I’m sure that all of us have watched the wildlife documentaries on the television that illustrate, in graphic detail, African big cats slaying their quarry. Many people’s perspectives change sharply, however, when the friendly garden robin is nailed by a Sparrowhawk. Witnessing sudden death on your doorstep seems to generate resentment and a desire for revenge. But are Sparrowhawks really the villains that many suppose them to be?

Some people are worried that Sparrowhawks eat too many small birds and cause their population to fall. This is unlikely to happen – long-term scientific studies have shown that Sparrowhawks have no impact on overall songbird populations, and that songbirds were no more common when Sparrowhawks were absent than when they were numerous. The Sparrowhawk population was decimated in Britain, by chemical pesticides entering the food chain in the 1960s and 70s and songbird numbers remained the same in the hawks’ absence.

It is an easy conclusion to draw that Sparrowhawks are responsible for the recent declines in many songbird populations – they are highly visible killers. In theory, if you drastically reduce all the predators, then there should be a lot more songbirds around. Neither the RSPB nor the British Trust for Ornithology (BTO) agrees, and science appears to be on their side. The RSPB explains that “small birds can rear between five and fifteen young in a season, while only one or two need to survive to keep the population stable. The vast majority die before the following breeding season because there aren’t enough nest holes, caterpillars or territories to support such numbers. In the absence of predators, these would simply die of starvation or disease. Predators simply feed on this doomed surplus. Instead of dying in winter from food shortage or disease, the small birds die in all seasons, many from predation.”

This is backed up by studies undertaken by the BTO. During the last 30 years the marked declines in the populations of many British songbirds have coincided with population increases and range expansion of two of their main predators, Sparrowhawks and Magpies. Using long-term census data the BTO has shown that Magpies and Sparrowhawks are unlikely to have caused songbird declines because patterns of year-to-year population change did not differ between sites with and without these predators. Other large-scale changes in the environment, such as the intensification of farming practices, appear to be responsible for songbird declines. More recent work by the BTO has highlighted habitat modification by deer and climate change amongst the causes for woodland bird declines, but there is no suggestion that Sparrowhawks are involved.

It is also worth remembering that Sparrowhawks and songbirds have existed side by side for thousands of years without any detrimental effect on the populations of the songbirds. The number of Sparrowhawks in an area is naturally restricted by food availability and the number of suitable nesting sites. If songbird numbers increase, Sparrowhawk numbers increase. If songbird numbers go down, so do Sparrowhawk numbers. This very close and sensitive link between Sparrowhawks and their prey make the hawks a monitor of the health of the ecosystem. The very presence of Sparrowhawks is evidence of a healthy environment with strong populations of songbirds.

Sparrowhawks remove the most vulnerable individuals, so those with the best escape tactics survive. This brings immense stability to the system, as the fittest and healthiest individuals survive. These are much more likely to breed successfully themselves and produce a greater number of fitter young birds that have a better chance of survival. If habitat is diverse and contains plenty of food and cover for small birds, the balance is tipped further in favour of the prey. Once they have been spotted by their prey, Sparrowhawks only have about three seconds to grab the prey before it escapes. Because the hawk is quite easily seen, and small birds warn others to fly for cover with calls, only about one attack in ten results in capture.

However much you dislike Sparrowhawks, it is hard to find facts that support claims that they are the culprits for songbird declines. Sparrowhawks use your garden in the same way as Blue Tits and finches, and it is a magnificent sight to watch finely tuned predators hunting at such close quarters. In case you still thought that Sparrowhawks were profiting whilst the local songbird populations were in decline, the BTO's latest report may interest you. The results from their annual Breeding Bird Survey show a decline in excess of 20 per cent in Sparrowhawk numbers over the last decade.

Photographs by courtesy of Geoff Harber (1) and Duncan Jennings (2)