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Can We Have Your Sparrows?

By Humphrey Q. P. Crick and Mike P. Toms
 

A view from Britain

In Britain, House Sparrows are a native species, but for many years until just recently, they were considered disease-carrying or agricultural pests. Flocks of thousands of these birds could descend on fields and destroy substantial areas of ripening grain. In the 18th and 19th centuries most parishes had “Sparrow Clubs” that sought to destroy as many sparrows as possible. “Sparrow Money,” a bounty paid for dead birds and eggs, could be substantial. For example, in one parish in 1827 alone, 72 pounds sterling, 5 shillings, and 8 pence were paid in Sparrow Money for about 20,000 birds—equivalent to around $2,000 in present-day money. Sparrow pie was a regular country dish until 1914. It was said that “the sparrow is excellent food, and a great restorer of decayed nature [health].”

But things have changed. In the 1990s it became clear that House Sparrow numbers were falling rapidly. The Common Birds Census, a volunteer-based census organized by the British Trust for Ornithology (BTO), found that House Sparrow numbers in the countryside declined by 53 percent between 1976 and 2000. The BTO’s Garden Bird Feeding Survey showed that populations in rural and suburban gardens had remained relatively stable until 1983 (Figure 1). Since then, they have declined by 48 percent in rural gardens and by 60 percent in suburban gardens.

Like the Cornell Lab of Ornithology, the BTO (www.bto.org) has a fantastic volume of historical citizen-science data gathered from all over the country to analyze. We were able to review the information from breeding and wintering censuses, nest records, and bird banding. We showed that populations were declining fastest in the sparrow strongholds in southeast England and that sparrows were coming into gardens sooner in the winter than they used to, suggesting that food supplies in the countryside are poorer than they used to be. Analyses combining information on numbers, breeding performance, and survival showed that although the declines in numbers appeared to be due to declines in the survival rates of birds in the first year of life, improvements in breeding performance had helped to halt (although not reverse) the decline.

We concluded that the declines of sparrows on farmland in Britain are likely to be due to farms that are much more “hygienic” now than they used to be; grain stores are sealed from the birds and less grain is spilled. However, the reason for the declines in towns is still a mystery. The populations in towns are patchily distributed, with colonies of birds separated from others by empty areas that look, superficially, no different from the occupied areas. Possible causes for the declines in towns include predation by domestic cats and sparrowhawks; loss of weed seeds through development of waste ground; changes in the suitability of food at feeding stations; air pollution; disease transmission; use of pesticides in gardens; and loss of nest sites.

To learn more about habitat choice and factors that may influence the distribution of sparrows within towns, the BTO launched a special survey based on the efforts of our 16,000-strong Garden BirdWatch citizen-science volunteers, a program inspired in part by the Lab’s Project FeederWatch.

We have selected a sample of randomized 500 m x 500 m squares within towns of different sizes and asked our volunteers to map the habitats and to count and record sparrows in 2003 and 2004. The response has been great—around 1,500 volunteers have taken part in the study and 12,000 more have returned questionnaires about how sparrows use gardens. We hope to announce the first results soon.

In Britain we are worried about our sparrows. We know that in North America they are introduced pests, but we could do with some of yours! We think our story has some important lessons for programs that monitor wildlife. In the 1960s and early 1970s, we thought that sparrows were just a nuisance—they were so numerous and difficult to count that we asked our volunteers not to count them on our Common Birds Census between 1962 and 1974. What fools we were! We lost valuable information at a stage when they were doing well, leaving a big gap in our knowledge. The lesson is surely that we need to monitor all our wildlife, particularly the common species. It is these common and widespread species that are perhaps the best barometers of the health of our own environment, as we, too, are a very common and widespread species.

Humphrey Q. P. Crick is the head of the demography unit at the British Trust for Ornithology, and Mike P. Toms is the organizer of Garden BirdWatch.

This article originally appeared in the Winter 2004 issue of BirdScope.

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