GREAT 

 BLACK- 

 BACKED 

 GULL 



APRIL 



MAY 



MONTH 

 JUNE I JULY 



AUG. 



<L 



BROODING 



EGG LAYING 

 INCUBATION 

 "^ HATCHING 



FLEDGING 



< 



SEPT. 



> 



HERRING 

 GULL 



< 



EGG LAYING 

 INCUBATION 



HATCHING <C r ^ ^^ 



BROODING 



FLEDGING \^ 



> 



LAUGHING 

 GULL 



ARRIVAL <^ 



EGG LAYING ^ 

 INCUBATION ^ 



HATCHING 



< 



REFERENCE: 



1 Clark 1968: p5S-56 



2 Bent 1921 



3 Palmer 1949 



Figure 6. Estimated breeding chronology of three species of gulls nesting in Maine. 



41 



