The life of an Irish birder

Winter birding: Caspian gull

hybrid in Dublin?

On the 9th of December 2013 a suspected second-winter Caspian gull was photographed at Sean Walsh park, Tallaght, Co. Dublin, found by Graham Prole. The bird had initially been suspected to have been a yellow-legged gull. Though images had been sent around and came to a conclusion that it was most likely a Caspian. I was lucky to see this bird as a second-winter when I was a teenager still in secondary school. I had just assumed with my lack of knowledge on gulls that this bird was a Caspian gull! Though after hearing some comments when the bird had returned as a third-winter and then as a subadult/adult the bird was being questioned as a possible hybrid. I then began to take some more interest in this bird, I had as a teenager put this bird on my Irish life list. Though, now have subsequently taken it off as I do in fact think this bird was a hybrid. I have since seen two adult Caspian in Ireland thankfully!

Hybrid Caspian x lesser black-backed gulls are something that are not well covered in literature to date. But given the breeding range of both species it is highly likely that these species do hybridize with one another. It was nice to delve into the identification of this Dublin bird and shed some more light on this subject. This bird was also recorded by Niall Keogh on Sandymount strand, Dublin on March the 10th 2018 with lesser black-backed gulls and Niall had also suggested that this bird maybe a Caspian x Lesser black-backed.

Presumed Caspian x lesser black-backed gull, Sean Walsh park, Tallaght, Dublin - Pat Lonergan

Second-winter:

As a second-winter this bird was thought to be fine for a Caspian, though perhaps a tad dark on the mantle and lacking a white spot on P10 throughout it's second-year which is not a good feature for a Caspian.

Presumed Caspian x lesser black-backed gull, Sean Walsh park, Tallaght, Dublin - Pat Lonergan

Presumed second-winter Caspian x lesser black-backed gull, Sean Walsh Park, Tallaght, Dublin - Stephen Lawlor

Presumed second-winter Caspian x lesser black-backed gull Sean walsh park, Tallaght, Dublin - Jim Bowman

Presumed second-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin - Dick Coombes

In terms of viewing this image, this bird looks like what you would expect in quite a classic Caspian of this age. White underwing, common gull like face, eye, slightly drooping bill and long winged all favour a Caspian.

AS a third-winter:

The bird had presumably returned for its second winter now as a third-winter bird. And now perhaps looking even more hybrid like. The mantle tone is very striking in terms of just how dark it is for a pure Caspian, resembling a closer shade to a Scandinavian herring or hybrid herring x lesser black-backed.

Presumed third-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin, 16th Nov 2014 - Stephen Lawlor

Primary 10 (P10) on this bird is not a good pointer towards a pure Caspian as it should be black with a pure white unbroken tip. P5 also tends to show a neat black band rather like that of a yellow-legged gull.

Presumed third-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin, 22nd Nov 2014 - Dave Fox

Presumed third-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin - 7 Dec 2014 - Stephen Lawlor

In this image the bird appears paler, though this is due to the strong sunlight hitting the bird. The mantle tone appears paler than seen in previous images.

Presumed third-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin - 10th Dec 2014 - Conn O’Brien

Even though this image was captured in the fading winter light it does give a good reflection of just how dark the upper parts are on this hybrid. The hind neck streaking is rather Caspian like.

Presumed third-winter Caspian x lesser black-backed gull Sean Walsh park, Tallaght, Dublin 8th Jan 2015 - Dave Fox

Sub-adult/adult:

Presumed sub-adult/adult Caspian x Lesser black-backed gull Sean Walsh park, Tallaght, Dublin - Stephen Lawlor

Presumed sub-adult/adult Caspian X Lesser black-backed gull Sean Walsh park, Tallaght, Dublin 20th Dec 2015 - Stephen Lawlor

This image gives a caspian and lesser black-backed feel, from the mantle tone to the bill. I can see both species in this bird. Fleshy pale leg colour. This bird is also not the bulkiest like many Caspian are considered to be, though Females may vary of course.