A question about wingspans (2 Viewers)

[Gonçalo Elias]

Hi all,

While I was gathering information about bird wingspans, especially waders, I came across very significant discrepancies in the wingspan values of the birds presented by various sources.

I've noticed this in plovers, but I've now found that the problem affects many other species from different families.

Let me take the case of the Common Ringed Plover Charadrius hiaticula as an example.

According to the Collins Bird Guide (1st edition), this species has a wingspan of 35-41 cm.

However, when I looked up the website birdsoftheworld.org, I found a value of 48-57 cm (which seems quite high for this species) and shortly afterwards I noticed that the other plovers are also given large values. I'm not sure what the correct value is, but this huge discrepancy between different sources doesn't make sense. One of the values must be wrong.

I then tried to confirm the values in other sources, and when I opened the BWP (CD-ROM version) I found this (see image below).

As you can see, BWP also has the 48-57 cm value. The information presented on birdsoftheworld.org for European birds was imported from HBW, so the fact that this number from 48-57 appears in BWP also leads me to believe that HBW may have used the values from the BWP that later migrated to birdsoftheworld.

Right now my problem is this: how do I know which values are correct? What is the best source for wingspan values?

I would appreciate any ideas about how to deal with this.

Best regards,
Gonçalo
Portugal

 

[Welsh Peregrine]

The maximum values will be for fully stretched wings, which would rarely if ever be actually produced by a living bird in the field, but which can be measured reliably by a ringer or on a museum specimen. There are probably protocols for taking other measurements, but I don’t know what they are; some books may describe them (Shorebirds has a diagram, but I have not got it to hand at present)

 

[Gonçalo Elias]

The maximum values will be for fully stretched wings, which would rarely if ever be actually produced by a living bird in the field, but which can be measured reliably by a ringer or on a museum specimen. There are probably protocols for taking other measurements, but I don’t know what they are; some books may describe them (Shorebirds has a diagram, but I have not got it to hand at present)

Indeed, however in the introduction of Collins Bird Guide (which has the smaller values) I found this explanation:

The wingspans are intended to indicate the greatest possible extent that a bird can reach during flight (slightly higher values may be reached if, in a live bird, the primaries are pulled, fully stretching the wings, but artificial measurements of this type were avoided). In the current bibliography, there are many misleading measurements. Those presented in this guide are based for the most part on original measurements taken on live birds, supplemented with measurements taken on skins and photographs.

From all the available information it seems to me that:

• the measurements presented by BWP are old (about 40 years old in the case of waders)
• those values have been used and quoted by other sources, probably without any sort of verification
• it is not clear to me how the measurements of BWP were obtained, and whether they relate to live birds or skins, however the measurements 48-57 cm are shown in the section "Field characters"
• Collins Bird Guide states that they made original measurements, including on skins, and claims that values published elsewhere are often wrong

I would like to know if there are any additional sources for this kind of information.

 

[Welsh Peregrine]

Within BWP it usually quotes sources such as number of specimens measured and location of specimens measured if from museum collections.

 

[Gonçalo Elias]

Within BWP it usually quotes sources such as number of specimens measured and location of specimens measured if from museum collections.

Yes, it does, in the section 'measurements'. But that section usually comprises data on wing lenghts, bill and tarsus - not wingspans.

 

[Welsh Peregrine]

What about BTO ringers guide to non-passerines? Might be an alternative source of information.

 

[Brian J Small]

BTO give a wingspan of 52cm - BTO BirdFacts | Ringed Plover

But in the same page an average wing length of 135.3mm. By using the photo in the link below, we can see a wingspan of a Ringed Plover is just over 3 times the wing length (say 3.2x). Multiply 135.2mm by 3.2 and you certainly don't get 52cm!

43.2cm I make it, which fits in nicely with neither (Svensson in) Collins nor BWP/BotW... I find it hard to believe a Ringed Plover has a wingspan of over half a metre.

Ringed Plover by Heiko Peters

Visit our new-look Galleries to view and search images of thousands of bird species, and join our worldwide community of bird photographers

www.birdguides.com

Brian

 

[Gonçalo Elias]

Brian, thanks. Exactly what I thought: half a metre is too much.

 

[Gonçalo Elias]

The website birdspot also mentiones 48-58 cm wingspan for the Ringed Plover.

I'll try to find out what source they used.

 

[Gonçalo Elias]

I got a reply from birdspot, they said the values on their website come from the RSPB.

Indeed the RSPB website mentions a wingspan value of 48-57 cm for the Ringed Plover:

Ringed Plover Facts | Charadrius Hiaticula

A dumpy, short-legged wading bird. Brownish grey above & whitish below, an orange, black tipped bill, orange legs, a black-white pattern on its head & breast

www.rspb.org.uk

 

[Gonçalo Elias]

I wrote to the RSPB about this and got the following reply:

Thank you for your email and for taking the time to bring this to our attention.
I can confirm that I have passed on your feedback to our internal team for them to look into. The ringed plover webpage measurements were originally compiled by our conservation science team. We are currently looking into reviewing the information on our A-Z bird webpages, including our ringed plover webpage.
Many thanks again for getting in touch and sharing your feedback with us.

Let's see what happens next.

 

[dantheman]

Let's see what happens next.

The best (or worst) may be this, where they seem to have hedged their bets and combined the two, giving a wingspan of from 35 to 57cm! (An example from googling)

Ringed plover

The ringed plover tempts underground prey to the surface by 'foot-trembling' i.e., tapping its feet on the ground to mimic raindrops.

scottishwildlifetrust.org.uk

Good luck in your quest ...

 

[Gonçalo Elias]

Back to this subject... I got a reply a few days later but forgot to mention it here.

It reads:

Hola Gonçalo
Thank you for your email. The wingspans come from Birds of Western Palaearctic (specifically the concise version), so I think it must be that the definition of wingspan differs. For BWP I think it may be wingtip to wingtip with the wings held straight, whereas I guess for the bird guide it is more how the bird is holding them in flight, that is a bit folded?