AHMEDABAD: Feeding grounds of sarus crane, a threatened species in India and vulnerable across the world as per International Union for Conservation of Nature (IUCN), are most likely turning into their killing fields, researchers studying the cause for their dwindling have found.
Sarus cranes live close to human habitation and depend on food grains as their primary food source.
However, pesticides used in fields pose a major threat to the birds by either killing them or affecting their calcium metabolism and making the shells of their eggs very fragile, according to researchers of the Salim Ali Centre for Ornithology and Natural History (SACON).
The SACON recently carried out a study ‘Assessment of status, distribution and threats to the population of threatened Sarus Crane Antigone in Gujarat’.
“It was observed that chlorpyrifos (one of the most widely used active ingredients in agricultural insect control products) showed strong relation with eggshell thickness.
However, due to lack of published information on the role of chlorpyrifos in eggshell thinning, we are unable to make any interpretation.
Nevertheless, the presence of chlorpyrifos residue in the eggs is a matter of concern since its metabolite is a proven reproductive toxicant,” the study stated.
‘Pesticides interfere with calcium supply’SMuralidharan, the incharge director of SACON, said, “Use of certain pesticides results in reduced calcium metabolism.
It interferes with supply of calcium that is essential for eggshell formation.
If the eggshell is thin, it will be crushed as soon as the mother sits on it for hatching and will definitely reduce the population of sarus cranes.” Muralidharan, who was also the principal investigator in the study, said that pesticides also result in the death of the birds.
The study said that it could indirectly harm the already endangered bird by reducing its food base.
“It is a fact that birds have the tendency to skip breeding if they do not perceive food security to raise chicks,”it said.
Also, there is a huge possibility that it ingests pesticides while feeding on treated seeds.
Of the 15 species of cranes found in the world, six are found in India.
Only sarus crane (Grus Antigone) is a resident species.
The highest numbers of observations of sarus crane were recorded in the districts of Ahmedabad (39%) followed by Anand (36%), and Kheda (11%).
The study states that the calculated population was estimated to be around1,788.
The study states that “tissues of seven birds collected from three districts for toxicological investigations.
The presence of chlorpyrifos, HCH, DDT, endosulfan and heptachlor were detected frequently.
While endosulfan and heptachlor were the least-detected pesticides, chlorpyrifos was detected more frequently in the tissues.” A total of 179 food samples of sarus crane comprising rice paddy, wheat, fish, and insects were collected and 42 pooled samples were analyzed for pesticide residue.
Among the 67 pesticides analyzed, 12 pesticides were detected and of these chlorpyrifos was the most frequently detected pesticide followed by thiamethoxam.
While 104 samples of soil were collected from nesting and congregation sites, 60 pooled samples were analyzed for residues of pesticides.
Of the 67 pesticides for which analysis was done, 23 pesticides were found at varying levels.
The study suggested, “It is adequately clear that problems due to pesticides exist at varying magnitudes in the state.
Advising complete halt on chemicals might be the easiest recommendation, but practice may not be possible at once.”