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Old Thursday 28th June 2012, 08:37   #1
blueshortwing
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Laying dates

I am looking at the variation of laying dates, between different pairs of sparrow hawks within the same habitat in the same year. And trying to work out the reasons why they should differ. Apart from the age of the birds concerned, how rich the habitat maybe, or how good a hunter the male maybe as a provider. Could variations in the genetics within individual birds play apart, or indeed anything else I may have missed.

Thanks. George.


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Old Thursday 28th June 2012, 09:48   #2
Pugs1
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Weather, choice of nest site, experience, intra specific competition for best nest sites (young\less established birds pushed out to less suitable sites), established occupation of optimised areas and so forth.

Genetics is an idea but how would one prove that, unless of course it was accepted that the weaker (weaker genetics?) had the less suitable territories\breeding area but that would be hard to prove.

With the Barn Owls I studied, there wasn't much variation in laying dates between pairs and most pairs studied had between 500m - 1 km distance (optimal habitat) from one another's nest site. Indeed the factor always seemed to be weather patterns and the abundance of prey.

Might be worth plotting the sites and then checking each territory suitability, could disturbance be a factor, is there any other predator\competitor within an individual pairs breeding range and so forth

Last edited by Pugs1 : Thursday 28th June 2012 at 10:10.
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Old Thursday 28th June 2012, 10:35   #3
blueshortwing
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Laying dates

I have ruled out the weather as I already stated it all took place in the same year in the same place. Apologies if I didn't make it clear enough. There is know difference in nests sites as well, as all were perfectly good. All the birds have been here for around the same number of years. (They are the same birds) The nest sites were all were perfectly good as well. I could be wrong but having observed these pairs for some years, I think "one of the main reason" is food related. Thank you for your thoughts anyway.
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Old Thursday 28th June 2012, 10:41   #4
Pugs1
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Aye, well as stated prey (type of prey variations between pairs, abundance in individuals home range etc) usually is a big factor. With regards to the individual nest sites, what I'm getting at is there an external influence on the sites which vary on laying dates, could there be an Owl species nesting close by, as an example?
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Old Thursday 28th June 2012, 10:54   #5
blueshortwing
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Laying dates

They are all bringing in the same prey species Pugs 1, and there are no owls nesting within 3 miles of my sparrow hawks, or other raptors for that matter.
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Old Thursday 28th June 2012, 11:17   #6
blueshortwing
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Laying dates

Hi pugs 1, I have made my self a cup of tea and gone through your posts again. and thought through what I all ready know. When I said food related I meant to say I have a "strong feeling" it could be down to the fact that some of the males are far better at hunting then others.

George.
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