Sparrowhawks, polygynous breeding

[FUDGEY]

Has any one ever heard of this? I got told about it yesterady and at first didnt believe it. There was one nest that the 2 Females and the Male fed the offspring. I cant get my head round it. How unusual is this and does it occur with many other species?

[A Rural Heart]

Hi Fudgey,

I have always known that birds can be polygynous. If you type in this;

Factors promoting polygyny in European birds of prey—a hypothesis

Then download the PDF file it mentions Sparrow Hawks and other birds of prey stating that the rodent eating birds are more prone to polygyny than the bird eating ones which suggests its perhaps a rarer trait in Sparrow Hawks?

Kind Regards,

Lee.

[Dogghound]

It is recorded in most birds although more common in some species than others. With sprawks you often either get a male which helps rear two different nests or more usually (if you can say that) both females lay in the same nest and one usually remains with the male to rear, its not unheard of for the second female to help feed the clutch especially when the young are older or when they have just fledged.

Another hypothesis is that one of the females mates has died around pair formation leading to confusion, in which the male finds a lone female within breeding condition and instinctively starts to display.

Certainly recorded in barn owl, tawny owl, kestrel etc too, although something I have yet to come across in the field.

[Hobjob]

Marsh Harriers do it too - but they have two nests I blieve. Does that exclude the term polygany?

[Acipiter]

Hi Alan, I have read about two females laying in one nest before, but I have never once found this myself, in spite of the many years iv'e been studying them. How ever I do have experience of one male with two females. This is a rough account of what normally happens from "my experiences". The male builds two nests, nothing unusual about that since this can happen, When I spot two hens on the scene my nose begins to twitch. All seems to be ok fore awhile the male feeding the two females. After a few days one of the female will be spotted off the nest calling for the male, one or two more days later this female will give up and desert. This is because the male has simply stopped feeding her. I have observed this same pattern repeated with a few pairs that I have been studying over the years. It has always ended this same way.