'Laughing Gull' would be 'Gwylan yn chwerthin' because the noun comes before the verb in Welsh.
As for pronunciation (I'll try my best to do it phonetically for you)
Gwylan-"Gooi-lan" "g" as in "gallivant"then the rest as a drawn out Ooi! emphasis on the "gooi"
yn-"un" as in "bun"
chwerthin-this is tricky "ch" as though you're preparing to spit (sorry closest sound I can think of!)
so "chweh-r-thin" emphasis on the "chweh".
Hope that makes sense?
~*Efo can yn fy ysbryd,a'r heniaeth yn fy ngwaed,rwy'n byw bywyd llawn efo calon Celtaidd*~