Wilson’s 
Oceanites oceanicus 
Galapagos 1 - Qceanodroma tethys 
Graceful - Oceanites gracilis 
Size is mainly when two species are seen together. However, 
the first three species are considerably larger than the last two 
and with a little practice one. should be able to tell these two 
groups apart when only one bird is present. 
II. Tail 
A. 1. Forked 
Leach’s 
2. vs. Slightly forked or not forked 
Wilson’s, Hareourt’s, Graceful, Galapagos 
B. Amount of white in tail vs. amount of black 
1. Black much greater than white 
Graceful Storm Petrel 
2. Wnite much greater than black 
Galapagos Storm Petrel 
These two species are separable from the other three by 
this character alone. 
3 . White and black about equal 
Wilson’s Storm Petrel 
Harcourt’s Storm Petrel 
White slightly less than black, usually with black line 
through white rump 
Leach's Storm Petrel 
As far as this character goes, the last three species are 
very similar. It is necessary therefore to use the forked tail 
of the Leach’s to distinguish it from the other two species. 
Wilson’s and Harcourt’s Storm Petrels are the hardest two species no 
