Sometimes in a choice you will encounter two phrases separated by 

 OR. The intended meaning is much stronger than a lower case "or". This 

 means that within the choice, you are being given two or more GROWS of 

 characters, only one group of which will fit the specimen. Both phrases, 

 separated by OR t cannot fit. If they do, something is not correct 

 (perhaps you made a wrong choice earlier). 



If you find a bird carcass with a head, and this is often the case, 

 a collection of drawings is provided with which you match bill shape 

 and size (Plates 1-33) by holding the bill up to the drawing. A WORD OF 

 CAUTION: Please realize that slight variations in size and shape of 

 bills are to be expected. IN CASES WHERE THERE IS OVERLAP THE DRAWINGS 

 MAY GIVE YOU ONLY A GROUP OF SPECIES, and only a rough idea of the two 

 or three most likely ones. For example, Glaucous and Glaucous-winged 

 Gulls overlap in size to a great extent, and also overlap in size with 

 several other species (Western, Herring, Thayer's Gulls). In many 

 species, we provide small and large examples of each. Please use the 

 keys, too - do not rely entirely on the drawings, especially when 

 dealing with loons, storm-petrels, jaegers, gulls and terns. 



As another aid to identification a section of "Species Accounts" is 

 given for both birds and mammals. These provide information on the usual 

 timing and locality of occurrence, and in many cases some additional 

 identifying characteristics. 



MARINE BIRDS 



In this manual, marine birds include avian species that spend a 

 significant part of their life cycle in contact with the marine environ- 

 ment. In more practical terms, the species included are those likely 

 to occur dead on beaches in the prescribed geographic area. Not in- 

 cluded are wading birds (herons, egrets, flamingoes, storks, etc.), 

 waterfowl that rarely stray from freshwater, and rails (other than the 

 American Coot). These birds do, but very rarely, occur dead on marine 

 beaches, as do almost any species of land bird. One should be especially 

 aware that pigeons (Rock Doves) are, in fact, found dead on beaches more 

 often than many of the rarer marine species included in the key. As 

 will be mentioned later, if you find a footless and headless 

 pigeon specimen, you will likely try to key it out as a tern. 



MEASUREMENTS OF MARINE BIRDS 



Many choices require measurements of body parts in metric units. 

 You will thus need a ruler, especially when size differences between 

 two species are small. The ruler presented on the back cover will 

 usually suffice but not always. Sometimes, the measurement is designed 

 only to provide the general difference in size between species; that is, 

 instead of stating in a choice that the carcass is "large" vs. "small" 

 (very relative terms) we quantified the difference using real measure- 

 ments. The measurements are taken as follows: 



