Wednesday, 6 September 2017

Bird ID Correction from 01 March 2017

Brown Goshawk v Collared Sparrowhawk

At our visit to Macalister Wetlands back in March, we [probably, me/I] called an overflying raptor a female, juvenile Brown Goshawk. See the blog here. Whilst "cleaning up" my bird images on the computer today, I looked again and decided I may not have been correct. I put the image onto the FaceBook Australian Bird Identification page and Luke Flesher and Angus Daly confirmed my thoughts.

Critical aspects of this bird are:

There is no evidence of moulting [shorter feathers growing out] interfering with the features of identification.

Tail feathers
The difference between the two species is in the length and shape. CS have shorter inner retrices so the tail should appear "squared off" and generally have a central notch. This is the case here. The tail is not rounded and you can just see a small notch. BG have outer retrices which are progressively shorter giving BG tail a rounded appearance.

Tail Length cf Leg Length
The BG has a long tail and, when viewed from below, there is a lot of tail uncovered by legs. The CS has a relatively shorter tail and, as above, the legs take up a bigger proportion of the tail length.

Toe length
The middle toe of the CS is much longer than the BG relative to the other toes on the foot. The legs are also quite slender compared to BG. BG legs look like they couldn't break but CS legs look like a decent bang would break them!

These wings are quite wide. The Australian Bird Guide for CS says, "Secondaries bulge beyond the rest of the trailing edge of the wing". This is what we see here.

The smallest bird is a male CS [30cm]. Next biggest is a female CS[40cm]. Only slightly bigger is a male BG [40cm] and the biggest is a female BG [50cm].

Both Morcombe and Pizzey quote the same figures. When a single bird flies over with no reference to anything else [where was the harassing magpie you may well ask?], it is very hard to judge size. On the day I recall John and I both thought it was a "large" bird, larger than a CS would be. But I was wrong. Just goes to show how challenging our hobby can be.

Juvenile, probably male, Collared Sparrowhawk.

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