New research has shown that house sparrows may be pre-disposed to suffering from winter food shortages.
New theories regularly crop up in the search to find the reasons behind the demise of the house sparrow (Passer domesticus
). Everything from pigeons
to garden makeovers
have been implicated and the truth is probably that many factors are involved. One theory that has gained a lot of credence is that sparrows have suffered from changes in agricultural practices which have led to shortage of food in the winter. However, experts could not explain why they have declined more than other species which also depend on the same winter foods. But after weighing 10,000 sparrows over a number of years, Scottish scientists now believe they have discovered a vital clue that could unravel this mystery.
Results show that house sparrows fail to prepare effectively for the low food supplies and freezing temperatures during the winter months. Instead of eating extra before colder weather, sparrows retain their sleeker shape to allow them a better chance of fleeing predators - despite the disadvantage of having a low body weight when the temperatures drop. This pattern makes sparrows even more vulnerable than other species to environmental changes that reduce food supply, such as cleaner urban environments or agricultural intensification. Dr Ross MacLeod, of the department of evolutionary and environmental biology at Glasgow University, said: "It is the sparrow's innate vulnerability to environmental change that can help us understand why they have so far been affected more than other species."