EASTERN HOUSE WREN 117 



between two males in adjoining territories becomes most vigorous when an 

 unattached female enters the area. * * * The male whose song is most stimu- 

 lating to her ears would seem to have the advantage. 



In addition to song, territories are also defended by the wren's 

 assuming threatening postures sometimes accompanied with scolding, 

 chasing, or physical combat. 



Kendeigh says : 



In the establishment of nest-sites, house wrens may destroy the nests, eggs, 

 or young of the same or diffei'ent species, or even the adult birds. Although there 

 is considerable individual variation in this aggressive behavior, it tends to be 

 most intense during years when the total house wren population on the area is 

 highest. * * * 



Territories in the Hillcrest area average 1.0 acre * * * j^ si^e. * * * 

 The size of the territory varies inversely with the size of the house wren popu- 

 lation and does not exert a limiting influence on the total numbers of the species 

 in the area until it approaches the minimum compressible limit. The adult birds 

 restrict their intensive daily activity to limited parts of the territory but eventu- 

 ally cover the entire area. * * * 



The successful mating of two birds of opposite sex appears to depend on their 

 physiological and psychological readiness, their ability to stimulate each other 

 sexually, the location and character of the teri-itory [and] nest-site together 

 with the nest foundation begun by the male, and finally their freedom from other 

 activities. 



Territory is maintained throughout each breeding period and breeding season, 

 although there may be some decrease in activity as nesting progresses. This 

 continuance of territory may be correlated with the tendency toward polygamy 

 manifest in the male, with the use of the same territory for later matings, and it 

 may also involve the need for a constant and readily available source of food 

 and for freedom from annoying intruders. Primarily, however, the territorial be- 

 havior is most closely linked with the acquiring of a first mate. There is no 

 evidence that territory is maintained at any other than the breeding season of 

 the year. 



Courtship. — ^With the arrival of the female an ardent courtship 

 begins. They have an extensive repertoire of songs and call notes, 

 which are used for various occasions and for purposes of intercom- 

 munication. Both males and females have a habit of quivering their 

 wings when excited, which is most pronounced during the mating 

 process but is evident also when the birds are disturbed or scolding. 

 The position of the male's tail is also a good indicator of the degree 

 of his excitement. During ordinary singing it is kept lowered, but 

 when his courtship song is intensified, or at times when he is scolding, 

 the tail is tilted upward. During copulation it is vertical or tilted 

 forward at an acute angle. 



Much excitement is manifested during the inspection of available 

 nesting sites, some of which have already been selected and partially 

 filled with sticks by the male. The female has opinions of her own 

 resulting in violent domestic controversies that intersperse their 

 passionate courtship antics. The female may refuse the nest proffered 



758066 — 48 9 



