Question: Which has the longer middle toe – Brown Goshawk or Collared Sparrowhawk?
Common folk law would seem to suggest “Collared Sparrowhawk” as has often been claimed on this forum.
The text in the “Similar species” and “Recognition” sections for Brown Goshawk in HANZAB would seem to suggest “Collared Sparrowhawk”.
The text for both species in “The Birds of Prey of Australia” (Stephen Debus, 1998) would seem to suggest “Collared Sparrowhawk”.
but……..
The measurements in the respective species entries in HANZAB would seem to suggest “Brown Goshawk”. That would seem reasonable considering that the Brown Goshawk is the bigger bird (male to male; female to female).
However, there is one aspect to the toe measurements in HANZAB which I find interesting and could help to explain this anomaly. The toe measurements for Collared Sparrowhawk are stated to have been “taken without claw” whereas there is no such qualification noted in respect to the toe measurements for Brown Goshawk. Is it possible that different methods were used for measuring the middle toes of the two different species? Surely not?!
Bob Inglis Sandstone Point Queensland Australia
Sent from my no-name desktop PC. ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
I wasn’t going to pursue this topic any further as it seemed there was little interest, however, Peter Shute has encouraged me to go a bit further after all. For those birders interested I will spend some time over this weekend (raining in SE Queensland) to work on some digital images which should help observers to understand the concept of the distal joint of the middle toe and its relationship with the base of the claw of the outer toe. I only have limited images of one species (not 100% sure which species, though) which should be good enough to illustrate the concept. When the images are ready I will upload them to a web-page and I will advise when they are ready for viewing.
Bob Inglis Sandstone Point Qld Australia
This email powered by “Grey”.
In response to the request for toe photos, here is a sparrowhawk: < http://www.birdforum.net/gallery/showphoto.php?photo=198100 >. (If need be, click the red “Join for free” button.) Imagine the outer toe swung round to lie beside the middle one.
The distal joint is the articulation between (a) the toe bone at the end of the middle toe, in other words the section of the toe that bears the claw, and (b) the bone “before” it, i.e. the next bone towards the body. So, in the photo you are looking for the outermost two yellow segments of the middle toe, and then homing in on the angle between them.
I hope this makes sense. Sorry no goshawk. I took this shot at Gluepot, and a goshawk came down the previous day, when I was counting birds and the camera was in the car.
John Seymour ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================
“Also from HANZAB: For Collared Sparrowhawk: distal joint of middle toe lies beyond base of outer claw… . . . For Brown Goshawk: distal joint of middle toe is level with or shorter than base of outer claw.”
Has anyone got any photos that clearly illustrate the above? And can “distal joint” be taken to mean the base of the claw, or can the actual joint position be distinguished in photos?
Peter Shute
My point in starting this thread was to encourage people to avoid trying to use the absolute length of the middle toe of these two species or the relative lengths of the middle toes of the two species as an identification point to determine which species is being observed. The absolute lengths and the relative lengths are irrelevant irrespective of whether the same method or not was used to obtain the measurements used to compile the tables in HANZAB. Both species have elongated middle toes. There is considerable overlap in the lengths of the middle toes of the two species. It is very difficult to determine the length of the middle toe when it is wrapped around a tree branch. Even high quality digital images don’t make that any easier.
Instead of comparing the middle toe lengths of the two species for identification the toes should be used in the following manner: the outer toe; base of the claw of the outer toe.
The following percentages are taken from HANZAB: For Brown Goshawk: outer toe c. 70% of length of middle toe; For Collared Sparrowhawk: outer toe c. 63 – 67% of length of middle toe.
OK. When you have worked out how to accurately measure that in the field let me know.
Also from HANZAB: For Collared Sparrowhawk: distal joint of middle toe lies beyond base of outer claw. (That is probably what makes the middle toe of that species look particularly long but it could just mean that the outer toe is relatively short compared to the middle toe.) For Brown Goshawk: distal joint of middle toe is level with or shorter than base of outer claw. (Perhaps the outer toe on this species is relatively short.)
Once again, that could be hard to judge other than with the bird in the hand, however, it is possible to see this in high quality digital images of birds flying directly overhead.
Personally I would forget about using toe lengths as identification points but would rather concentrate on the appearance of the bird/s. I am sure it would be possible to eventually become proficient in evaluating the appearance of the legs/feet (thick or thin, stout or slim) if one was to observe enough examples of each species. Or if one was to take enough photos of the two species of the quality of Chris Ross’s two superb images.
Bob Inglis Sandstone Point Qld
No Wi-Fi used in sending this email.
Hi Peter,
Yes I believe it refers to relative length compared to the other toes on the foot, not between species. Also in my experience Collared Sparrowhawks have more slender toes.
Cheers, Chris
Sent from my iPhone
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================
I thought the important thing was the relative length of the middle and outer toes. I think someone mentioned “length” in this thread without using the word “relative”, but I assumed that’s what they meant. Is absolute length important?
Peter Shute
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================