Dr M. Jayashankar
Birds while feeding ingest soil, sediment and small gravel either accidentally, birds feeding on earthworms or intentionally as a source for minerals, to reduce gastric disturbances or gut acidity, or as grit for aiding digestion. Seed eating birds such as sparrows eat mortar for the grit it contains as they lack teeth unlike their predecessors the reptiles (except turtles and tortoises). Small hard pieces of stone/sand in the mortar serve as abrasive digestive helpers in their muscular gizzard. The grit help break down hard foods such as seeds and the hard exoskeleton of some insects and in some cases the same serve as grit. Research in this regard indicates in addition to variation in the amount of grit ingested each day, species vary in their preferences based on grit size, shape, surface texture and color. It has also been reported that great variation in grit selection among individuals is based on seasonal diet composition, age and nutritional and reproductive status.
Arunachal Pradesh Regional Centre of Zoological Survey of India campus in Senki valley has sizeable population of tree sparrow scientifically named Passer montanus. They were observed pecking grit from the walls of garage and parking area, also old under constructed buildings in the surroundings. The tree sparrow is an old world sparrow with a broad geographical range, and is generally found throughout western, central and southern Europe, east into Asia to the Pacific coast of Russia and south to Indonesia. Measuring 14–15 cm and weighing 17–30 g, it is a monomorphic species, both sexes similar with a rich chestnut-brown head and nape, a clear bean shaped black spot on white cheeks, and a white collar. Flocks of 10-30 birds were observed foraging on low herbs and grass seeds in the office garden and pavements and foot paths in the vicinity. The anthropophilic birds frequented households in the neighborhood pecking on spilled grains and forage on insects in patches of corn grown in the backyard. The pecked grit also serve as a nutrient supplying calcium carbonate a necessary component for egg shell architecture, needed for the female birds to produce viable eggs. The observation period coincides with the breeding season of the species April-May producing clutches of two to seven eggs. These loose colony nesters, construct a dome shaped nest in a hole in a tree, earth bank, cliff or artificial structure, sometimes in the base of a large nest of other birds like heron or crow using dried grass and rootlets, lined with feathers and animal fur. To avoid damage to infrastructure, alternatives to peck in the form of manufactured picking stones are now available in market in many countries.
Reports of declines in this species in its European range may be a result of changes in agricultural practices such as the increased use of pesticides and herbicides and the autumn sowing of cereals which have lead to decreases in their food supply.Unfortunately, the route of chemical exposure including lead in many ecological risk assessments is the ingestion of chemicals by birds on or in sediments, soil and small gravel (i.e., grit).Although recognized as Least Concern Species, Passer montanusare integral part of ecosystem occupying primary consumer level as granivores and secondary consumer level as insectivores, game hunting is still a threat and awareness in this regard is warranted considering the worldwide campaign with March 20thobserved as the World Sparrow Day to save the sparrow and also to bring them back to their habitat. India is home to five different species of sparrow in addition to the tree sparrow, House Sparrow (Passer domesticus), Spanish Sparrow (Passer hispaniolensis), Sind Sparrow (Passer pyrrhonotus) and Russet Sparrow (Passer rutilans).However, the house sparrow are most common, abundant and widespread. Conservation efforts are on in raising awareness about the declining population of house sparrows. In a number of areas, nest box schemes have been started to provide the tree sparrow with suitable nesting sites. The Convention on Biological Diversity (CBD) calls for action and policy to conserve urban biodiversity, maintain the ecological functioning of cities and offer citizens opportunities to experience and learn about local wildlife in cities worldwide. “With the growing awareness of the value of biodiversity and ecosystem services, cities with rich native biodiversity should ensure that their biodiversity is conserved. Cities with impoverished biodiversity should pursue enhancement, restoration, and reintroduction efforts to increase native biodiversity”. Remember the Door Darshan era song of ‘ek Chidiya Anek Chidiya’ its chirrup and vivid flight, let’s conserve them.
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