Home Range and Territory 351 



species that wander by unless they actually intrude on his intended 

 nesting site. Characteristically, the male bird chooses a singing 

 perch, makes himself conspicuous, and, when a potential mate comes 

 to the area, goes through the courtship display. In some species, as 

 for example the house wren, the male may even start building a nest 

 before the female arrives. (No doubt he has to do it all over again 

 when she appears on the scene! ) After the nest is completed and 

 during the period when eggs or young are in the nest, the territory 

 is defended with particular fierceness. 



By carefully observing the movements of a pair of birds for a 

 period of time, the ecologist can determine the position of the unseen 

 boundary lines of their territory. If the birds build a second or a 

 third nest during the same season, these later nests are placed some- 

 where within the original territory. The division of a region into 

 territories by pairs of breeding birds is illustrated in the diagram of 

 Figure 9.16. It will be noted that the territories of birds of the same 

 species do not overlap— indeed, a neutral zone usually exists between 

 them— but the territory of one species may overlap that of another 

 species if no reaction of antagonism occurs between them. 



In a 16-hectare tract of spruce-fir forest in northern Maine 148 male 

 birds of various species were found to have established breeding ter- 

 ritories by a census conducted during a week in June. During the 

 ensuing 3 weeks a total of 302 territorial males were removed from 

 the tract by shooting. Study of the area indicated that new males 

 from a "floating" unmated population moved in and established ter- 

 ritories as rapidly as the former inhabitants were removed. Thus 

 the number of sites suitable for the establishment of territories was 

 shown to be the chief factor limiting the number of birds that could 

 breed in the area (Stewart and Aldrich, 1951). 



The dimensions of the territory or home range may be measured 

 in kilometers in the case of large mammals or birds of prey or in meters 

 or smaller units in the case of smaller animals. Bears may roam over 

 distances of 30 or 40 km, whereas porcupines confine their home 

 activities to trips of a kilometer or so and the home range of beavers 

 is ordinarily less than a kilometer in diameter. The home ranges of 

 the whitetail deer vary in size from about 80 to 120 hectares (200 to 

 300 acres), of the cottontail rabbit from 1 to 3 hectares, and of some 

 kinds of mice from less than i/4 to more than 1 hectare. The daily 

 roamings of prairie deermice in southern Michigan were found to be 

 confined within 2 or 2^/4 hectares, but on different occasions during a 

 breeding season both male and female deermice may travel over an 

 area as great as 4 hectares ( Howard, 1949 ) . The home ranges of box 



