The end of summer always sees a peak in the number of house sparrows visiting my garden, as the young from this year’s breeding attempts join the local flock at my feeding station. Judging by the numbers of young birds present over recent weeks, I suspect that it has been a good breeding season despite the slow start to the year.
More widely, there is also evidence that house sparrows may be doing rather better than they have for a while. The weekly observations made by the BTO’s Garden BirdWatch volunteers (www.bto.org/gbw), for example, suggest that the long-running declines in the house sparrow’s fortunes have levelled off. Of course, any improvement needs to be viewed in the context of several decades of decline – house sparrow populations have fallen from 12 million breeding pairs in the 1970s to just under 6 million breeding pairs now.
The reasons for the longer-term decline are unclear, at least within the urbanised landscapes where the bulk of the breeding population is to be found. Loss of nest sites and feeding opportunities are likely to be the main drivers behind the decline but other factors, such as increased levels of competition, predation and pollution, may have also played their part. Although adult house sparrows feed on seeds, they require invertebrate food for their chicks and this resource is likely to have suffered as gardens have become more tidy, with greater use of pesticides and the preference for exotic plants and shrubs over native ones. Interestingly, a study carried out in urban Bristol showed that house sparrows fared better in areas of lower quality housing than they did in more middle class housing – a reflection, perhaps, of the different levels of house and garden maintenance that come from inequalities in household income.
Just as the reasons behind the decline have yet to be unravelled, it is unclear why things might have improved over recent years. Is the message about wildlife-friendly gardening now hitting home, or could it be that house sparrows now face less competition from a greenfinch population hit by the 2006 outbreak of disease? More work will be needed to find out but, for my part, I am delighted to have my sparrows back.