• BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

    Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Is this a Goshawk? (1 Viewer)

tconzemi

Tom
Supporter
Europe
There is a huge misunderstanding about size of large females Sprawk and small males Gos. I agree that in the sky 'some males look smaller than female Sparrowhawks' (from Handbook of the Birds of Europe, the Middle East and North Africa and repeated over and over again). Still largest female Sparrowhawks span 70 cm whereas the very smallest male Goshawks span 135 cm, but even more important female Sprawk maximum weight is 342 g (RSPB) whereas the smallest male Gos are heavier than 600 g, so male Gos have allmost double the wingspan and double the weight of female Sprawks, it's just about not being able to appreciate this in the sky. But it takes different size of muscles and wingbeats to keep double the weight in the air, and there flight action as identification pointer comes in. I agrre though that nothing is 100 % sure in this small clip
 

tconzemi

Tom
Supporter
Europe
Doers anyone remember that nice pic posted on BF with 4 Museum specimens Gos Sprawk females and males, can't find it
 

Sangahyando

Well-known member
There is a huge misunderstanding about size of large females Sprawk and small males Gos. I agree that in the sky 'some males look smaller than female Sparrowhawks' (from Handbook of the Birds of Europe, the Middle East and North Africa and repeated over and over again). Still largest female Sparrowhawks span 70 cm whereas the very smallest male Goshawks span 135 cm, but even more important female Sprawk maximum weight is 342 g (RSPB) whereas the smallest male Gos are heavier than 600 g, so male Gos have allmost double the wingspan and double the weight of female Sprawks, it's just about not being able to appreciate this in the sky. But it takes different size of muscles and wingbeats to keep double the weight in the air, and there flight action as identification pointer comes in. I agrre though that nothing is 100 % sure in this small clip
I obviously don't disagree with your overall point, but 135 cm seems like a long wingspan for a "small male" Goshawk. Maybe a typo?
 

Deb Burhinus

Used to be well known! 😎
Europe
I would have thought roughly 10 cm difference?
So just checked Collins
Female Sparrowhawk w/s = 67-80cm
Male Goshawk w/s = 90-105cm

so smallest male Gos about 10 cm longer wingspan than largest female Sparrowhawk.

I honestly think these measurements are next to useless in the field for obvious reasons - Gos to me are clearly bulkier with a broader wing than Sparrowhawk when you see them so actually appear much bigger , I don’t think in terms of centimetres when birding - do any of us?!
 

Biancone

to err is human
Doers anyone remember that nice pic posted on BF with 4 Museum specimens Gos Sprawk females and males, can't find it
I have a clue. Peter Sunesen posted a link on 12.12.2018 in a thread entitled "Is this a sparrowhawk? UK". His post is copied below. That link he gave included size data on nisus/gentilis and an excellent photo of museum specimens that demonstrated clearly the size differential. Unfortunately the link that Peter originally provided seems not to show the photo any more. I downloaded a copy for my own use back in 2018 but I really don't know if it's OK for me to post it again here?

If you scroll down to the bottom post on the Danish forum I link to, there's a link in blue letters, se linket her, which will lead you to another thread which will show a photo of the normal sizes of said two species (adult birds depicted).
A photo that will make a mockery of the oft heard phrase between - perhaps the not so experienced - birders:

"A LARGE female S.H. may be confused with a SMALL male G.H."

This almost makes as little sense as to claim that a large Crow may be quite similar to a small Raven in size.

https://www.fugleognatur.dk/forum/show_message.asp?page=1&MessageID=1960396&ForumID=1

Peter
>>>>>>>>>>>>>
 

Deb Burhinus

Used to be well known! 😎
Europe
A photo that will make a mockery of the oft heard phrase between - perhaps the not so experienced - birders:

"A LARGE female S.H. may be confused with a SMALL male G.H."

I wonder if perhaps the confusion comes from false conditioning? What people seem not to realise, it is not so much the centimetre measurements that matter here. Who can honestly judge accurately a 10 cm difference in wingspan of a bird soaring 300ft above them? - of course not. However, it is the size of the body (exc tail) and broadness of the arm/wing base and hips are where the Goshawk gets it’s real size difference, even, very noticeably, between a male Goshawk and female Sparrowhawk.

People, imo, fall into the trap of thinking there’s little size difference between the latter two because of the field guide method of describing size (ie by wingspan and body length) .Birdwatchers perhaps then, in some small part, fall victim to auto-suggestion in that it is difficult to separate these species in the field. In other words, Field Guides have conditioned people to the idea that body length (inc tail) and wingspan (wing length) are the same as body size (ie bulk of body + tail) and wing size (ie wingspan + breadth). Goshawk -v- Sparrowhawk demonstrate that in the field, clearly this is not the the case. Of course posture/flight behaviour, time of year, even time of day, can impact on size perception of birds in the field, which means studying the bird for as long as possible.

In my own experience, I find that birds soaring on open wings that have a larger body mass, with a proportionately shorter tail, (so similar in length in cm), and broader wings (with a similar wingspan in cm) appear much larger (and are actually much larger in surface area) than other birds that have a similar wingspan and body (inc.tail) length but instead have a combination of a smaller body+longer tail and narrower wings.

Cm size comparisons depend on proximity to be able to assess size difference, the narrower the margins, the nearer the bird has to be for that to be helpful field guidance imo. At 800ft for example, 10cm is largely irrelevant!
 

RafaelMatias

Unknown member
Portugal
I have a clue. Peter Sunesen posted a link on 12.12.2018 in a thread entitled "Is this a sparrowhawk? UK". His post is copied below. That link he gave included size data on nisus/gentilis and an excellent photo of museum specimens that demonstrated clearly the size differential. Unfortunately the link that Peter originally provided seems not to show the photo any more. I downloaded a copy for my own use back in 2018 but I really don't know if it's OK for me to post it again here?


If you scroll down to the bottom post on the Danish forum I link to, there's a link in blue letters, se linket her, which will lead you to another thread which will show a

https://www.fugleognatur.dk/forum/show_message.asp?page=1&MessageID=1960396&ForumID=1

Peter
Direct link to the photo: https://www.fugleognatur.dk/forum/forumpic_showlarge.asp?ID=1769213

And associated (Google translated) text from Casper Stentoft:
Size ratio between Pigeon and Sparrowhawk (Read 1453 times) Posted on 14-08-17 at 21:45​
A recurring question - both here on the site, and among birdwatchers in general - is how the size ratio between Sparrowhawk and Pigeon Hawk actually is.

I recently asked Peter Sunesen about this particular case, and he responded with this photo of the two species from his cold store (Peter is a zoological conservator).

Here is his answer:

Here adult birds, but juveniles have the SAME size, because birds do NOT grow in size (but often in weight) after they have become independent, ie are no longer fed by their parents.

The number is the weight in grams of the people in question, and quite typical Danish individuals, however, the old female is Duehøg from Sweden, and although it is the same breed as in Denmark, northern individuals are a bit larger and heavier.

The bird in question had also completely filled the inn, so the "net weight" would probably have been 200-300 grams less. Danish old females usually weigh 1000-1200 grams (without stomach / inn contents).

Sparrowhawk male 140 g
Sparrowhawk female 277 g
Dove hawk male 898 g
Dove hawk female 1725 g

Sincerely.

Peter​
 

njlarsen

Gallery Moderator
Opus Editor
Supporter
Barbados
A couple of corrections of the google translation: The Dove Hawk is a direct translation of Duehøg = Goshawk. The Inn mentioned a couple of times is the crop.

Another thing to mention is that for the body itself at least, size difference in cm in one direction will result in a weight difference that is the cm difference to the third power.

Niels
 

alexyatespt

Member
United Kingdom
There’s about 40 breeding pairs of Goshawk in the NF and use quite open woodland compared to Sparrowhawk so ironically might be more visible in stronghold areas than Sparrowhawk (Sparrowhawk tend to nest in denser tree stands). Goshawk are very vulnerable to human disturbance (which is high in parts of the NF (and still subject to persecution particularly in Pheasant release areas) which depress population growth. They are also quite sedentary and because they are a colonising species perhaps give the impression there are far more of them overall than there actually are? As for Sparrowhawk populations being impacted, I have not seen any research suggesting it is significant (doesn’t mean it’s not out there so happy to be corrected if anyone has any studies). There's actually some research to suggest Sparrowhawk and Goshawk have a sort of symbiotic relationship with positioning their nests both to maximise breeding of the prey species (for the Goshawk) and maximise protection from other prey species of the Goshawk such as corvids and squirrels. https://www.researchgate.net/public...rowhawk_and_common_buzzard_rivals_or_partners

I’m not sure about the OP video - in some frames it looks a bit Gos-like, in others though it looks too long tailed and slim winged at the bases imo.
View attachment 1363680 View attachment 1363681
Thanks for the very interesting paper on spatial relationships!
 

Deb Burhinus

Used to be well known! 😎
Europe
Thanks for posting the video and giving us the opportunity for discussion, Alex!

And welcome again to Birdforum 🙂
 

Biancone

to err is human
Yes, thanks for posting! Just wanted to add that the vital link that Rafael posted above (#28) still doesn't work on my desktop browser (Firefox) but does in Safari on my ipad. Curious. But the image is certainly worth viewing...
 

RafaelMatias

Unknown member
Portugal
Yes, thanks for posting! Just wanted to add that the vital link that Rafael posted above (#28) still doesn't work on my desktop browser (Firefox) but does in Safari on my ipad. Curious. But the image is certainly worth viewing...
The credit on that image goes all to you, I would have not posted it if you haven't find it first (y):)
 

Andy Adcock

Well-known member
England
I wonder if perhaps the confusion comes from false conditioning? What people seem not to realise, it is not so much the centimetre measurements that matter here. Who can honestly judge accurately a 10 cm difference in wingspan of a bird soaring 300ft above them? - of course not. However, it is the size of the body (exc tail) and broadness of the arm/wing base and hips are where the Goshawk gets it’s real size difference, even, very noticeably, between a male Goshawk and female Sparrowhawk.

People, imo, fall into the trap of thinking there’s little size difference between the latter two because of the field guide method of describing size (ie by wingspan and body length) .Birdwatchers perhaps then, in some small part, fall victim to auto-suggestion in that it is difficult to separate these species in the field. In other words, Field Guides have conditioned people to the idea that body length (inc tail) and wingspan (wing length) are the same as body size (ie bulk of body + tail) and wing size (ie wingspan + breadth). Goshawk -v- Sparrowhawk demonstrate that in the field, clearly this is not the the case. Of course posture/flight behaviour, time of year, even time of day, can impact on size perception of birds in the field, which means studying the bird for as long as possible.

In my own experience, I find that birds soaring on open wings that have a larger body mass, with a proportionately shorter tail, (so similar in length in cm), and broader wings (with a similar wingspan in cm) appear much larger (and are actually much larger in surface area) than other birds that have a similar wingspan and body (inc.tail) length but instead have a combination of a smaller body+longer tail and narrower wings.

Cm size comparisons depend on proximity to be able to assess size difference, the narrower the margins, the nearer the bird has to be for that to be helpful field guidance imo. At 800ft for example, 10cm is largely irrelevant!
Agree totally with this and I still think that the bird does not appear to have the bulk of a Gos.
 

Users who are viewing this thread

Top