust, adequate and most efficient method to identify avian populations in different habitats (Buckland et al., 2001;Cassey et al., 2007;Green et al., 2010) to analyze density in heterogenous habitats, i.e. to sample bird density in environmental gradients (Broekema and Overdyck, 2012). This technique enabled the perpendicular distance between the bird and the observer to be determined by means of a visual approximation (Figure 2). DISTANCE computes x values which can be used to measure population density (Buckland et al., 2004). Bird detection accuracy and reliability depend on environmental conditions, species activity and observer skills (Diefenbach et al., 2003;Marques et al., 2007;Innes et al., 2012). The problem of variable detection is solved by distance sampling and accurate density estimates are given (Buckland, 2006). A total of 120 transect lines were randomized over a hilly topography (20 transect lines in each habitat with a length of 2 km) to assess bird occupancy in each habitat. Birds were detected early in the morning from 7:30 a.m. to 11:00 a.m. December 2017 from November 2018. All the birds seen and heard were reported in each survey. By visual evaluation, the perpendicular distance between the birds and the transect line was reported. Opportunistic observations of airborne birds of unknown origin were also reported, but were not included in the study. Buckland et al. (2004), Gregory et al. (2006), Aborn (2007) and Nadeau et al. were the basis for the sampling method (2008).

DATA ANALYSIS
Relative Abundance: The relative abundance (%) of bird species was alculated using the expression: n/N x 100 (Where, n is the number of a particular bird species and N is the total number of all species).
Bird density: For future conservation and management planning and to check the current status of bird species in a given habitat, the determination of the exact population size is very important. Bird density was calculated by the Buckland et al. software DISTANCE (version 6.1) (2004). The key to distance sampling is to use the distribution of observed distances to determine the "sensing function", g (y), the probability of estimating a bird from a distance y. This function can then be used to measure the mean probability of detection of a bird given that it is inside w of the point, Pa. Provided a Pa estimate, the density of birds can be calculated as: Where, a is the size of the covered region, n is the number of birds seen, and Pˆ a (zi) is the estimated probability of detecting the ith bird given that it is within w of the line and has the covariate values zi (Marsden, 1999;Buckland et al., 2001). Based on the reduced sample size, the densities of birds of these species with fewer than 10 detections were not determined. The approach as outlined by Marsden has been followed (1999).

Bird Diversity Indices:
Monitoring the diversity of existing bird species is an important step in the description of the structures of bird communities and the identification of appropriate habitats. Diversity indices, such as species diversity, species richness and regularity, were identified using the Community Analysis Kit by Henderson and Seaby (2007). (CAP,version 4.0). In this study, the Shannon Diversity Index, Margalef Richness Index and McIntosh Regularity Index were used to determine avian species diversity indices in six broad-leaved forest habitats.

Species Diversity:
Diversity is an index that takes into account the number of birds in a given ecosystem and the relative abundance and offers more details on the nature of the population, such as scarcity and avian species dominance. For example; Shannon's Diversity Index: Where, H' designates diversity, S indicates the number of species, i specifies the abundance of species, N relates to the total number of all individuals and pi is the relative abundance of each species.

Species Richness:
Species richness is the number of different bird species that occur in residential habitat. It also provides data on the homogeneity and scarcity of the structure of the avian population. For example; Margalef's Richness Index: (R) = S-1/ln (n) Where, S = Σ species in the plot and n =Σ Individuals of all species.
Species Evenness: Uniformity is the relative abundance of individual avian species in a specific habitat.. For example; McIntosh's Index: Where, N is the total number of individuals in the sample and U is given by the expression: Where, n (i) is the number of individuals in the ith species and the summation is undertaken over all the species, U is the Euclidean distance of the community from the origin.

Comparison of Bird Diversity Indices in Six Subtropical Broadleaved Urban Forest Habitats:
A Kruskal-Wallis one-way analysis of variance (ANOVA) and a Tukey's (HSD) test (Analytical Software, version 8.1) were used to investigate the significance of differences in diversity indices among six subtropical broadleaved forest habitats (McGraw-Hill, 2008). McGraw-Hill

Comparison of Foraging Guild Structure in Six Subtropical Broadleaved Urban Forest Habitats:
The structure of the feeding guild is an assemblage of bird species that consume the same food resources using different techniques. Bird species were ranked in eight guilds based on dietary behaviour, food selection and habitat preferences. The method used as described by Nebel et al. (2005); Leso and Kropil, (2007); Burger et al. (2007) and Pinotti et al. (2012).

Bird Species Composition and Relative Abundance:
In total, 2879 individuals representing 53 species from 28 families and 9 orders detected in six subtropical urban broadleaved forest habitats, i.e. Shahabad (51 species; 515 birds), Seya Sar (47 species; 437individuals), Palamar (46 species; 445 detections), Kamal Khan (50 species; 497 individuals), Dob Ghar (45 species; 391 individuals) and Kityari (49 species; 594 individuals). Out of 53 bird species, one species was vulnerable (VU) while 52 other species were least of concern (SC) according to the IUCN Red List. Relative abundance of avian species may vary from habitat to habitat. For example; common myna (35, 32, 21 detections) in Shahabad, Kamal Khan and Dob Ghar; scarlet rosefinch (35 detections) in Seya Sar; chakor (35 detections) in Palamar; and house crow (80 detections) in Kityari were the most dominant bird species within six forest habitats. In contrast, shikra and speckeled wood pigeon (Shahabad), shikra, yellow-footed green pigeon, and Indian roller (Seya Sar); blue whistling thrush, white-throated kingfisher and green bee-eater (Palamar); shikra, Indian roller and Asian koel (Kamal Khan); shikra (Dob Ghar); and shikra and black-shouldered kite (Kityari) were the rarest bird species, i.e., each recorded only once (Table 1). The abundance ranking curve showed the distribution patterns of relative abundance of birds in six subtropical deciduous persistent forests. The abundance classification curve provides information on abundance, proportionate abundance, logarithmic abundance, and accumulated proportionate abundance. The abundance curve is a 2D graphic with relative abundance on the Y axis and abundance rank on the X axis. The graph indicates that the relative abundance of birds in six habitats can vary between habitats. The curve shows the distribution of bird species, i.e. the steep slope shows low regularity because high-ranking species show higher abundance than low-ranking species. In addition, the shallow gradient has the highest consistence ( Figure 3).

Comparison of Bird Density in Six Subtropical Broadleaved Urban Forest Habitats:
The findings showed that the more active habitats supporting the higher bird population were Palamar (0.954 ± 0.221 birds/ha) and Kityari (0.938 ± 0.162 birds/ha). In comparison, Kamal Khan's broad-leafed subtropical habitat (0.102 ± 0.178 birds/ha) was less productive and favoured by avian species (Table 2).

Bird Density in Dob Ghar Subtropical Broadleaved Urban Forest:
The results revealed that Black-throated thrush (0.966 ± 0.329 / ha), Indian paradise flycatcher (0.896 ± 0.326 / ha ) and common rosefinch (0.833 ± 0.259 / ha) were the three most populated bird species that preferred to utilize the Dob Ghar subtropical broadleaved urban forest. However, the density of 23 bird species was not processed due to the small sample size i.e. less than 10 individual detections (Table 3).

Bird Density in Seya Sar Subtropical Broadleaved Urban Forest:
The findings indicated that cinereous tit (0.926 ± 0.324 / ha) and Eurasian tree sparrow (0.716 ± 0.268 / ha) were the most dominant bird species that densely occupied the Seya Sar subtropical evergreen broadleaved urban forest. Furthermore, the density of 28 bird species was not examined due to the small sample size (Table 3).

Bird Density in Kamal Khan Subtropical Broadleaved Urban Forest:
The findings of this study indicated that house sparrow and common babbler were the most dominant bird species that had the highest bird density (0.961 ± 0.307 / ha and 0.887 ± 0.249 / ha) in Kamal Khan subtropical broadleaved forest habitat. In contrast, the density of 30 bird species was not analyzed due to the small sample size (Table 3).

Bird Density in Palamar Subtropical Broadleaved Urban Forest:
The results of Distance analysis showed that common myna (0.868 ± 0.284 / ha), common babbler (0.790 ± 0.253 / ha), cinereous tit (0.757 ± 0.235 / ha), and black-throated thrush (0.732 ± 0.281 / ha) were the four most abundant bird species having the highest bird density in Palamar subtropical broadleaved urban forest habitat. On the contrary, the density of 26 bird species was not analyzed due to small sample size (Table 3).

Comparison of Bird Diversity Indices in Six Subtropical Broadleaved Urban Forest Habitats: Community Analysis
Package test illustrated that bird diversity in six subtropical broadleaved urban forests varied i.e. the Dob Ghar (H' = 33.92 ± 1.368) habitat was more diverse in avian species composition and Kityari (H' = 20.78 ± 1.368) was the least diverse as compared to other habitats. In addition, Pooled Rarefaction and Diversity Ordering -Renyi test was also run to compare the relative diversity and richness differences among six habitats (Figure 4 and 5). Notably, the highest avian richness was determined in Shahabad (R1 = 8.007 ± 0.053) and the least richness found in Dob Ghar (R1 = 7.372 ± 0.053). Likewise, the avian species were evenly distributed in Dob Ghar (E = 0.9657 ± 0.004) and sparsely in Kityari (E = 0.9065 ± 0.004) respectively (Table 4 and Figure 6).

Comparison of Bird Diversity Indices in Six Subtropical Broadleaved Urban Forest Habitats:
Kruskal-Wallis One-Way ANOVA and Tukey's HSD indicated that the bird diversity indices in six subtropical broadleaved urban forest habitats were significantly different (F5, 17 = 61.7, p< 0.05).

Comparison of Foraging Guilds of Avian Species in Six Subtropical Broadleaved Urban Forest Habitats:
The results of foraging guilds revealed that foraging guilds of avian species may vary from habitat to hbitat. Insectivore were the most abundant bird species (Greenish warbler, Lemon-rumped warbler, Common chiffchaff, Cinereous tit, Oriental magpie robin, Pied bushchat, Grey wagtail, White wagtail, Indian paradise flycatcher, Common babbler, Bay-backed shrike, Grey-backed shrike, Common swallow, Rock bunting, Black drongo, Crested lark, Green Beeeater, and Indian roller) that heavily utilized all habitats. Likewise, Omnivore (5.592%) heavily occupied the Kityari urban forest habitat. In contrast, Carnivore/Piscivore/Insectivore (White-throated kingfisher) avoided to use Dob Ghar and Furgivore (Speckled wood pigeon and Yellow-footed green pigeon) also avoided to visit Kamal Khan and Dob Ghar urban forest habitats (Table 5).

DISCUSSION
A comprehensive evaluation of avian diversity demonstrates the habitat-level ecosystem health that is paramount in conservation activities (Stem et al., 2005) since it exposes the details that explain the driving forces that affect population variability directly or indirectly. The birds are bio-indicators of habitat health and productivity (Gregory and Strien, 2010;Goteli and Chao, 2013). The detailed knowledge on the parameters of the bird population helps to explain the key driving factors that play an important role in the home range, the selection of habitats and the effect of human interference on avian diversity and habitat alteration (Raman, 2006;Buxton et al., 2018).
Determining the conservation status and population structure of avian species living in various broadleaved subtropical urban forests has provide a solid foundation for better understanding of ecological trends and processes. The results of this study indicated that by providing a wide variety of food resources and niches and harsh environments, avian diversity will increase with heterogeneous habitats. Less vegetated habitats, by comparison, were favoured only by some animals. With landscape diversity, species abundance increases and decreases with less coverage of vegetation due to the lack of food resources (Koadmon et al., 2007;Bar-Massada and Wood, 2014;Lee and Martin, 2017).
The conservation status and population structure of avian species living in various subtropical broad-leaved urban forests provided information on the scarcity and abundance that will assist in future conservation and management planning. The most active, diverse, and complex ecosystems that covered about 30-40 percent of Pakistan's forested area were subtropical broadleaved urban forests. However, these urban forests are of vital significance for the protection of both wildlife and human beings (Waring and Running, 2007;WBD, 2018). These urban forests, sadly, are deforested, degraded, isolated and converted into agricultural fields, human settlements that have decreased bird populations negatively..
In particular, records of 53 bird species have shown that urban forests are of critical importance for avian species. The results of the Distance Analysis and CAP test suggested that the indices of bird density and diversity can differ across six subtropical broad-leaved urban forests. This indicates that the range of habitats among bird species which vary depending on the composition of the vegetation, the availability of food resources (e.g. insects, fruits, grains, amphibians, reptiles and small mammals), adjacent habitats, i.e. agricultural fields and orchards offering acceptable forage and breeding sites, and human intervention. The other explanation may be that these bird species belong to various foraging guilds, i.e., in heterogeneous environments, they forage and eat a range of food resources. Thrushes, for instance, frequently prefer dense scrub vegetation stands, forest edges, wet ditches and grassy areas to feed on invertebrates such as caterpillars, ants, wasps, grasshoppers, beetles and wing flies.
Furthermore, they also hunt for invertebrates such as centipedes and millipedes in leaf litter. For invertebrates, i.e. larvae, caterpillars, worms, and ants, Babblers pick relatively open woodlands, scrub plants, forest remains, and forest edges to forage. Thickets, woodlands, forest edges near riparian regions and orchards for seeds, buds, shoots, fruits and orchards for foraging are often favored by finches. Pigeons rely on a variety of fruits on fruiting trees to forage. As grassy areas are rich in grains and insects, Francolins and Chakor prefer barren hills dominated by grasses and sparse shrub vegetation and also provide hiding cover from predators and ideal breeding sites. In addition, they also hunt for invertebrates in leaf litter, such as centipedes and millipedes. Relatively open woodlands, scrub plants, forest remains, and forest edges are picked by babblers to forage. For seeds, buds, shoots, berries, and fruit forage, finches often choose thickets, woodlands, forest edges near riparian areas, and orchards.
A record of five species of raptors, namely, shikra, besra, kites, kestrels and owls, showed that these subtropical broadleaved urban forests are an attractive habitat for passerine birds, reptiles (lizards and snakes), small mammals (shrews, rats, squirrels, and mice). The other explanation may be that in these urban forests, these birds are hunting in nearby habitats and eating their prey. Similarly, in higher numbers, insectivore birds such as minivets, woodpeckers, bee-eaters, flycatchers, wagtails, robins, bushchats, warblers, shrikes, and tree-creepers were reported. The diversity of insect-eating birds may be due to the richness and diversity of insects, such as flies, moths, beetles, grasshoppers, caterpillars, wasps, ants, and termites, which are their staple diet. This may be due to the presence of trees, shrubs, and grasses that also bear flowers and fruits that are fruiting and flowering. Similarly, adequate numbers of game birds, i.e. francolin, chakor, quails, and doves were also found. These birds have also chosen grasses and open landscapes to feed on seeds, grass grains, crops for agriculture and cereals.
In addition, frugivore/insectivore birds were also detected in good numbers, such as starlings, orioles, thrushes and bulbuls. The phenomenon of a large number of birds eating fruit and insects may be attributed to the presence of a variety of fruits and insect diversity. The other explanation may be that agricultural fields and orchards have surrounded these forests, sometimes bearing flowers and juicy fruits that attract a wide variety of insect species to make use of these adjacent habitats. This shows that birds are habitat specialists, choose suitable environments, rich food supplies, ideal forage and breeding sites, and shelter for them (Whelan, 2001;Robertson et al., 2013;Cloyed, 2014;Mansor et al., 2015;Styring and Sheldon, 2016).

CONCLUSIONS
Overall, the findings of this study show that subtropical wide-leaved urban forests are active, abundant, and complex habitats that have attracted a broad variety of avian species from higher bird populations to use them. It is therefore strongly suggested that these urban forests should be designated as reserved forests in order to increase the population of highly endangered and threatened avian species.