Table of Contents 1.

Sparrowhawks are now a common sight in the UK, and are often spotted in woodlands and gardens. Some people see the beauty in this bird of prey species, while others worry about their impact on songbirds. So are Sparrowhawks a privilege or otherwise in gardens?

Sparrowhawks: friend or foe in the garden?

This might be one of the more controversial topics we’ve covered in our bird of the month series, as whilst many of you reading this will rejoice in the spectacle of a Sparrowhawk arriving at high speed in your garden in the pursuit of prey and brilliantly dodging obstacles such as a rotary clothes line along the way, some of you will be less than enthused. Of course the usual reason for the latter position, is that Sparrowhawks kill and eat the very same songbirds we’re all feeding and, in so doing, trying to improve their breeding success. But Sparrowhawks also need to feed and raise young to survive, and by feeding songbirds in our gardens we’ve simply created a relative concentration of prey for them. So in this respect it’s down to us, but rather than see that as a negative we should see it as a positive.

Many centuries ago and in a landscape of plentiful mature woodland and minimal urbanisation, all of this would have been going on unseen and in an entirely natural way. But the UK isn’t like that anymore, and the vast majority of us live in a man-made landscape and one where acres of ancient woodland once stood. Of course the Sparrowhawk doesn’t know about any of this and just instinctively sees the mosaic of gardens as the same sort of hunting territory it would have had in ancient times.

Understanding the impact of Sparrowhawks on songbirds

looking at this objectivity rather than emotionally, it’s important to squash the myth that Sparrowhawks have a measurable negative impact on national songbird populations – they don’t.

Studies have shown that:

  1. Sparrowhawk populations are partly linked to songbird populations in a relative sense – i.e. if songbird populations go up then so do sparrowhawk numbers, and if they go down then so do Sparrowhawk numbers. This is referred to as ‘predator-prey dynamics’ and is an accepted principle of ecology. 
  2. Sparrowhawks may change the way a songbird meets its fate but doesn’t affect the numbers meeting their fate.

The naturally high mortality rates of songbirds 

It’s also important to understand that songbirds have high fatalities rates, which is why they produce large broods. Taking the Robin as an example, a pair would typically have two broods per season but may have three, with four to six young in each. So at the very maximum end of that scale, if all the young survived until the next breeding season and both adults did as well, then two birds have suddenly become 20. This is a position which clearly wouldn’t be sustainable, as on a UK scale that equates to 6.7m pairs becoming 67m in one year!

As songbirds like Robins have naturally high mortality rates, some of the young would die of other causes, including a lack of food, a very cold spell of weather, disease, predation by cats, hitting a conservatory window etc. If Sparrowhawks were living in the same area as our hypothetical pair of Robins, then the averaged-out effect would simply be they were responsible for some of the fatalities instead of some of those listed. 

Changes in Sparrowhawk numbers over the decades 

Sparrowhawk numbers have experienced declines in the past, at one point leading them to being close to extinction in the British Isles. The followings outlines changes in population since the 1950s:

1950s – 1960s: population decline

The widespread use of the pesticide DDT on farmland led to a dramatic decline in Sparrowhawk populations. The chemical caused eggshells to thin, leading to reproductive failure and many Sparrowhawk chicks didn’t survive.

1970s: continued low numbers

DDT was still prevalent in Sparrowhawk environments, meaning that the populations remained critically low during the 1970s.

1980s: recovery starts

DDT was banned in the UK in 1984, and after this Sparrowhawk populations began to recover as a result of more successful breeding.

1990s: steady population growth

The Sparrowhawk population rebounded to an estimated 32,000 breeding pairs in the UK. 

2000s: small declines

Some regions of the UK have experienced small declines in Sparrowhawk populations, potentially due to localised environmental changes, losses of habitat, or higher competition for food.

Present: population stable

At present, Sparrowhawks maintain stable numbers across the UK, although they are not especially in abundance. They are a key part of the natural ecosystem, with populations fluctuating depending on the availability of prey.

Celebrating the natural balance of nature

So next time a Sparrowhawk visits your garden, not only can you celebrate its arrival, but also rest assured that it isn’t negatively impacting the numbers of songbirds you’re also attracting by feeding them.