PRAIRIE HORNED LARK 355 



Songs are sung from the ground, from a clod or any other slight 

 elevation, the greatest elevation noted being the roof of a sample 

 apartment put up on the Evanston area; and from the air. The 

 ground songs are similar to the flight songs though rarely as long or 

 as systematically presented. The urge to flight song may come at 

 any time or after an invading male lark has been evicted from 

 occupied territory. Larks will also go into flight song upon ap- 

 proach of a human being or they can be forced to go up by driving them 

 for a time about their territory. 



The climb to flight song is distinctive and usually executed ^vithout 

 a sound from the bird. The songs, in the air, are of two types : A 

 recitative or rapid monotony of notes usually uttered at the begin- 

 ning of the flight song, though occasionally at other periods, never 

 over a few seconds in duration, accompanied by a steady beat of the 

 wings; and an intermittent song uttered while the lark sails, about 

 two seconds in duration, followed by a somewhat longer silent period 

 during which the lark flutters up. The recitative can be transcribed 

 as pit-wit, wee-pit, pit-wee, loee-pit; the intermittent as pit-wit, pit- 

 wit, pittle wittle, little, litle, ledeeee. Large circles are described 

 overhead during the flight song, or the bird heads into the wind if it 

 is strong. The lark closes flight song by a headlong drop to earth 

 with wings tightly folded. 



Female larks seem to be unaware of the males in flight song, 

 though other males note the bird overhead. The territory a bird 

 may occupy in flight song is very extensive. Never were two visible 

 birds noted in such a performance simultaneously. The one in the 

 air is left undisturbed though his performance may carry him over 

 many other lark breeding grounds below. Breeding territories are 

 not vertical for a distance above a few feet ; the flight song territory 

 is something quite different. 



Of several methods employed to determine the heights of larks in 

 flight song, the most accurate was found to be the use of a binocular 

 with an ocular scale. It was determined thus, through measurement 

 of 25 songs, that the lark sings from elevations that vary from 270 

 to 810 feet. The average was 464.4 feet. Differences in height 

 seemed to be individual variations or due to weather. Thirty times 

 flight songs varied from one minute to five; the average was 2.34 

 minutes. Intermittents, regularly given, averaged 11.9 a minute. 



An Evanston bird sang from song posts on the ground, which, during 

 one entire day, varied a few feet from the incubating female out to 

 100 yards. The average was 38.66 yards. Ithaca birds, with bigger 

 territories, sang frequently as far as 150 yards from the nest. 



Fall. — Young larks flock shortly after nest leaving. If the breed- 

 ing ground has become untenable owing to vegetation, they seok 

 other regions. Flocks grow larger through addition of adults in 



