Tuesday, November 22, 2011

Northern Harriers

Seen as I'm on reading week from Uni, thought I best do some reading/research!


This got me thinking about the 2w male Northern Harrier that was kicking around Tacumshin not long ago and how at first glance it could be dismissed as a 2w Male Hen Harrier. 

Searching through Surfbirds I quickly found photos of the Doncaster 2w male Hen Harrier taken by Ron Marshall who has kindly granted me permission to reproduce his images here. 

                                                                    © copyright Ron Marshall

As you can see obviously a non-adult male harrier, but why is it cyaneus and not hudsonius? By comparing photos of the Doncaster bird and male Northern Harriers from the US, I'll try to highlight the differences with the help of some brilliant images courtesy of Bob Steele http://www.bobsteelephoto.com/home/home.html

Doncaster bird © copyright Ron Marshall

Male Northern Harrier © copyright Bob Steele

Comparing these two photos the two birds look fairly similar, darker headed appearance and brown flank barring. However further photos show;

                                                          Doncaster bird © copyright Ron Marshall

                                                    Male Northern Harrier © copyright Bob Steele

These two photos show the extent of black on the underside of the primaries and how it varies from one (sub?) species to another, with cyaneus showing extensive black reaching a lot closer to the underwing primary coverts. The line of black could be described and being parralel with the wing base on cyaneus and diagonally away from the wing base on hudsonius.

                                                             Doncaster bird © copyright Ron Marshall

Male Northern Harrier © copyright Bob Steele

These two photos show how the Doncaster bird has dark tips to the upperwing coverts similar to adult male hudonius, however note the black patterning on the top side of the primaries. In cyaneus the primaries are black through to p5 whereas hudsonius only to p6 (with only a small black tip on p5). Also note the extent of the black, in cyaneus it extends right up to the upper primary coverts but in hudonius it only reaches it in p10 showing grey bases to the primaries from p9 onwards.

Male Northern Harrier © copyright Bob Steele

As can be seen in the above photo ad male hudsonius show barring on the tail feathers, ad male cyaneus do not show this, however 2w male cyaneus do which can be seen on the Doncaster bird here although this is a lot more faint than hudsonius

(So would that make this cyaneus a 3cy due to the barred retained outer-tail feathers?)

So although it seems the Doncaster bird is indeed a 2w cyaneus, how many ad male hudonius have been overlooked as 2w male cyaneus?! Hopefully not too many!

I've never been lucky enough to see a hudsonius, so info here taken from various books and internet searches! 

Many thanks to Bob Steele and Ron Marshall for allowing me to use their photos on this post.

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