delawarensis Ring-billed Gull

(last update: 10-03-2014 )

Coordinators:
Keith Mueller
Amar Ayyash
Mars Muusse

Index ORG

ring projects
PDF's

1cy June
1cy July
1cy Aug
1cy Sept
1cy Oct
1cy Nov
1cy Dec

2cy Jan
2cy Feb
2cy March
2cy April
2cy May
2cy June
2cy July
2cy Aug
2cy Sept
2cy Oct
2cy Nov
2cy Dec

3cy Jan
3cy Feb
3cy March
3cy April
3cy May
3cy June
3cy July
3cy Aug
3cy Sept

adult Jan
adult Feb
adult March
adult April
adult May
adult June
adult July
adult Aug
adult Sept
adult Oct
adult Nov
adult Dec

adult: March

Ring-billed Gulls vs Common Gulls: comparison from a Dutch perspective - 201402

by: Maartren van Kleinwee (GULLS TO THE HORIZON)- March 06 2014.

Ring-billed Gulls Larus delawarensis are common visitors to Europe with frequent sightings in countries directly bordering the North Atlantic such as Ireland, Spain and Portugal.
Here in the Netherlands however, they are considered rare (see list of observations on Waarneming.nl) and most sightings are quickly uncovered as regular Common Gulls Larus canus due to unfamiliarity by the observer with both Ring-billed Gull and Common Gull.
When I traveled to the USA recently for a short gull-watching trip (see Gull watching in the southern Lake Michigan region (USA) – 201402), one of my aims was to get familiar with Ring-billed Gulls and to find out exactly what differentiates them from Common Gulls.
Below are some personal reflections based on my observations.

Note #1: This article is nothing more than a personal exercise in comparing 2 random groups from both sides of the Atlantic; it should by no means be seen as a definitive comparison between these 2 species; this requires a far higher number of individuals.
Note: #2: All Common Gulls are of unknown origin and photographed in the Netherlands in the months of December, January and February.

Adults

Although it should be quite straight forward to distinguish an adult Ring-billed Gull from a Common Gull, lets compare some of the main features.

Compared to an adult Common Gull, an adult Ring-billed Gull is different in the following aspects:

• Lighter upper parts
• A thicker, stouter bill
• Smaller mirror on P10
• Smaller mirror on P9 or no mirror on P9 at all
• Rarely a mirror on P8
• No black on P4
• Pale yellow iris
• Thinner tertial crescent

Bill and eye color comparison

Note that the bill pattern on the Ring-billed Gulls is very distinct, while the ‘ring’ on the bill of a Common Gull is very faint.
Judging the bill shape and size may look straightforward but can be tricky in the field.
Pitfall: Some Common Gulls can show a light iris and should not be treated as a Ring-billed Gull on that feature alone.

Primary pattern

Q. How does the pattern on the primaries help us recognize an Ring-billed Gull in the Netherlands?
A. Any individual without a mirror on P9 should immediately attract attention.

Tertial crescent

Probably one of the key features of spotting an adult Ring-billed Gull in a group of Common Gulls (especially from afar) is its much reduced white tertial crescent.

Vocalization (see/listen also HERE)

The vocalization of Ring-billed is lower in tone, more nasal than Common and reminiscent of Herring Gull.
Unfortunately I don’t have many recordings of Common Gull vocalizations and they don’t match the type of Ring-billed Gull calls that I was able to record in Milwaukee, but I thought it best to include 2 tracks.

Comments

Although this has been a fully unscientific and random comparison, it has nevertheless been a very interesting and useful exercise for me.
It has highlighted some features that I would otherwise not have noticed (such as the barring on the inner primaries in first-cycle birds) and has made me more comfortable in knowing what to look out for should I come across a Ring-billed Gull-candidate here in the Netherlands.
It has been great to observe Ring-billed Gulls in such large groups and from such a short distance. Unfortunately the same cannot be said of Common Gulls and I was surprised with how few photos I had in my archives of this species.
Finally, I hope that my findings are useful for other birders as well.

Locations

The majority of the Ring-billed Gull photos in this article were taken at the beach at the BP refinery at Whiting, Indiana, USA, adjacent to Lake Michigan.