Talkback: Sparrowhawk overhead - Page 3

My sparrowhawks are dessimating my bluetit population at Sycharth in North Wales! Ive managed to one with my Nikon. http://sycharthbandb.wordpress.com/2010/02/05/sparrowhawk/

i want facts

not stories

Hi Mini,let me give you some facts, a survey held by prof,Ian Newton between 1988 and 1991 showed 34.500 pairs of sparrowhawks,for each pair there is a single bird,so approx 90.000 sparrowhawks,Fact, each bird needs 2.5 to 3 small birds per day to survive. Fact,that is 270.000 song birds a day between 82 and 98 million songbirds a year. THAT IS FACT! and spare a thought this survey was carried out 20 years ago,what with enjoying total protection from well meaning dogooders their numbers have probably doubled,while sparrow numbers have fallen by 65%. the R.S.P.B.would have you believe it's down to farming methods,but there,s not much farming going on in London,Leeds,Manchester,need i carry on.

Whilst sympathising with Mike & Pete about their pigeons, the points about songbirds & effects on their numbers are a bit surreal. If a population (of songbirds, say) is stable over time, then predation "has no effect on their numbers". Another way of saying this is that small songbirds produce one, two or even three clutches of eggs through a summer because that's what is required to sustain the population. So, if two adults have produced fifteen chicks by the end of the summer, perhaps one of the adults and one of the chicks will have survived to breed with others of their species by the following spring - ie two birds, as there were last year. This natural balance works well, as otherwise after a few years we'd be knee-deep in prolifically breeding songbirds (irony). Moving on; if prey levels fall, eg sparrow numbers, then predator numbers will also fall. However, if the numbers of sparrowhawk and of other sparrowhawk prey-species (tits, thrushes etc) remain broadly constant, then the reason for the decline in sparrows is unlikely to be because Mike & Pete aren't allowed to shoot sparrowhawks.

Lovely blog, Richard. I like sparrowhawks, and enjoy seeing them in my garden. I just hate it when they eat baby chicks. Why can't they just live off street pigeons all year round?