Friday, 1 October 2010

How many marsh harriers stay all year round?

Marsh Harrier over crop circle, Wadi Maknusah, late March. Photo by eclipsomanics  

It's been known for a long time that central and northern European marsh harriers migrate on a broad front to and from sub Saharan Africa. This is reflected in the distribution maps of guides such as the Collins Bird Guide (which I take everywhere).

Actually the migration is not uniform across the whole front. In spring 200 birds use the Straits of Gibraltar but 1000-1300 birds have been counted crossing Sicily to mainland Italy and very few over Istanbul.

Route of migrating Tunisian and Libyan marsh harriers in spring

The birds using Sicily come from Tunisia and Libya. So its fair to say that Tunisia and Libya are very important in marsh harrier migration. If you want more information, there is an excellent review of the migration paths and numbers by Nicholantonio Agostininin Ardeola 48(1) 2001,71-73 . 

Having established that Libya is a big factor in marsh harrier migration is not the end of the story. The UN winter water counts in Libya always pick up a few records of marsh harrier in several wetlands. The bird is now a confirmed wintering bird too.

But that's not the end!  I observed a family of marsh harrier all summer at the "super farm" at Jardinah south of Benghazi. Jardinah is one of about 15-200 super farms with their state-of-the-art irrigation which are scattered throughout the country especially in desert or semi-desert areas. 

I have wondered where else marsh harriers might be. Then I saw the picture (at the top) of this blog by eliptomaniacs. It was taken in another super farm, this time in the south of the country.

It was taken in late March at precisely the time when most marsh harriers cross from Sicily to mainland Italy. If it had been taken one or two weeks later it would have been proof that this bird stays the summer.

My best guess is that most of the super farms have a resident family of marsh harrier. It would make a good research project to find out. So if there are any researchers out there please consider it. I would do it myself but I have to keep reminding myself that I have a full time job and it isn't bird watching.

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