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Sparrowhawks are a common sight in the UK and Ireland, often spotted in woodlands and gardens. Some people see the beauty in the sparrowhawk, while others worry about their impact on songbirds. So are sparrowhawks a privilege or a pest in gardens?

Sparrowhawks: friend or foe?

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. They are now one of the most widespread birds of prey in the UK, but they were once close to extinction and experienced a significant decline during the 1950s and 1960s. While the loss of songbirds can be sad to see, sparrowhawks also need to feed and raise young to survive, and by feeding songbirds in our gardens we’ve simply created a concentration of prey for them. We are creating the access to food that these birds need to thrive.

Understanding the impact of sparrowhawks on songbirds

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).
  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 songbird populations

It’s 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 in this species 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 – e.g. the sparrowhawk took a young robin weakened by disease or extreme cold.

Fluctuations in sparrowhawk numbers

Sparrowhawk numbers have experienced declines in the past, at one point leading them close to extinction. The change in population has been through numerous peaks and valleys throughout the years:

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 critical low during the 1970s.

1980s: recovery beings

DDT was banned in the UK in 1984. After this, sparrowhawk populations began to recover. As the effects of the pesticide diminished, there was a noticeable improvement in the success of sparrowhawk breeding.

1990s: steady growth

The sparrowhawk populations rebounded to an estimated 32,000 breeding pairs in the UK. Their numbers continued to grow across most regions of the UK as a result of the ban on harmful chemicals and improved environmental conditions.

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

The presence of sparrowhawks in your garden is an excellent sign of a healthy ecosystem. 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.