TABLE 2. SIZE OF THE NINE ORIGINAL TERRITORIES OCCUPIED IN 1960. ========================================== | Date first | Territory | occupied | Dimensions -------------+--------------+------------- 1. | May 3, 1960 | 1.6 acres 2. | May 5, 1960 | 0.6 acre 3. | May 7, 1960 | 0.26 acre 4. | May 11, 1960 | 1.03 acres 5. | May 12, 1960 | 2.07 acres 6. | May 14, 1960 | 3.1 acres 7. | May 13, 1960 | 1.7 acres 8. | May 14, 1960 | 0.46 acre 9. | May 14, 1960 | 0.4 acre -------------+--------------+------------- Average 1.25 acres _Maintenance of Territory_ Except in the early stages of nesting, territory is maintained primarily by song. In the period of incubation a male regularly patrols his territory between sessions of sitting on the eggs. He sings several songs from each of several perches. A male follows a predictable path, rarely traveling more than 150 feet from the nest. Incipient patrolling is seen early in the breeding season when territorial boundaries are in a state of flux. The male White-eyed Vireo travels a semi-predictable route, as does the Solitary Vireo (R. F. Johnston, MS). According to Lawrence (1953:50), the male Red-eyed Vireo has a distinct singing area completely divorced from the nest area dominated by the female. Southern (1958:109), working with this same species in Michigan, did not recognize separate areas, but found that the male wandered randomly over the territory. In a species so highly active as the Bell Vireo, the degrees of hostile action associated with an encounter overlap in such a fashion that no clearcut distinction can be drawn among the various displays. Nevertheless, certain generalized patterns are characteristic of all situations in which members of this species are in a state of anxiety. The threat displays described in the succeeding paragraphs may all be utilized within as little as two minutes; mutual agonism may be terminated at any stage by concerted attack of the dominant bird. 1. Vocal threat. When an intruder is discovered the resident male markedly increases his rate of singing. The alarm note, _eh-eH-EH_, is the first call uttered during the nestbuilding and egglaying periods. 2. Head-forward threat. If the intruder does not flee, the resident male adopts a specific threat posture. The head and neck are extended. The feathers of the crown are erected, but those of the body are sleeked. The bird crouches slightly and the tail is flicked laterally, but not fanned. The intensity of the singing increases and is supplemented by scolding, also delivered at a rapid rate. The intruder normally retreats at this juncture.