Where did all the sparrows go?

The sparrows have disappeared completely from the cities at least four years ago in Britain, as mobile phones grew in popularity. Third generation (3G) mobile phones were introduced in 2003, and there were over 65 million users in the UK by the end of 2005, more phones than people. Did mobile phone transmitters cause the sparrows to disappear ?

Scientists at the Research Institute for Nature and Forests in Brussels, Belgium, have produced the first evidence that mobile phone base stations are affecting the reproductive behaviour of wild sparrows. This finding comes as mobile phones are held suspect in the massive collapse of bee colonies all over the United States and Europe (Mobile Phones and Vanishing bees)

Joris Everaert and Dirk Bauwens wanted to know if the low intensity microwave radiation from mobile phone base stations has any effect on the number of house sparrows during the breeding season. They identified 150 locations distributed over six residential districts in Gent, Sint and Niklaas in the province of East Flanders, where they counted the number of male house sparrows and measured the strength of electromagnetic radiation from base stations.

The study areas were similar, with abundant hedges, bushes, and other vegetation between the houses, and one or more GSM (Global System for Mobile Communications) base stations nearby. All locations were along small roads within the residential areas and at variable distances from the nearest GSM (mean 352 m, range 91-903 m, about 90 percent at 100-600 m). On days when the weather was favourable, so male sparrows would be out singing, the researchers went to each location between 7 and 11 am, and using binoculars, counted the number of male sparrows within a radius of about 30 m for a period of five minutes.

Simultaneously, they measured the maximum value of the electric field strength (in V/m) from the GSM 900 MHz and GSM 1800 MHz base station antennas during 2 minutes for each frequency band, using a portable calibrated high-frequency spectrum analyser.

Everaert and Bauwens found that the number of house sparrow males varied between zero and four at the different locations. The measured electric field strengths were seldom higher than 1V/m, and most often well below that value. Nevertheless, the spatial variation in the number of house sparrow males was negatively and highly significantly correlated to the strength of electric fields from both the 900 and 1800 MHz frequency bands and from the sum of these bands. This negative correlation was very similar within each of the six districts, despite differences in both the number of birds and radiation levels.

Fewer house sparrow males were seen at locations within relatively high electric field strengths of GSM base stations. For example, the mean number of male sparrows varied from 1.9 at the combined field intensity of 0.13 V/m to 0.8 at a combined field intensity of 0.247 V/m.

The results, though preliminary, do support the hypothesis that long-term exposure to higher levels of radiation negatively affects the abundance or behaviour of house sparrows in the wild. Fewer males singing would mean less breeding success.