Several people have been of great help to picture skulls on these pages. Some have lent me skulls from their collections and others helped identifying specimens. A few have contributed by reading critically the first versions and laid their finger on mistakes and misinterpretations of the taxonomic confusion that surrounds several genera. Quite a number of people who had visited this site  have encouraged me to go on with this initiative with their helpful suggestions.

Special thanks to Bernie Zonfrillo (Univ. of Glasgow) for his comments and making several skulls and pictures to my disposal. Bob McGowan (Birds Department, Royal Scottish Museum Edinburgh) for his hospitality and letting me take pictures from the collection of the Edinburgh museum, Tineke Prins and Cees Roselaar (Zool. Mus. Amsterdam, now Naturalis, Leiden), Kees Camphuysen (NIOZ; Royal Netherlands Institute for Sea Research, Texel, The Netherlands) and Mardik Leopold (Imares Research Institute, Texel, The Netherlands) for the Alcid specimens from the Tricolor oil spill and many other specimens.
Jan Andries van Franeker, Jeroen Creuwels and Ruben Fijn (Imares Research Institute) made it possible to complete the whole line of fulmarine petrels from material they collected in the Antarctic.
Joel Bried (Department of Oceanography and Fisheries, Horta, Azores) for his help on Cory's Shearwaters. John Borg (BirdLife Malta) for Mediteranean shearwaters. Mike Imber (Dept. of Cons. New Zealand) for identifying a  mystery Pterodroma. Jens Kjeld Jensen, Martin Heubeck and Dan Turner for sending me Razorbill and Guillemot heads of ringed birds. Michael Brooke (Univ. of Cambridge), Roberto Bao (Univ. La Coruña, Spain), Jacob Gonzales Solis (Univ. of Barcelona, Spain), Pierre Ryan (Canadian Wildlife Service), Hannah Nevins (Oikonos), Nils Guse (Universität Kiel, Germany), Wouter van Gestel (Univ. of Wageningen, The Netherlands), Ruud van Halewijn, Ewold Horn, Joe Temper, Marc van Leeuwen, Noel Shillcock, Jennifer Lavers, Jens Kjeld Jensen (Faeroer), Steve Holiday and Tasha for providing me with valuable specimens. Joost Pompert (Falkland Island Fisheries Department) for his help in obtaining material from the Falklands.
Peter Hodum (Oikonos, USA) is thanked for his hospitality and help at Robinson Crusoe Island, Chile. Willem Beekhuizen for always keeping an eye open for seabird material and being great company while roaming Japanese beaches and for his advice. 
Eric Preston, Peter La Tourette, Kees Camphuijsen, Jan Andries van Franeker, Lex van Groningen, Marc van Leeuwen, Robin Newlin en Gerard Visser generously allowed me to use their beautiful seabird pictures. Marcello Stucchi provided some pictures of Booby skulls.
Stephan Lampe who generously spent his time to build the new design of this website and showed me te way to a content manageable website.

And last but not least I owe a lot to Sjany, my wife, who has to tolerate the smells and other inconveniencies of my collecting and cleaning dead seabirds and still enjoys accompanying me searching tide lines and interesting seabird places.

Links to the websites of people, projects or institutions who have been of help: