For anyone interested, the excellent paper by Pat Lonergan and Killian Mullarney "Identification of American Herring Gull in a western European context" (Dutch Birding, 2004) is available with thanks to the authors and Dutch Birding at the Irish Rare Birds Committee website - link below. Remarkably the classic American Herring Gull first photographed at Nimmo's Pier, Galway as a juvenile in January 2004 has been returning every winter since and is back at the same location again this winter.
http://www.irbc.ie/notes/pdf/Identifica ... ergan).pdf