Red-billed vs Silver Gulls

To: "Ross Silcock" <>
Subject: Red-billed vs Silver Gulls
From: "Frank O'Connor" <>
Date: Sat, 26 Jul 2003 19:43:33 +0800
At 14:40 24/07/2003 -0500, Ross Silcock wrote:
Interesting discussion by Rohan on diffs between Silver and Red-billed
Gulls.  The following pics show the difference in P8 (alt plumage) very
well- shouldn't be too tough to pick out in flight.

Have I read this correctly that you are suggesting that you can identify the two based on whether there is a window in P8?

I don't think that this is true?  Ron Johnstone at the WA Museum published a paper on Silver Gulls in Australia :

Johnstone, R.E., Distribution, Status and Variation of the Silver Gull Larus novaehollandiae Stephens, with Notes on the Larus cirrocephalus species-group, Records of the Western Australian Museum 1982, 10(2):133-165

He says that he can identify Silver Gulls to which part of Australia that they bred based on the size and number of primary windows, and a few other characteristics such as the tips of the primaries.

In particular, the Silver Gull north of Shark Bay in WA doesn't have a window in P8.  Similarly in the Recherche Archipeligo on the south coast of WA.  In between the window is very small.  In New Caledonia, only P10 has a window.

Ron sent me this paper, when I was asking about a gull I saw in Broome in February 2002 with no windows in the primaries and a longer slender bill.  I wanted it to be a Slender-billed Gull, but I had to conclude that it was a Silver Gull, maybe from the New Caledonia population.

Frank O'Connor           Birding WA
Phone : (08) 9386 5694              Email : Birding-Aus is on the Web at To unsubscribe from this mailing list, send the message "unsubscribe birding-aus" (no quotes, no Subject line) to
<Prev in Thread] Current Thread [Next in Thread>

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the birding-aus mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU