552 



NATURALIST'S GUIDE TO THE AMERICAS 



Some "adaptations" of the life of 



the grassland to geographic 



conditions (S. S. V.) 



Birds. The birds of the grassland 

 possess two or more of the following 

 characteristics : 



1. Nests are necessarily built on the 

 ground. 



2. Many kinds sing while on the wing. 

 Examples are the lark bunting, long- 

 spur, Sprague's pipit, and frequently 

 the western meadowlark and horned lark. 



3. The songs and calls are loud com- 

 pared with those of birds of woodland 

 or prairie. Because of the climatic con- 

 ditions of the grassland, representatives 

 of species in many cases are farther 

 apart than in most other areas. Calls 

 and songs fulfill their chief purpose 

 only when they are heard by other 

 individuals of the species, and there- 

 fore need to be relatively loud in the 

 steppe. 



4. Social flocking'" is less prominent 

 than among the birds of the woods, 

 water, or prairies, where not only do 

 various species migrate in large flocks, 

 but troops wander socially about in 

 other seasons, especially in winter, and 

 several abundant species nest in colo- 

 nies. The grackle, crow, swift, swal- 

 lows, night herons, blackbirds, marsh 

 wrens, numerous water-birds, and the 

 bobolink and dickcissel are examples. 

 If the cliff swallow v/hich nests here and 

 there in the badlands, be excepted, none 

 of the abundant birds of the steppe nest 

 in colonies. The scattered distribution 

 of life on the steppe, noted in the preced- 

 ing paragraph, is exemplified in the dis- 

 tribution of the nests of the steppe 

 birds. The lark bunting and longspurs, 

 and occasionally the Swainson's hawk 

 migrate in flocks which, however, soon 

 break up. Flocking in the winter is 

 largely accidental. Birds gather where 

 food is available, in areas swept by the 

 wind or in patches of taller vegetation 

 which are not snow-covered. Weedy 



"> Statements made by Craig, Wallace: "North 

 Dakota Life," Bull. Am. Geog. Soc. XL, pp. 401- 

 415, 1908, have led to the erroneous generalization by 

 a few animal ecologists unfamiliar with birds that 

 gregariousness is a characteristic of grassland birds 



fields, where seeds are abundant, often 

 are the site of such gatherings. 



5. Many have the ability to withstand 

 strong wind. For example, seed-eaters 

 feed during the winter in apparent 

 comfort on wind-swept hills. 



6. Females and nestlings are almost 

 all protectively colored. This seems 

 required by the exposure of the nesting 

 sites. 



7. Most species are highly migratory. 

 Few individuals remain dtiring winter, 

 and these are of species different from 

 those of summer, e.xcept in the case of 

 the desert horned lark. Even this 

 species migrates somewhat. The aridity 

 and the inactivity of other life combine 

 with the cold to encourage the desertion 

 of the steppe during the winter season. 



8. Most birds have the ability to 

 withstand the intense heat of the sun. 

 This is especially notable in the nestlings 

 which are often on dark ground. 



9. The birds of the grassland of neces- 

 sity must require but little drinking 

 water. Heavy dews are rare. 



10. The power of acute long-range 

 vision appears to be possessed by a much 

 larger number of birds of the steppe 

 than by those inhabiting woodlands. 

 Clearness of atmosphere, slightness of 

 relief over large areas, and the widely 

 scattered distribution of life all probably 

 have encouraged the development of 

 acute long-range vision. 



Mammals. The mammals of the 

 grassland have all acquired two or more 

 of the following characteristics: 



1. Ability to run swiftly. Examples 

 are the antelope (32 mi. an hour), jack- 

 rabbit (28 mi. an hour), coyote (24 mi. 

 an hour), kit fox or swift (20 mi. an 

 hour), and gray wolf (20 mi. an hour).n 



It is possible to run more swiftly upon 

 dry grassy plains than through woods or 

 brush, in marshes or across rugged 

 tracts. For this reason the inhabitants 

 of such plains have come to be the 

 fleetest runners. Long distance run- 

 ning was developed among some of the 



"Velocities are those attained by the normal, 

 healthy adult when pursued by greyhounds, and 

 are quoted from Seton, E. T.: Life Histories of 

 Northern Animals. (New York, 1909 ) 



