Unusual black-headed gull, Ireland (North East coast) (2 Viewers)

[leifvester]

Hey,

I saw this gull today. Quite sure it's a black-headed gull, but it had a few variations that made it stand out to me.

1. Small and straight dagger bill (not curved downward)
2. Very little black on the bill
3. Quite a clean head with a soft grey ear covert (usually a dark spot)
4. Rose-tinted breast
5. Small and very round head

I've included some comparison photos as well.
Is there any particular reason it is like this? Appears to be an adult bird. Is it diet or the sex of the bird?

 

[leifvester]

I've got some flight photos.

The wing tips look grand for Black-headed gull, but it also looks small in flight, and the underwing dark - just the lighting / within normal range?

It gives me Little Gull vibes, but probably just a Little Black-headed gull?

Edit: It also appears to have short wings, which adds to the Little gull feel.

 

[dwatsonbirder]

On first glance, this almost looked like a candidate Bonaparte's gull, but closer inspection reveals a red base to the bill, a lack of grey "shawl", dark underwing and relatively thick black trailing edge to the primaries - it could be a small female or just a particularly runty individual, but it is a Black headed gull. Handy refresher!

 

[leifvester]

On first glance, this almost looked like a candidate Bonaparte's gull, but closer inspection reveals a red base to the bill, a lack of grey "shawl", dark underwing and relatively thick black trailing edge to the primaries - it could be a small female or just a particularly runty individual, but it is a Black headed gull. Handy refresher!

I didn't mention earlier because I thought it was a BHG, but it is worth noting that there has been a Bonaparte's gull consistently in this area for a few years now.
Could it be a hybrid?

 

[dwatsonbirder]

I'm not sure if the two species have been known to hybridise, but other than size, I can't see any plumage features or traits indicating Bonaparte's. Others may (will) know for certain. It's helpful to include the location in the title/description too

 

[leifvester]

I'm not sure if the two species have been known to hybridise, but other than size, I can't see any plumage features or traits indicating Bonaparte's. Others may (will) know for certain. It's helpful to include the location in the title/description too

It is interesting to me that Black-headed has hybridised with Med gull and Common gull despite both being different genera.

Whereas I couldn't find any info on Bonaparte's x Black-headed, even though they are the same genus.

 

[pdwinter]

It is interesting to me that Black-headed has hybridised with Med gull and Common gull despite both being different genera.

Whereas I couldn't find any info on Bonaparte's x Black-headed, even though they are the same genus.

Probably because the breeding ranges of Bonaparte's and Black-headed don't overlap whereas there are mixed breeding colonies of BH, Med and Common Gulls in europe.

 

[leifvester]

Righto, so another update. I've been looking for black-headed gulls that look like mine on eBird, and I've been stumbling on photos from North America, where Bonaparte's is common and Black-headed gull is rare.

Have a look at the black-headed gull here: https://ebird.org/checklist/S60372465

Notice the pale grey ear-covert and how far it is away from the eye. Although it appears to have a significantly thicker beak.

The primary feathers in that gull don't look right, but I assume it's just because the gull is moulting.
Also it appears to be small and chubby in flight.

Maybe it's a Bonaparte's x Black-headed hybrid. I wonder how you ever even begin to determine that. I assume before DNA analysis you would have to watch nests + copulation? Has anyone researched the possibility of Bonaparte's x Black-headed, or is it simply that no one has looked deeply into it?

Also as a side note look at this Black-headed gull! https://ebird.org/checklist/S74307863

Look how much is on the primary feathers! Is that a Mew gull x Black-headed hybrid?

 

[leifvester]

And another weird American one: https://ebird.org/checklist/S33854693

It has grey going up the back of the neck, like a Bonaparte's? It doesn't look like the Black-headed gulls that I would normally see. Regional difference? Hybrid?

 

[leifvester]

But there is a gull right here that is pretty similar from Scotland: https://ebird.org/checklist/S161102987

Must just be a huge range of variation.

 

[leifvester]

Just some additional slightly better wing shots.

 

[leifvester]

I've finally found a photo that is basically identical to my bird:

Black-headed Gull variation

As I was passing through Holyrood Park this morning, I sopped briefly at St Margaret's Loch to see whether Edinburgh's resident Iceland Gull...

morgithology.blogspot.com

The only difference really is the black on the head, but I imagine my gull will look just like that in March.

Coincidentally, the blog mentions an Iceland gull, which was also present when I saw my gull. Can't help but wonder if it hints at a regional difference, but I have no idea.

I've struggled to find information about Black-headed gulls, particularly around regional differences and rose-breasted individuals.

I have seen it mentioned that BHG are monotypic, but conversely I have read that bill/head measurements between breeding colonies can differ to the point of making sexing the birds in a reliable and generalised way difficult. I think the example was Polish and Spanish breeding colonies.

There is also the sibiricis subspecies which I can find almost no specific info about.

Even that blog mentions that rose breasted BHGs are well documented, but documented where?
I can't find the reason/research behind this characteristic.

If you do happen to have any info about variations in Black-headed gulls I would greatly appreciate it!

 

[pdwinter]

leifvester

Do you have BWP (Cramp and Simmons) ? Vol 3 (Waders to Gulls) has a lot of information with references to original articles. Unfortunately I gave my 6 volume set to a friend as I ran out of shelf space but it might be worth finding a public library to have a look through it. There are also secondhand copies available at a reasonable price if you do an online search.

In Gulls of the Americas (Howell and Dunn 2007) there is mention of sibiricus - "which averages larger, bigger billed and has later molt timing, breed in e. Siberia (and presumably ranges to Alaska)" . It also says that some authorities regard it as a monotypic.

With regards to rose breasted BHGs I have seen a good number over the years (but unfortunately no images) here in Hampshire and it is mentioned in books - possibly a reference in BWP.

If you have access to Researchgate (https://www.researchgate.net/) - I managed to sign up as I have an alumnus e-mail address (with .ac.uk) from a university I attended nearly 50 years ago - then you will be able to find a lot of articles on gulls.

Hope that helps

 

[wheatearlp]

A link to a pink/rose-breasted BHG attached

Post in thread 'Upton Warren' Upton Warren

 

[pdwinter]

And another weird American one: https://ebird.org/checklist/S33854693

It has grey going up the back of the neck, like a Bonaparte's? It doesn't look like the Black-headed gulls that I would normally see. Regional difference? Hybrid?

There's a thread at Black-headed Gulls with gray hind neck -www.gull-research.org

 

[leifvester]

leifvester

Do you have BWP (Cramp and Simmons) ? Vol 3 (Waders to Gulls) has a lot of information with references to original articles. Unfortunately I gave my 6 volume set to a friend as I ran out of shelf space but it might be worth finding a public library to have a look through it. There are also secondhand copies available at a reasonable price if you do an online search.

In Gulls of the Americas (Howell and Dunn 2007) there is mention of sibiricus - "which averages larger, bigger billed and has later molt timing, breed in e. Siberia (and presumably ranges to Alaska)" . It also says that some authorities regard it as a monotypic.

With regards to rose breasted BHGs I have seen a good number over the years (but unfortunately no images) here in Hampshire and it is mentioned in books - possibly a reference in BWP.

If you have access to Researchgate (https://www.researchgate.net/) - I managed to sign up as I have an alumnus e-mail address (with .ac.uk) from a university I attended nearly 50 years ago - then you will be able to find a lot of articles on gulls.

Hope that helps

Hey Paul,

Thank you very much!
I've ordered a copy of BWP Vol3 ,Waders to Gulls - it was pretty reasonably priced. I don't have a book on waders so that'll be handy.

I also have Gulls of Europe, Asia and North America, which is an excellent book, but definitely has less info on the smaller gulls. Mentions a few things in passing, but not a huge amount of detail.

I'm interested in fairly simple questions like:

• What percentage of Black-headed gulls have rose breasts?
• Is there any regional correlation?
• Is there a diet component to this?
• Are pink breasted Black headed gulls more likely to be smaller?

Research Gate is great, and I did search up a couple of papers on Black-headed gulls. That's interesting that gull-research has a forum, I hadn't realised that either.

 

[Joern Lehmhus]

Bonaparte's x Franklin's Gull (hybrid) - Chroicocephalus philadelphia x Leucophaeus pipixcan - Media Search - Macaulay Library and eBird

Explore millions of photos, audio recordings, and videos of birds and other animals; powered by Macaulay Library and eBird. The Macaulay Library collects, archives, and distributes wildlife media for research, education, and conservation.

search.macaulaylibrary.org

Not Bonaparte's x Blackheaded , but showing that Bonaparte's can also interbreed...

I am not saying yours could be a hybrid, leifvester , but I also don´t have the experience to exclude it as we do not know which traits would be expressed in a hybrid of these two taxa.
Given the fact that unusual blackheaded gulls have been documented, this certainly would seem more likely ...

 

[leifvester]

Bonaparte's x Franklin's Gull (hybrid) - Chroicocephalus philadelphia x Leucophaeus pipixcan - Media Search - Macaulay Library and eBird

Explore millions of photos, audio recordings, and videos of birds and other animals; powered by Macaulay Library and eBird. The Macaulay Library collects, archives, and distributes wildlife media for research, education, and conservation.

search.macaulaylibrary.org

Not Bonaparte's x Blackheaded , but showing that Bonaparte's can also interbreed...

I am not saying yours could be a hybrid, leifvester , but I also don´t have the experience to exclude it as we do not know which traits would be expressed in a hybrid of these two taxa.
Given the fact that unusual blackheaded gulls have been documented, this certainly would seem more likely ...

Thank you very much!

Yes I think I was needlessly going down the hybrid rabbit hole for this one, however I believe (and it is just a belief, nothing more) that there is a Black-headed gull x Bonaparte's hybrid out there, it just hasn't been ID'd yet!

 

[leifvester]

Hey Paul,

Thank you very much!
I've ordered a copy of BWP Vol3 ,Waders to Gulls - it was pretty reasonably priced. I don't have a book on waders so that'll be handy.

I also have Gulls of Europe, Asia and North America, which is an excellent book, but definitely has less info on the smaller gulls. Mentions a few things in passing, but not a huge amount of detail.

I'm interested in fairly simple questions like:

• What percentage of Black-headed gulls have rose breasts?
• Is there any regional correlation?
• Is there a diet component to this?
• Are pink breasted Black headed gulls more likely to be smaller?

Research Gate is great, and I did search up a couple of papers on Black-headed gulls. That's interesting that gull-research has a forum, I hadn't realised that either.

I've done a little more digging, and this is as far as I could get:

Crustaceans in a gulls diet contain Astaxthin which gives gulls the rose colour on the breast.

This would then naturally explain a regional difference, as some areas are going to have more shrimp/crabs than others.

What doesn't make a whole lot of sense, and what I've been trying to figure out is if it's a diet based colouration, then why do relatively few Black-headed gulls have this pigmentation? Why does only a small number have a significantly different diet?

Furthermore, crustaceans typically make up very little of a Black-headed gulls diet. They prefer bivalves (Molluscs) and worms. They don't seem to go out to sea hunting for crustaceans like other gulls do, e.g. Lesser black-backed and Little gull.

Anecdotally, the Black-headed gulls I have seen with the pink breasts are among the smallest birds.
If this holds true, then perhaps the size of the bird effects the EROI for crustacean hunting and they are able to mimic the tactics of the similar sized Little gulls that go out to sea diving into the water.

Just a shot in the dark really. Wasn't able to find the needed information and piece together coherently. A lot of the feeding behaviours and diet were comments, and I wasn't able to get to the sources.