Dr. Seuss was (in addition to being a beloved author) a political cartoonist for the New York Daily newspaper .   From 1941 to 1943 he tackled racial issues as will as the world war that was currently going on.  

In this particular comic Seuss critsizes Americans late entry into the war.  The carefree bird (a charicurized Bald Eagle representing American involvement) sits leisurely on its tree as another bird (this one looking much more malevolent with its engraven swastika representing Nazi Germany) tears down the last standing tree other than the American one.   The Eagle says “Ho Humm!”  to show its apparent disconcern.  The colloquial language accentuates this.   The Eagle also shows is blatant ignorance by expecting immunity from the Nazi bird.  Situational irony exists in the the picture since we know the actions taken during the actual war.   Seuss propose was to encourage people to support the war.   He tried to get people to resist the atrocities occurring overseas.