Shorebird assemblages respond to anthropogenic stress by altering habitat use in a wetland in India

Shorebirds are globally experiencing declines due to habitat loss and anthropogenic disturbance. The Central Asian Flyway hosts significant shorebirds that winter in the Indian subcontinent. The current study examined the shorebird assemblages of Kadalundi-Vallikkunnu Community Reserve, an internationally important estuarine wetland in southwestern India, to determine changes in their assemblages in relation to habitat alterations. We conducted point counts from 2005 to 2012 in mudflats, mangroves, sandy beaches and shallow water areas in Kadalundi-Vallikkunnu Community Reserve. This study measured physicochemical variables as a proxy for anthropogenic change experienced as a result of rapidly increasing human populations combined with development. We examined rainfall data during the study period to determine associations with shorebird abundance. Stepwise linear regression showed that total nitrogen and rainfall were significantly related to shorebird abundance (bird count = 306 + 213 NO3--1.13 rainfall, F = 31.20, p < 0.001). High rainfall in a given year (one-way ANOVA F = 19.91, p < 0.001) and the previous year resulted in lower shorebird counts (one-way ANOVA F = 16.01, p < 0.001). Shorebirds declined during the study period and habitat use shifted significantly from mangroves and mudflats to sandy beaches (one-way ANOVA, F = 2.18, p = 0.034). Shorebirds also exhibited a gradual decline in diversity. We conclude that altered nutrient content in this wetland resulted in changes in the prey base in the four habitat types. Shorebirds responded to these changes by increasing the use of less preferred habitat (sandy beaches). The anthropogenic influences on the wetland are large (waste disposal, sand mining, disturbance due to development) and continued pressure may result in further decline of shorebird assemblages. The results from this study indicate that certain anthropogenic disturbances, such as waste disposal and sand mining, should be reduced to maintain and improve the integrity of this wetland.