SPARROWHAWK (ACCIPITER NISUS)
To some, a swift demon snatching defenceless birds from
their garden feeders. To others, an exciting
reminder of the wild on their doorstep. The sparrowhawk Accipiter nisus embodies the attitude of nature red in (beak) and
claw.
Sparrowhawks usually make a surprise appearance, often a fleeting
glimpse as one shoots by. In flight, the sparrowhawk has a distinctive outline
with short, broad wings and a long oblong tail. When resting, their glaring yellow
eyes are another striking feature. Sparrowhawks are usually silent, but are
often heralded by the alarm calls of other birds.
Female sparrowhawks are 25% bigger than males, a record breaker amongst birds1. This helps avoid competition for prey. Males hunt small birds like tits, finches and sparrows whilst the females take thrushes, corvids and pigeons.
Their colouring is also different. The male casts a handsome figure with a slatey blue back and fine orange bands across his chest whilst the female has a browner back and chest bands.
Sparrowhawks are woodland birds by nature, but the planted
trees and bird communities of gardens are a good substitute. Over 90% of their
prey is live birds, with small mammals (including bats), carrion and insect snacks occasionally
on the menu2. In general, sparrowhawks aren't fussy, taking
whichever bird is readily available. In his 30 year observations, J.H.Owen
noted 57 prey species2.
The sparrowhawks’
hunting strategy is to coast around behind cover3 (Trees, hedgerows,
fences and even people on the streets*) before bursting into a surprised group
of birds and snatching its prey with long, lobed talons perfect for gripping a
moving target. If given the slip, the sparrowhawk’s specialised wings and tail
come into action steering over, under and between branches at speeds of up to
50kph4. The hawk despatches its prey with talon squeezes or eats it
alive depending on which is easier. Sparrowhawks are even known to drown preyᵻ.
The forensic signs of a sparrowhawk kill are scattered, plucked feathers and
missing head and/or breast meat, the raptor’s choice delicacies.
The sparrowhawks hunting skill has shaped its scientific name (Accipiter from accipere, to grasp1) and has been honoured in human weaponry. The musket (an early hand gun) was named after the falconer’s term for the male sparrowhawk- both being small, fast and deadly5.
Sparrowhawks are such infamous predators of other birds that
they have been scapegoated for causing songbird declines. The sparrowhawk’s
recovery from persecution by gamekeepers and poisoning by DDT (a pesticide that
builds up through the food chain) since the 1960’s coincided with the decline
in small woodland and farmland birds6. It is easy to put two and two
together and some organisations such as the “Songbird Survival” did (and partly
still do) just that7.
But the evidence does not support this. Studies show that songbirds are thriving where sparrowhawk populations are highest8, and sparrowhawks act as ‘compensatory predators’9, meaning they only kill prey in numbers which would have died from natural causes anyway, such as harsh winters. This makes obvious sense since the predator relies on good prey populations, and depleting their food source would doom the sparrowhawks in the long run. In other words, most small birds survive to breed in the same numbers whether or not sparrowhawks are around, and human-caused habitat loss and land management changes are far greater causes of songbird decline7,9. Even around garden feeders which often become sparrowhawk magnets, birds adjust their behaviour to cope- feeding little and often to avoid becoming full and sluggish targets9.
But the evidence does not support this. Studies show that songbirds are thriving where sparrowhawk populations are highest8, and sparrowhawks act as ‘compensatory predators’9, meaning they only kill prey in numbers which would have died from natural causes anyway, such as harsh winters. This makes obvious sense since the predator relies on good prey populations, and depleting their food source would doom the sparrowhawks in the long run. In other words, most small birds survive to breed in the same numbers whether or not sparrowhawks are around, and human-caused habitat loss and land management changes are far greater causes of songbird decline7,9. Even around garden feeders which often become sparrowhawk magnets, birds adjust their behaviour to cope- feeding little and often to avoid becoming full and sluggish targets9.
Sparrowhawks themselves are not invincible. They must watch
their own backs for larger peregrines Falco
peregrinus and goshawks Accipiter gentilis
and harsh winters that kill off small birds lead sparrowhawks to starve in turn10.
Sparrowhawks are short lived for a raptor, and less than half their breeding
attempts produce fledglings10. Like most predators, they simply
cannot reach damaging numbers.
It is time we stopped viewing sparrowhawks as detached murderers of our garden treasures and recognise them as yet another beautifully adapted predator inextricably linked with the fate of our smaller birds. It is a testament to changing times that the sparrowhawk has managed to become so common around our homes.
It is time we stopped viewing sparrowhawks as detached murderers of our garden treasures and recognise them as yet another beautifully adapted predator inextricably linked with the fate of our smaller birds. It is a testament to changing times that the sparrowhawk has managed to become so common around our homes.
*One of my most memorable encounters with a sparrowhawk was
when one flew past chasing a sparrow just inches from my face as a child!
ᵻThis
may seem barbaric and upsetting to our eyes, but as with all predators, the
sparrowhawk acts on efficiency, not moral code. Is a song thrush bashing a live
snail on a rock any less ‘barbaric’?
References
1- R.A. Robinson. (2005) BTO
BirdFacts: profiles of birds occurring
in Britain & Ireland:Sparrowhawk Accipiter nisus. Available from:
http://blx1.bto.org/birdfacts/results/bob2690.htm
2-J.H. Owen. (1932) The Food of the Sparrow-Hawk. British
Birds,26, 34 – 40. Available from: http://www.britishbirds.co.uk/search?model=pdf&id=1444
3- Dominic Couzens. (2012) Garden Birds Confidential. Bounty
Books.
4- RSPB. (2013) Birds
by name: Sparrowhawk: Hunting. Available from: http://www.rspb.org.uk/wildlife/birdguide/name/s/sparrowhawk/hunting.aspx
5- Fransesca Greenoak. (1979) All the Birds of the Air. A.
Brown and Sons.
6- BTO. (2013) Bird of
the Month: Sparrowhawk. Available from: http://www.bto.org/about-birds/bird-of-month/sparrowhawk
7- Songbird Survival. (2013) Save our Songbirds. Available from: http://www.songbird-survival.org.uk/save_our_songbirds.html
8- RSPB. (2013) Birds
by name: Sparrowhawk: A top predator. Available from: http://www.rspb.org.uk/wildlife/birdguide/name/s/sparrowhawk/toppredator.aspx
9- Mike Toms. (2008) Return of the Native. Birdtable,
56,7-11. BTO. Available from: http://www.bto.org/sites/default/files/shared_documents/gbw/associated_files/bird-table-56-2008-sparrowhawk-article.pdf
10-RSPB. (2013) Birds
by name: Sparrowhawk: Mortality. Available from: http://www.rspb.org.uk/wildlife/birdguide/name/s/sparrowhawk/mortality.aspx
Impressive blog, full of great information 👌🏻😀
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