Sparrowhawks - how frequently do they need to make a kill?

[luckyoldme]

Just very occasionally I get Sparrowhawk attacks in my suburban garden in Reading - have seen one female and one male at different times of the year, so not sure they are a pair. I'm curious to know how often a Sparrowhawk has to make a kill to survive? If it was one kill per day per individual, that's 365 birds per adult per annum and with a youngster to feed in breeding season even more, which seems like a huge number over the course of a year, particularly in my area where I don't see a particularly high head count of potential prey birds (generally very small flocks of finches, tits, doves and sparrows). Does one pair in an urban area typically need a very large territory to survive?

[FUDGEY]

I read that it was two small birds a day required to survive, but the Female at my feeding station is catching at least 4 per day now and that is all I see so dont know if she is catching more elsewhere, but I guess She will be. Last week she caught 2 Coal Tits and a Chaffinch in 40 minutes! I know a guy that studies them closely and his Male has been seen catching 12 birds a day when feeding young. The size of territory will be prey dependant so dont worry it wont wipe the small birds out. Cats will kill millions of more birds each year than Sparrowhawks so if you want to worry about anything predating your birds its these.

[bobbarber]

Originally Posted by FUDGEY

The size of territory will be prey dependant so dont worry it wont wipe the small birds out. Cats will kill millions of more birds each year than Sparrowhawks so if you want to worry about anything predating your birds its these.

So very true Fudgey, but I wonder how long it will take to get this fact across to the general public...Bob

[RoyW]

Originally Posted by FUDGEY

I read that it was two small birds a day required to survive

I believe that two small birds, or one larger bird, is considered to be a typical amount taken - but they can survive on less if they have days when hunting is poor (even going a few days without food - with females better suited to surviving without food due to their larger reserves).

Originally Posted by FUDGEY

but the Female at my feeding station is catching at least 4 per day now and that is all I see so dont know if she is catching more elsewhere, but I guess She will be. Last week she caught 2 Coal Tits and a Chaffinch in 40 minutes!

Is there some thing distinctive about this female? I would suspect that more than one female is involved here unless you can be 100% certain that there is only one.

Originally Posted by FUDGEY

I know a guy that studies them closely and his Male has been seen catching 12 birds a day when feeding young. The size of territory will be prey dependant so dont worry it wont wipe the small birds out. Cats will kill millions of more birds each year than Sparrowhawks so if you want to worry about anything predating your birds its these.

Sparrowhawks breeding is timed to coincide with the fledging of tits and other birds, so there is plenty of easily caught food available when they most need it. Individual Sparrowhawks will kill more birds than individual cats, but cats kill far more overall because there are many times the number of cats as Sparrowhawks - and cat numbers aren't limited by the availability of prey.

The numbers of small birds that can potentially be prey for Sparrowhawks are also much, much higher than most people realise (even though many species are declining).

[Dogghound]

10-12 birds per day is around average during the breeding season when they are feeding the nestlings. So theoretically they usually catch about 1 prey item every couple of hours although in reality prey capture peaks and troughs through the day due to activity levels (i.e. more prey is captured during the morning). Usually sparrowhawks have a very low impact on prey species populations and in most cases only take about 5% of the population in a given area through the breeding season and even less outside of the breeding season. Sometimes they can put increased pressure on a species but this is usually due that species either being vulnerable or occurring in lower densities due to other factors. Sparrowhawk impact on prey numbers has been widely studied. The species is well suited to this due to its populations increasing into areas when it was previously not found enabling before and after data to be recorded.

It must also be noted that they have quite a low success rate with about 1 in 10-12 hunts being successful. A predator like a sparrowhawk picks up old weak (and young) birds this is largely benificial to the population as it increases fitness levels in the population. Even with young birds I personally find you get alert ones and ones which seem oblivious to danger, not a trait which would be benificial if passed down to other generations.

[Acipiter]

[quote=RoyW;862498]I believe that two small birds, or one larger bird, is considered to be a typical amount taken - but they can survive on less if they have days when hunting is poor (even going a few days without food - with females better suited to surviving without food due to their larger reserves).




I agree with you Roy, I was watching a female with a wood pigeon the other day I have a pic of the remains. Just about it all, I was thinking about posting the pic, but I thought it might be too grizzly to show. There was just a small peace of sternum and leg left.

[FUDGEY]

Very interesting as usual. Roy deffo the same 1st Winter Female, she is a very clever bird adopting the same tactics several hours a day. I have a large water feature on stilts about 10ft x 7ft and she just saunters in and lands on a log under the table. After 10 minutes or so the birds come back and she makes her attack. If she misses she just goes back under the table and waits. Some times this can go on and on for hours until she catches. The other day though she was on the ball and caught every time. You can see is the rubbish video the table I mean and a lucky Coal Tit.

23rd December 2011 Sparrowhawk | Flickr - Photo Sharing!

[FUDGEY]

Heres a clip I just found from two days before. You can see her here under the table.

21st December 2011 Sparrowhawk strike | Flickr - Photo Sharing!

[RoyW]

Originally Posted by FUDGEY

Roy deffo the same 1st Winter Female, she is a very clever bird adopting the same tactics several hours a day. I have a large water feature on stilts about 10ft x 7ft and she just saunters in and lands on a log under the table. After 10 minutes or so the birds come back and she makes her attack. If she misses she just goes back under the table and waits. Some times this can go on and on for hours until she catches. The other day though she was on the ball and caught every time. You can see is the rubbish video the table I mean and a lucky Coal Tit.

23rd December 2011 Sparrowhawk | Flickr - Photo Sharing!

Thanks for that interesting information. It would seem unlikely that two different 1st winter females would be behaving in exactly the same way, using such a specific hunting method and waiting in the same spot - but personally I would want to see some sort of specific identifying mark that identified the individual before I would be prepared to say that it definitely was just one individual. If there are few ideal spots for a Sparrowhawk to wait near where birds frequently gather it is possible that two individuals might use the same perch (up to three Sparrowhawks, of different sexes/ages, regularly used to attack a Starling roost near me, and all three would use the same branches on a dead tree at different times).
If we assume that it is the same female I would wonder if it is sometimes caching prey so that it can come back for it on days when hunting is more difficult.

[Acipiter]

One crafty hawk there, and Very clever. It looks like more whatching on the cards for you Alan Lets us know the outcome Please.