European Journal of Environmental Ecology

TEMPERATURE HUMIDITY INDEX VIS-À-VIS BLACK KITE (Milvus migrans) POPULATION AND MIGRATION PATTERN IN ARID TRACTS IN INDIA

A.K. Kataria* , N.Kataria, R.N. Kumawat and A.K.Gahlot

akkataria1@rediffmail.com

Bikaner, Black kite, population, temperature-humidity index, weather.

The purpose of this investigation was to appraise the migration drift of black kite (Milvus migrans) at Jorbeer Conservation Reserve, Bikaner, Rajasthan (India) over the period from April 2015 to July 2016. The birds’ population was recorded along with environmental temperature and humidity on 1st and15th day of every month. A maximum of 1100 black kites were evidenced in the mid of January 2016 followed by a gradual decline. Minimum number was observed around mid April to beginning of May 2016. Population of black kite was less than 20% in the months from April to September, 2015 and April to July, 2016. April, May and June months of both the years showed extremely high environmental temperatures. From April 2015 to September 2015, THI values swung between 75.5 and 82 with population per cent of below 20%. In October 2015, THI varied from 78.2 to 79 and population per cent varied between 45 and 55%. November to February illustrated THI values as 72 and lower with bird population per cent fluctuating between 63 and 100%. Period from March 2016 to July 2016 showed a marked rise in THI values with concomitant decrement in bird population. Residential population in summer months was lower in year 2016 in comparison to that in 2015 because of comparatively higher THI in year 2016. From October 2015 to March 2016, the presence of birds was above 45%. During December 2015 and January 2016, the bird population was above 80% and October, November and February months showed variation in population between 45 and 78%. It was noted that bird population was affected by environmental temperature and not by humidity. It can be concluded that in the arid area of Rajasthan (Jorbeer Conservation Reserve), black Kite population was higher during extreme cold months when minimum temperature was very low whereas extreme hot environmental temperature period showed minimum concentration of birds. Highest concentration of birds was observed when temperature humidity index (THI) was 72 or low. The upshot of study showed pattern of wintering in this area, however, summer months were not deserted. It can be deduced that migrant species know how to switch on adaptive foraging tactics to visage challenges of food scarcity in both cold and hot periods of year during migration. The investigation will help in understanding how weather influences processes that drive bird population dynamics and in predicting the effects of climate change on threatened ecosystems and bird species.