Comparing Collared Sparrowhawk and Brown Goshawk
Brown Goshawks and Collared Sparrowhawks can be difficult to distinguish in the field. When studying the literature and the web, one finds a number of features, which are supposed to help identifying the correct species. Below is a summary of the features, which I have found commonly mentioned in regard to the identification of these raptors. I have selected images from my collection of more then 10 years of bird photography in Australia and added some remarks in an attempt to check and comment on these features.
Tail shape
Brown Goshawks are supposed to show a rounded tail, whereas the tail is supposed to be square (or even slightly notched) for Collared Sparrowhawks. This impression is created by the fact that the tail feathers are of equal length in Sparrowhawks as opposed to be of varying length in Goshawks (Example 1 and Example 3).My impression is that the "rounded tail"-feature is more pronounced in the female than in the male birds. Example 6 shows two birds in flight, which allows us also to check on the tail shape. You will find that things are again less clear than one would hope.
So, generally I think the tail shape is a feature, which is important but needs to be used in the field with caution, preferably in combination with other field marks. Unfortunately, all what we will usually get from a distant bird flying by is a brief look at the tail shape ... in such a case one then needs to look at the way the birds fly and see if there is something for the ID process to draw from that.
From the CornellLab Birds of the World: ... in flight [a Goshawk] ... glides on slightly bowed wings and soars on slightly bowed to slightly raised wings. Flight action is quick, with bursts of deep flaps. The Collared Sparrowhawk appears slightly more compact, [and has] ... a lighter flight style. I will need to get some video footage in the future to check on this :-).
Brow
Very often Brown Goshawks are described as having more defined brow ridges, resulting in a glaring look while the Collared Sparrowhawk appears to stare. Now, not being a native English speaker, I have looked up the definition of staring and glaring. The Merriam-Webster Dictionary says:
- staring: to look fixedly often with wide-open eyes
- glaring: having a fixed look of hostility, fierceness, or anger
Which sounds, well, kind of right although not very precise and the two meanings sound still a bit fuzzy to me (Example 4). Describing Sparrowhawks as the finer set birds, and having a smaller head would be more useful in my eyes.
(Example 5) demonstrates additionally how lighting can change the impression one gets in the field of the brow.
Legs and middle toe
Most authors mention, that Sparrowhawks have a much longer middle toe and finer legs (Example 3 and Example 4). We just rely on the fact that the birds show their feet well. Inspecting Example 1 again, one finds that in this case the Sparrowhawks were cooperative, the Brown Goshawks were not.
Cere
The cere is the area between the upper bill and forehead feathers. Collared Sparrowhawks are said to have some pale-blue in front of the cere, for Brown Goshawks it is supposed to be yellow, leading directly into the black bill (Example 2).
Wing shape
Brown Goshawks are said to have "less curvaceous wings" when compared to Sparrowhawks as the CornellLab Birds of the World calls it (Example 6)
Generally said, identifying difficult birds from a fleeting view or a single photo can be difficult for similar species. Without multiple views a lot of the relevant information may be missing, and in a single view the lighting can create great confusion due to changing colors and giving false impressions or overly emphasizing certain features. So, there is often plenty of room for doubt despite how certain we are about a single feature. I'd like to add that I am far from being a reference expert but I have enjoyed working with these images almost as much as I have taking them; it was a worthwhile learning experience!
Cheers!
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The TTG Backlight web tools, which I use for the production of my own website, allow me to compare two photos in an elegant way by swiping a slider to transition from one shot to another. I have used this function here to show photos from Collared Sparrowhawks (left photos) and Brown Goshawks (right photos). So, grab the slider and have a look yourself.
Example 1 (TAIL SHAPE). These images show a pair of Collared Sparrowhawks (shot at the Warrumbungle NP) and a pair of Brown Goshawks (photographed in FNQ on our way back from Iron Range). The two female birds (the bigger individuals) show the tail shape feature well, but it is already less clear for the male birds. For both species the tails of the male birds are slenderer, and the described effect is not obvious.
Example 2 (CERE). These images demonstrate this feature well. It is a very useful criteria, I think, when inspecting a good quality image. I doubt though it'll be helpful in the field looking through a pair of binoculars.
Example 3 (LEGS and MIDDLE TOE). Here differences in the length of the middle-toe are obvious. When checking the TAIL SHAPE feature in this image, then the different lengths of the tail feathers are clearly visible for the Goshawk, but just imagine, the bird would show you its back, then you would see a notched tail, because the shorter inner feathers would not be visible at all.
Goshawk / Sparrowhawk-4
Example 5 (BROW) shows the same bird (Sparrowhawk), only having turned its head. In the left case the shadow above the eye is creating the illusion of a rather strong eyebrow, whereas this impression does not arise from the right image, where the bird has just turned its head so that it is fully sun-lit.
Example 6 (TAIL SHAPE) shows two birds in flight. One would expect that at least here the rounded/square tail feature should work but when, like in this case, the Goshawk is a moulting immature bird, and the Sparrowhawk a mature male, then one can easily come to a different conclusion, especially when observing the birds from a longer distance! When looking at Example 6 regarding the (WING SHAPE) then the curvature of the front wing lines are just marginally different and will be difficult to distinguish in the field. Although I must admit I have seen images of Brown Goshawks supporting that this species can have a straighter leading edge of the wing. So, observing a straight front wing line of a bird in flight can be an indicator of seeing a Brown Goshawk, it being more curved does in my opinion not indicate we look at a Sparrowhawk. Differences could possibly be related to the age and sex of the seen bird.
