Eco-biology and conservation of potential insectivorous birds in the arable biomes of central Punjab

The present study was conducted to investigate the eco-biology of insect predator avian species and the effects of environmental factors on the eco-biology and bird populations in Punjab, Pakistan. Data on ecology and other aspects of bank myna was collected from three districts of Central Punjab including Faisalabad (an industrial area with large effects of heavy metals by usage of sewage water of industries in irrigation & pesticides), Sargodha (with medium level of industries & pesticides use) and Mandi Bahauddin (no industry and low use of pesticide). Specimens were collected to observe gut contents. Gut contents were analyzed to account for the prey and feeding niche. Major insect pests of crops were identified and listed from gut contents. Relative population density of useful birds was assessed and continuously monitored for population trends around the year. Breeding ecology of both predacious birds was studied to evaluate breeding success, mortality rate and to weigh up the effects of pesticides used and pollution. Breeding ecology, population dynamics and gut contents analysis were significantly (P ≤ 0.001; R ≥ 0.75) influenced by the use of pesticides. It was concluded that use of pesticides without studying their toxic effects is detrimental to these predacious birds. Blind sprays should be prohibited and alternatives should be adopted to conserve the predacious birds in order to achieve effective biological control.


Introduction
The bank myna (Acridotheres ginginianus) is a member of family Sturnidae, native to South Asia, smaller in size but similar in colour to the common mynah (A.tristis) the major differences are: the presence of a brick red bare skin patch behind the eye in place of yellow; greyer undersides with presence of slight tuft of feathers, bearing a resemblance with the jungle myna (A.fuscus).Head is black on the crown and sides and the upper plumage is slaty grey while the underside is lighter grey with pale pink plumage towards the center of the abdomen the birds have black wings with a wing patch at the base of the primaries, and the tips of the outer tail feathers are pale pinkish buff.The sexes are indistinguishable in the field.Young birds have a browner head and neck [1].Bank mynas feed on grains, insects and fruits.They feed on a variety of insects, including some crop pests such as Achaea janata whose caterpillars feed on castor [2].Clutch size normally ranges from 4-6 eggs and average size of egg measured 30.8×21.99 mm.Incubation period ranges from 17-18 days and fledging period from 22-24 days [3].Bank mynas build nests in cavities of trees, walls and canal bank and breed from sea-level to 3000 m in the Himalayas.Nesting material usually consists of twigs, roots, tow and rubbish.Sometime they also use nests of woodpeckers, parakeets, etc. and aggressive behaviour is used to contribute towards its success as an invasive species [4].Food choice of birds can be assessed by analyzing gut contents.Population structure and gut contents of 32 bird species were analyzed by [5].Among them 31 species were Passeriformes and one Coraciiform.Whereas 23 were endemic and 9 were migratory in nature.Indian wren warbler, bank myna and jungle babbler, were recorded frequently Rosy Pastor, Jungle Sparrow, Yellow-throated Sparrows were rare; small Green Bee Eater was recorded during maturity stage of cotton with density of 0.8 birds/hectare and potential in insect predation.Indian wren warbler, jungle babbler, common babbler and bank myna, were recorded throughout the year and their combined population was estimated up to 7.1 birds/ha.The total estimated bird density was 14.6 birds per hectare.More than ⅓ (37%) of the bird species mostly concentrate on insects for food.Insects belonging to the orders Hymenoptera and Hemiptera formed the major proportion of arthropod based food.Common aphids and thrips dominated the food of the Indian Wren Warbler.Cattle movements disturb insect population in fields.However, [6] investigated ecological linkages of the bird species with livestock.The insects in the pastureland dislodged by the livestock are eaten by cattle egrets, bank mynas and black drongos.Bank mynas and black drongos were estimated to consume insect mass of consuming upto 1 /6 of their body weight per day; however, Cattle Egrets and Crested Larks were recorded consuming upto ⅓ of their own body weight per day.The percentage of grasshoppers and beetles in diets of these species was found higher than found in guts of other insectivorous bird species.Ticks are also found in gut contents.[7] observed crops (n=7,334) contents from 239 species of birds for ticks.They recorded ticks in bank myna, helmeted guinea fowl, crowned plover and lila breasted roller.All these ticks belonged to genera Boophilus, Hyalomma and Rhipicephalus.Gut content of birds' species reported showed diversity of insect species preyed by birds.Some birds prefer certain insects while others reject them.It implies that birds are prey specific to some extent.Clutch size normally ranged from 4-6 eggs and average size of egg measured 30.8×21.99mm.Incubation period ranged from 17-18days and fledging period from 22-24 days [8].Some time they also use nests of woodpeckers, parakeets etc. and aggressive behavior is recorded for success towards invasive species [4]

Materials and methods
The present experiment was conducted at three locations of Punjab (Faisalabad, Sargodha and Mandi Bahauddin).Two sites were selected in each district with GPS readings to identify the actual location of selected study site.Faisalabad 30 o 40´to 31 o 47´N, 72 o 42´ to 73 o 40´E, Sargodha 31° 49' 60N, 72° 37' 60E and Mandi Bahauddin 32° 34' 60N, 73° 30' 0E.Population surveys of the selected birds from three habitats (six sites) were made to record the distribution of bird species among these sites.Survey was conducted using three method: i) By direct visual analysis, ii) by telescope studies iii) by taking pictures and counting birds.Among these sites, there was an extremely large range of population sizes among bird species, (<1000 mature individuals) and these fluctuated with regard to the nature of habitat extent/ quality.In some places population size was recorded in small number at 2-3 locations/ fragmentation [10].Population was estimated by transect methods through searching and counting active nests of the cattle egret and bank myna in the aforesaid areas, either on foot, by boat or vehicle.Active nests were identified by seeing the pairs engaged in nest building and/or renovation.Gut content analysis was made to determine the detrimental effects of pesticides and pollution.10 birds were hunted/shot each time and 24 observations were completed during the study by two weeks sampling (n=240), The birds were killed using an air gun/shot gun (Diana 35 Model BB shots) according to a specific schedule at 10-1l am and 4-5 pm.The crop of each killed bird was extracted in the field, tagged properly, brought to the lab and was preserved in 10% alcohol for final analyses (Pedigo, 1996), the morphological measurements made from the hunted birds.At the end of each trip the crops were cut opened; contents were weighed and taken out in a shallow pans or petri-dishes.Needles were used to spread the items for identification.Fragments of the insects were isolated to identify the species and the total number of useful and harmful arthropods consumed.Field lens (10X) and microscope was also used occasionally to confirm the identification of insects.Observations were recorded continuously throughout the research period according to the previously described schedule

Morpho-taxonomical features
During present study10 birds of bank myna were killed and 15 live birds were visualized by telescope in each survey to study the morphological features (Table 1) from each study site at the end of sampling season (October and March), and following observations were recorded: it was difficult to differentiate between sexes in the field and juveniles were with a browner head and neck; head of each birds was black on the crown and sides, whereas upper plumage was slaty grey and underside was lighter grey with pale pink plumage towards the center of the abdomen.Wings were black, having a wing patch at the base of the primaries and the tips of the outer tail feathers were pale pinkish buff.However, naked skin behind the eye was brick red, legs were yellow, and iris was deep red.The study was confirmed by other scientist as the results were in the same pattern [12].

Comparison of feeding flocks of bank myna
The differences between locations were significant (P<0.05) for feeding flock sizes (Table 4).Data on sampling feeding flocks of bank myna from three districts is presented in Table 5 [1, 11].After collection, data were analyzed statistically using Analysis of Variance or Chi square tests.The statistical packages Statistix version 8.1 and SPSS version 16.0 were used for all analysis.

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Cattle Egrets spend their life in colonies.Breeding season varies within Asia.Nesting usually begins with onset of monsoons [8].Breeding success is related to number of newly hatched birds.[9] evaluated the breeding success of Bubulcus ibis (Ardeidae), Egretta thula, Nycticorax nycticorax, Phimosus infuscatus and Plegadis chihi for two consecutive nesting seasons.Mean clutch size for B. ibis was 2.59 and 2.49, respectively.The mean number of nestlings/nest was 1.85 for B. ibis.In both nesting seasons all the species had major success, laying three eggs and raising two nestlings, except for B. ibis.However, breeding success for B. ibis ranged from 1.16 in the first period to 0.99 in the second.