Wildbuzz: Beyond the monsoon’s pale
A Sarus crane may not wither away like a pining graveside flower when the mate dies. The surviving bird turns its back to the dead and flies around with eyes kept peeled for a new lover!Updated: Jun 30, 2018 22:15 IST
Culture’s venerated symbols of marital fidelity, Sarus cranes, do not always live up to the romantic expectation: ‘only death dare do us part’. Scientific data collection and careful field observation disproves popular folklore and reveals cases of divorce (separation) in Sarus cranes. A Sarus crane may not wither away like a pining graveside flower when the mate dies. The surviving bird turns its back to the dead and flies around with eyes kept peeled for a new lover! Further, mate change is known in almost all crane species in captivity the world over, some of whom are similarly anointed with the mythology of fidelity.
Testing the truth of a related set of theories, avian scientists recently arrived at the correct reason for unseasonal nesting by these iconic birds. KS Gopi Sundar, Mohammed Yaseen and Kandarp Kathju of the International Crane Foundation (ICF) conducted the largest-scale and longest-term evaluation of any aspect of Sarus crane ecology to date. “The ICF team compiled observations of Sarus nesting between 2004-2017 from Haryana, Gujarat, Rajasthan, and Uttar Pradesh. Over 5,000 individual instances of Sarus breeding were documented,” Sundar, a celebrated and award-winning avian scientist, told this writer.
“Sarus breed during monsoons with few nests initiated outside of the monsoon. Several hypothesis have been put forth to explain unseasonal nesting but a careful evaluation of the hypotheses had been absent,” said the study titled, ‘Role of Artificial Habitats and Rainfall Patterns in Unseasonal Nesting of Sarus cranes in South Asia’. The prevailing, but untested, hypotheses for post-monsoon breeding were (1) two Sarus populations are present, each nesting in a different season; and/or (2) some pairs raise a second brood outside the monsoon to maximise reproductive success.
However, the ICF study disproved the above hypotheses and established that Sarus pairs that could not nest successfully, or lost their chicks, during regular nesting period might have a second nest during the secondary season if conditions are conducive. “Sarus nests outside the monsoon were very rare (0.3% of all nests) and were initiated when Sarus pairs were in areas with artificial water sources (irrigation canals or reservoirs) or faced abnormal monsoonal conditions. Unseasonal nests were initiated only when breeding pairs had been unsuccessful in raising chicks in the previous primary nesting season. Altered cropping patterns associated with increased artificial irrigation and changing rainfall patterns appear responsible for unseasonal nesting in Sarus cranes. Nesting of this species outside the monsoon may increase in response to increasing changes in cropping patterns and changing rainfall conditions,” said Sundar.
Though Sarus cranes are listed as a globally vulnerable species, the ICF study noted with optimism: “ Sarus cranes are getting increased opportunities for breeding, either via man-made structures created for irrigating crops or via unusual rainfall patterns predicted to occur more often.
Man-made structures made to increase farming output and human-induced changing rainfall patterns favouring wild species are rare, but these altered conditions could support increased breeding by Sarus cranes.”