I still fondly recollect my childhood days when house sparrows used to be a very common bird in our neighbourhood and how my grandmother used to feed them.
Not anymore, now once common bird appears to be a fast disappearing species due to various reasons like declining green cover in cities, rising pollution. To raise awareness on this issue and to save the sparrows, 20th March is observed as World House Sparrow Day since 2010.
I did some study about this trend of decline in sparrows. In some of the asian countries, the house sparrow was eradicated on the ground of being a crop pest. Interestingly, the same sparrow was introduced to control pest in America and Australia to reduce dependence on chemical alternatives.