Seasonal Changes in Total Serum Calcium, Inorganic Phosphate Level and Gonosomatic Index of Bank Myna, Acridotheres ginginianus (Latham) with Reference to Natural Photoperiod

Studies on seasonally breeding wild birds of Indian sub-continent have been grossly neglected in terms of cyclic changes in total serum Ca, Pi and GSI with respect to natural photoperiod. Bank myna is one of the commonest wild seasonal breeder of Northern Indian plains. The bird breeds during April to July. With the advent of summer (in March) and increasing natural photoperiod a marked rise in total serum Ca level of female Bank myna has been recorded. The value reached a peak level of 14.85±0.369 mg/100ml in May, the breeding peak. Male Ca values also recorded a gradual increase corresponding with increasing natural photoperiod and reached a maximum level of 11.26±0.348 mg/100ml in May. Serum Pi values of female birds rose up to 7.65±0.263 mg/100ml and males up to 6.61±0.182 mg/100ml during the breeding period. Both sexes of Bank myna documented gradual increase in GSI along with increasing natural photoperiod. In May, GSI of female was recorded 3.89±0.270 whereas male GSI was 1.98±0.213. High degree of gonadal regression has been observed in birds of both sexes from August to December. Least GSI of 1.24±0.177 in females and 0.724±0.136 in males was recorded in November. Gonadal regression was copuled with reduction in total serum Ca levels. Least Ca value of 7.75±0.235 mg/100ml in females and 7.66±0.202 mg/100ml in males were recorded during November (non-breeding period). Serum Pi values of non-breeding female birds was 6.25±0.133 mg/100ml and that of male bird was 6.20±0.125 mg/100ml. We concluded that natural photoperiod influenced total serum Ca, Pi and GSI of the Bank myna, a seasonally breeding Passerine bird of North Indian plains.