Researchers think they know what kills London's iconic sparrow | Science

Once a common sight around London, the house sparrow (Pbader domesticus) populations have been declining for decades; They are down 71% since 1995. Now researchers think they know why: a disease transmitted by mosquitoes called avian malaria.

Scientists have collected data over 3 years from 11 sparrow colonies around London, where birds breed. They counted each year the raw number of birds and collected blood and feces from a number of individuals.

7 of the 11 colonies lost birds and about 74% of the sparrows were avianPlasmodium Relictum). It is the highest parasite infection rate among all wild bird populations in northern Europe, researchers report Royal Society Open Science. Avian malaria could lead to declines in Western Europe, North America and India, the team added.

As with other forms of malaria, avian malaria spreads when mosquitoes bite birds and feed on their blood. The disease can lead to infections that can be fatal for the birds and these can transmit the infection to their offspring. The team found that most sparrows were parasite carriers, but the amount of parasites detected in each bird's system was significantly higher in declining populations, particularly among the younger ones.

Scientists do not know why avian malaria is particularly prevalent among house sparrows, but they say more research could provide clues.