EXPLANATION OF KEYS AND DESCRIPTIONS 13 



EXPLANATION OF KEYS AND DESCRIPTIONS 



The artificial keys to the orders, families, genera, and species given in the follow- 

 ing pages are for North Carolina birds only, and apply principally to adult males, 

 the females and immature birds being included only when the distinguishing charac- 

 teristics of size and color sufficiently approach those of the male to render this 

 possible. Furthermore, when a marked change of plumage occurs during the year 

 the appearance of the bird in the spring, or breeding season, is the one to which 

 reference is made. A series of keys sufficient to take account of the various plumages 

 which different species assume throughout the year would be so voluminous and 

 intricate as to be of little real service to the student. In practice, however, it will 

 be found of little difficulty to determine the order and family to which any bird 

 belongs; in fact, many females which are very dissimilar to the male may be traced 

 to their respective genera, after which a little examination of the careful description 

 given under the specific names will soon render identification complete and satis- 

 factory. 



To the student who has had little or no experience in the use of keys of this 

 character, the following explanation of their use may be of assistance. 



Take, for example, the key to the genera of the swallow family, which is as fol- 

 lows: 



1. Color of upperparts brown. See 2. 



1. Color of upperparts more or less blue or blue-green. See 3. 



2. Outer web of outer primary with stiff recurved hooks. Stelgidopteryx. 



2. Outer web of primary without recurved hooks. Riparia. 



3. Tail forked for more than half its length. Hirundo. 



3. Tail not forked for more than half its length. See 4. 



4. Length more than 7 inches. Progne. 



4. Length less than 7 inches. See 5. 



5. Throat white. Iridoprocne. 



5. Throat chestnut. Petrochelidon. 



Suppose, now, we have a specimen of the common Purple Martin, and wish to 

 identify it by the key. We look at the two branches of "1," and the color being 

 more or less blue, and not brown, it falls under the second branch, which refers to 

 "3." As the tail is only slightly forked, it falls under the second division of "3," 

 which refers us to "4," and, the length being over 7 inches, it comes under the first 

 division of "4," which tells us that the genus should be Progne. We then turn over 

 to where the genus Progne is mentioned, and find that only one species of the genus 

 Progne, namely, the Purple Martin (Progne subis), occurs in the State; hence this 

 must be our bird. 



If we had a Barn Swallow, it would "key" down the same way until we reached 

 "3," where the deeply forked tail would put it in the first division of "3" and indi- 

 cate that it belonged to Hirundo. A Rough-winged Swallow, on the other hand, 



