Updated: Aug 12, 2021
Out of all the culprits behind House Sparrow decline, possibly the most niche curve-bender is the gem in the crown of Britain’s urban birdlife that is the Eurasian Sparrowhawk.
Sparrowhawks are lithe, speedy raptors of woodland rides, coppice and increasingly, urban/suburban gardens. The male is slightly smaller than a Kestrel, with blue/slate gray upperparts, and a beautifully rippled russet red and cream underside. The females are larger (around 20% usually) and are coloured a more ‘sensible’ dusty charcoal brown, and brown and white barring below. Both sexes however are united by their piercingly bright, almost neon yellow/orange eyes.
Once viciously persecuted, Sparrowhawks have recently bounced back, thanks to legal protection and the withdrawal of certain types of toxic Pesticide, which accumulated in their insides via their prey. A glut of relatively competition-free prey, warmth from buildings, and secure nesting spaces have also enticed them into our towns and cities with open arms. Recently whilst walking in Portsmouth, the 2nd most densely populated area in Britain, I saw a gorgeous pair of them fly right over the city centre, my first ever Sparrowhawk pair!
Right behind Sparrowhawks, Kestrels, Hobbies (in my opinion the most gorgeous falcon to grace our skies, famed for its appetite for Dragonflies) and Red Kites have also been colonizing our urban areas, which the RSPB suggests is largely down to House Sparrows (as a vital food source). Personally, I find this an incredibly exciting thought.
House Sparrows have always been a very urban bird, and evidence such as this suggests they could actually act as a bridge allowing other wildlife to cross over into our urban landscape and rewild it – definitely something I’d like to research more!
Anyway back to Sparrowhawks!
Alongside Cats, Corvids and even Grey Squirrels, Sparrowhawks are currently under scrutiny for their potential part to play in House Sparrow declines. And it is safe to say that they hunt House Sparrows more than any of the other culprits (bar cats) males in particular specialising on fly-by assassinations on small birds like Sparrows and Tits (the females targeting larger birds – as big as pigeons!). And, with their recent move into urban areas, it’s entirely plausible they’re taking a bite out of urban populations.
The theory in its entirety is that, when our cities and towns became so urbanized that predators like hawks initially couldn’t follow sparrows in colonizing them, House Sparrows have been relatively free from predatory birds (bar the odd Crow) so lowered their guard, so that today they don’t fear Sparrowhawks as much as they should, having lost that inherent fear. So, over the past years where Sparrowhawks and other birds of prey have colonized our urban areas, they’ve been bolder and more sluggish, perfect prey, so more have ended up hunted.
However, while this is likely true, if Sparrowhawks are a significant cause behind the House Sparrow’s demise, why is it that as Sparrowhawks have been increasing (from the early 2000s onwards) the decline of House Sparrows has actually slowed, levelling off locally (although BGBW results show they’re still declining at several % annually). And, when the House Sparrow first started heavily declining in the 1970s, Sparrowhawks were absent from urban areas, heavily exploited and dying out?
If you search up “House Sparrows and Sparrowhawks” into Google, an overwhelming amount of searches that come up will be of one news story, whereby a scientist from the BTO allegedly said that Sparrowhawks were possibly the reason House Sparrows are in decline. However, we know there’s a multitude of reasons for this (just take a glance of my Twitter feed!) and delving into the BTO’s research, their House Sparrow mortality survey ironically found that in areas where Sparrowhawks were present, there were actually more House Sparrows!
Of course, this could be because the areas Sparrowhawks choose to live in are in healthier condition, and have larger amounts of food, as opposed to where they aren’t found, where pollution etc likely kills huge numbers of House Sparrows, causing their numbers to go down more than any Sparrowhawk-induced decline. But as is often the case we sadly don’t have enough research to say whether or not that’s true.
In summary, Sparrowhawks are almost certainly taking a small chunk out of some local House Sparrow populations, while they inherit that fear of them again, and the species adjust to each-other again, however they are not one of the main drivers of House Sparrow decline, and once House Sparrows have started inheriting that fear again, any populations that have been affected will likely bounce back. And, above all else, even if declines in House Sparrows were heavily induced by Sparrowhawks, it’s part of nature, and I personally don’t think we should interfere, as one of the main flaws in our modern conservation model is zeroing-in so much on one species, we forget all the other characters in its ecosystem.
(Just a little collection of photographer Lauren Fairfax's encounter with her local Kestrels, another fellow Sparrow hunter!)
Hope you enjoyed! Let me know what you thought/if you’ve heard anything else about Sparrow/Sparrowhawk relations, I’d love to hear it!
Give me an email/message on social media if you have problems with anything, or if you’ve got a question/want to know a bit more, don’t hesitate to get in touch!
Thanks for reading. :)