Super Ovulation! The 2000 Breeding Season of
Sarus CraneS (Grus antigone) in Etawah and Mainpuri, India
- K.S. Gopi Sundar, Senior Research Fellow

Abstract

Breeding biology of the Sarus Crane (Grus antigone) was studied in Etawah and Mainpuri districts of Uttar Pradesh. Though conversion of natural wetlands to crop fields and other habitats has been widely regarded as being chiefly responsible in decline of the quality of habitat for the Sarus, no field studies have been forthcoming to show if and how crop fields are sub-optimal habitats. Breeding biology of the Sarus was studied in Etawah and Mainpuri with the purpose of determining differences in productivity of pairs living in natural wetlands as opposed to those in crop fields, in addition to providing descriptors to various aspects of breeding biology in the species in an unprotected, largely agricultural landscape. Based on the composition of territories, breeding pairs were classified as "wetland pairs", (territories with >50% natural wetlands), and "crop-field pairs" (territories with <50% natural wetlands).

A road transect of c. 250 km was used in Etawah and Mainpuri, between June-December 2000 to locate nesting in previously identified territorial, breeding pairs. All nests found were monitored to obtain information on hatching, nesting and breeding success. A total of 65 nests were found, and in addition, 31 families were discovered with pre-fledged young. All families were monitored until the young weaned from their natal territories. Chi-square tests and t-tests have used to analyze data.

Nest initiations were between 27 July to 11 October, with most nests initiated between 11 August–10 September. Mean clutch size was 1.71 with 71% of the nests having two eggs each. While no wetland pair nested in crop-fields, 13 crop-field pairs nested in wetlands, implying choice of wetlands for nesting sites (c2=19.44, d.f.=1, p<0.001). Mean clutch size was slightly greater in crop-field nests, though not statistically significant (n=56, 1.71 vs. 1.68; p>0.1). Egg sizes (length and volume) were significantly higher for wetland pairs (Students t-test; p<0.05, p<0.001 respectively). Territory size of crop field pairs were significantly greater than those of wetland pairs (Mean territory size (ha) = 32.7 vs. 16.4; c2=5.4, p<0.05).

Overall hatching, fledging and weaning success was low, with human-related factors contributing most to mortality at all stages. Most chick deaths (96%) occurred before the young reached three months of age. A total of 80 young birds weaned from the 96 pairs monitored. Mean number of young hatching, fledging and weaning per breeding pair were higher for wetland pairs though not statistically significant.

The Sarus Crane population in the study area is clearly a growing one. In spite of high mortality at the egg and pre-fledging stage, a large number of young weaned. Wetlands were seen to be beneficial for breeding and crops are clearly sub-optimal. Any attempt at alternation or full-scale conversion of wetlands to crop fields will results in increase of sub-optimal conditions to Sarus Crane.

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