Effect of septal lesions on male song and aggression in the colonial zebrafinch (Taeniopygia guttara) and the territorial field sparrow (Spizella pusilla) (vol 98, pg 167, 1998)

The present investigation assessed the effect of lesions of the septum on m ale courtship and aggression in the territorial field sparrow (Spizella pus illa) and the colonial zebra finch (Taeniopygia guttata). In addition, pair -bonding and a variety of other social behaviors were examined in the zebra finch and dawn song (both the strictly agonistic song type and the multipu rpose song type) was examined in the field sparrow. Zebra finches were test ed in three phases both before and after receiving bilateral electrolytic l esions of the septum or sham surgery. These phases were: (1) competition te sts in which a subject and a stimulus male were exposed to a female in an a djacent cage; (2) sexual behavior tests with a female; and (3) 10-day group cage tests in which subjects were in a mixed-sex environment. Aggressive b ehaviors (chases, threats, beak fences and pecks) were significantly reduce d by septal lesions but not by sham surgery. Directed song (courtship) was significantly reduced in sexual behavior tests, with similar trends in othe r testing phases. Male field sparrows were tested 2 days pre-surgery and 2 days post-surgery in outdoor aviaries placed in their natural habitat. Test s consisted of dawn song observations and observations of courtship and agg ression following introduction of a female to the subject's aviary, which w as followed 10 min later by the introduction of another male (without remov ing the female). Septal lesions significantly facilitated both overt aggres sion (chases) and the number of simple (multi-purpose) songs. These results provide evidence that the septum participates in the regulation of male ag gression and song in songbirds, and further suggest that variations in sept al function may exist between territorial and colonial species. (C) 1999 El sevier Science B.V. All rights reserved.