608 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



immediately. During the morning twilight hours in early spring, the 

 male moves around the limits of his territory giving a rapid loud tsip 

 note. This behavior, constant enough to be useful in census taking, 

 ceases with the onset of nesting activities. 



Population density reaches its maximum in disturbed areas such as 

 the campus of the University of California at Berkeley. Here the 

 vegetation is composed of ornamental shrubs, usually in a linear 

 arrangement along buildings, streams, or paths, with much of the 

 area in lawns. This pattern of vegetation provides nesting cover in 

 dense shrubs from 2 to 5 feet tall, foraging areas on the lawns for 

 these primarily ground feeding, seed-eating birds, and escape cover 

 close to the foraging and nesting areas, mandatory because the 

 towhee's short, rounded wings do not allow long or fast flight. The 

 habitat thus provided appears optimum for the brown towhee as 

 indicated by its abundance, 48 pairs per 100 acres. The territories, 

 1-2 acres in size, are remarkably uniform. In a study of avian re- 

 sponses to artificial habitat near Dillon Beach, Calif., F. A. Pitelka 

 (1942) observed one once in this coastal locality, but found no towhees 

 breeding. 



In natural areas such as the Berkeley hiUs, where the shrub vege- 

 tation of the west-facing slopes grows along drainages, territories are 

 larger and longer, following the intersection of shrubs and grass. 

 Here individual territories may be over 5 acres in size. 



Courtship. — Courtship behavior has not been described in great 

 detail. On several occasions during the breeding season the male has 

 been observed approaching the female with wings slightly drooped 

 and quivering. Both wings may quiver in unison or alternatingly. 

 Copulation may occur on the ground, but on one occasion it was 

 observed on the top of a three-story building. The female assumes 

 a position with the head tipped slightly forward and down and raises 

 her tail. The male then mounts. In aU cases observed both sexes 

 were silent during coition. 



Nesting. — Most brown towhees at Berkeley start nest building 

 by mid-April, and some pairs complete three nestings successfully by 

 the end of summer. Incubation by the female alone takes 11 days 

 and the first clutch of three or four usually hatches in late April. After 

 8 days in the nest, the young fledge enough to leave it. The period of 

 dependence on the adults varies. If there is no renesting, the young 

 may remain with the adults from 4 to 6 weeks ^ but when the adults 

 renest they drive the first young from the territory when the next 

 clutch hatches. 



The nests are rather bulky affairs of grasses and twigs of many kinds, 

 and not too weU constructed. Built from ground level to more than 

 35 feet up in a variety of trees and shrubs, the optimum height appears 



