The species of house sparrows (Passer domesticus) is one of the most common and familiar species of small singing birds, having conical bills, and feeding chiefly on seeds and insects. This species of birds is noted for its familiarity, voracity, attachment to its young ones, and fecundity. It has co- evolved with man, and is found in almost all parts of world, including India, though, most chiefly, in Europe. But, now-adays, this species of birds is slowly and gradually becoming uncommon or endangered. Its population is declining day—by-day with much speed, which is a matter of great concern for the whole Earth. These house sparrows, in fact, are the bio-indicators of the environmental health, and so, their disappearance is a warning signal to all of us. The vanishing of sparrows has widely been reported, from all over the world, and the condition is aggravating more and more with the passage of time. Now, the question arises regarding the main factors responsible for such a misfortunate happening. This research paper, therefore, attempts at explaining all those numerous reasons behind the dramatic reduction in the population of house sparrows in last few years. At the same time, it purports at finding solutions to those hurdles which have put a question marks on the long-lasting survival of this tiny creature on the Earth. Obviously enough, this investigation report is extremely significant in order to make people aware of the different causes behind the decline in the population of sparrows and to provide preventive measures among them so that their protection and conservation can be ensured immediately.