- Tree-nesting waterbirds, such as the woolly-necked stork, often have a fragile relationship with farmlands, given that their survival depends on the retention of trees amidst crops. Negative attitudes, hunting, and monoculture farming have limited nesting to ‘wilder’ habitats around the world.
- However, large breeding populations of woolly-necked storks in Haryana are found even in densely populated villages and towns that are heavily dependent on agriculture.
- Further research shows that nests built by woolly-necked storks are frequently being reused by dusky eagle-owls.
As bird populations across the globe steadily decline, the woolly-necked stork is thriving in India, particularly in the northern state of Haryana. According to a recent study, large breeding populations of this understudied species can even be found in densely populated villages and towns of the state, which has been predominantly an agricultural landscape. The findings support evidence for the revision of their IUCN Red List status from ‘vulnerable’ to ‘near-threatened’.
Tree-nesting waterbirds such as the woolly-necked stork (Ciconia episcopus) often have a fragile relationship with farmlands, given that their survival depends on the retention of trees amidst crops. In places such as North America, waterbird colonies in human-dominated areas are regarded as a nuisance that require ‘removal’. Large-scale mechanised monoculture farming that necessitates deforestation and removal of wetlands, along with hunting activities, have largely limited waterbird nesting to wetland reserves, protected riverine forests, and inaccessible islands.
Tropical countries such as India tell a different story. “For the longest time, it was believed that this particular species needed forest reserves to survive. We now know that they prefer irrigation canals over wetlands. The storks use agricultural fields as their major habitats in South Asia where conducive crops, relatively traditional farming techniques, and low hunting activity are key to their proliferation alongside food production,” says K.S. Gopi Sundar, co-chair, IUCN Stork, Ibis and Spoonbill Specialist Group, and co-author of the study.
Nest case scenario
The study, on how traditional agriculture facilitates woolly-necked stork breeding, observed 298 nests in 166 locations from 2016 to 2020 in Jhajjar and Rohtak districts. Both districts have high densities of woolly-necked storks year-round. They also have a network of irrigation canals and community-managed wetlands, with nests found in both. Traditional agriculture where forest patches and individual trees are found amid croplands in these areas, enabling silviculture, harvesting of fruits, woodwork and foraging of livestock.
According to the study, storks nested between May and October every year. The density of nests varied little annually and each year a small proportion of nests (8.16-15.09%) were located on electricity pylons (transmission towers). They were also found within areas of human habitation. The average brood size of 42 successful nests produced a median of three chicks in most years.
“This novel scenario contradicts the narrative regarding the supposed inability of these storks to live with humans in agricultural landscapes. Humans who inhabit South Asian agricultural landscapes do not commonly hunt the non-human residents like in some other countries. This, alongside availability of a wide variety of prey, facilitates multiple species to use farmlands as their primary habitat,” says Sundar.
In addition, most nests observed in the study were not found on the tallest trees (so far assumed to be preferred), but on medium-sized, native rosewood or shisham (Dalbergia sissoo). “The tree is known for its hard wood, commonly used to make yokes and furniture. This particular species has been a part of these farmlands for hundreds of years at the very least. Despite being relatively short, the commonness of this tree species and the absence of hunting by farmers has led to this tree being the most routinely used for nesting by the single-nesting woolly-necked storks,” says Sundar.
Some nests were also found on two tall trees – the native Ficus religiosa and the exotic Eucalyptus sp.
What came as a surprise was that nests built by woolly-necked storks were preferentially reused by dusky eagle-owls. “Large raptors, including owls, frequently reuse nests of other species, but their reliance on nests of a single species is unusual,” says Sundar, who co-authored another study on the relationship between the two species.
Dusky eagle-owls were noted to reuse the nests of other birds after the nest-builders’ chicks had fledged. The study recorded the owls reusing two nests of the Indian spotted eagles (Clanga hastata) and one of the red-naped ibis (Pseudibis papillosa). However, they reused as many as 20 nests of the woolly-necked storks.
Both the woolly-necked storks and the dusky eagle-owls reused some nesting sites each year, but the latter were more likely to reuse sites.
The owls, however, differed in their choice of trees for nesting. They preferred the Eucalyptus sp., and reused fewer nests on Dalbergia sissoo and Ficus religiosa. This suggests that the species favoured taller trees for nesting. Thus it was concluded that the protection of trees that the storks nested on could potentially support the breeding of the owls.
There are several waterbird species in Asia and Africa that are of global concern to conservationists. The status of many of them is based largely on the assumption that farmlands are detrimental to their well-being, despite the absence of surveys in such areas in the tropics.
However, as research now shows, common artificially-made features in South Asian farmlands such as irrigation canals, tanks and reservoirs, could potentially be harnessed with minimal additional expenditure to aid long-term conservation. Researchers suggest that a diverse toolkit be assembled, compiling locally relevant mechanisms that support biodiversity amid cultivation.
In Haryana, for example, farming methods, irrigation system, and cropping patterns proved to be conducive to maintaining breeding stork populations. This is similar to recent observations from lowland Nepal where farmers follow similar traditional farming. “There is no doubt that the combination of agroforestry, appropriate seasonality (wet monsoons when nesting occurs), conditions that support prey (for example, flooded fields attract amphibians, insects and reptiles), and long-standing farming practices have provided stable conditions over centuries, and helped create the most productive stork population in the world,” says Sundar.
Banner image: Two woolly-necked storks crossing the road in north India. According to research, irrigation canals, tanks and reservoirs can support long-term conservation with minimal expenditure. Photo by K.S. Gopi Sundar.