Strophe Length Research Articles

THE SINGER AND THE SONG: ON THE RECEIVING END OF BIRD SONG

SummaryVariation in singing behaviour between males can involve fixed differences such as the song type composition of repertoires, as well as more flexible effects such as matched counter‐singing (Krebs & Kroodsma, 1980; Section III. 4), differences in bout length (the number of songs in a period of song) and changes in strophe length. Short‐term strophe length changes seem to be related to the willingness and ability of males to respond strongly to playback. Whether this is because strophe length indicates motivation or the degree of exhaustion of the neuromuscular song‐production system, or both, is currently unclear.

Male quality and territory quality in the great tit parus major

In this study there was no positive significant relationship between the quality of male great tits, as measured by average strophe length (a strophe is a short burst of song), and territory quality. (1) Males singing longer strophes did not defend territories in areas of higher recruitment, and (2) naturally settling males were better singers than replacement birds were. The second result was probably caused by a difference in age composition of the two groups, because naturally settling yearlings and replacement yearlings did not differ significantly in average strophe length. These observations on a non-migratory species are in contrast to those of several other studies on passerine birds, which were mostly concerned with migratory species. The relationship between male quality and territory quality is predicted to be closer in species that migrate than in non-migratory species.

The anti-exhaustion hypothesis: a new hypothesis to explain song performance and song switching in the great tit

This paper describes the results of a detailed analysis of 52 song bouts, recorded from 22 great tits, Parus major, during the dawn chorus. A song bout consists of a number of song bursts (called strophes) separated by periods of silence. High quality males, as measured by average strophe length, sang their bouts with a higher percentage performance time (i.e. the percentage of time spent singing in a bout), but the average number of strophes per bout was not related to male quality. In 31 of 52 bouts there was a systematic decrease in the percentage performance time throughout the bout. This was mainly caused by a prolongation of the pauses between the strophes, and sometimes by a shortening of the strophes. Both high and low quality males sang bouts with and without this decrease in the percentage performance time. Bouts that started with longer strophes and/or shorter inter-strophe pauses showed on average a more rapid decrease in the percentage performance time, and contained fewer strophes, than bouts that started with shorter strophes and/or longer inter-strophe pauses. After switching to another song type the males again used longer strophes and/or shorter inter-strophe pauses. An ‘anti-exhaustion’ hypothesis is proposed and discussed. This hypothesis gives a mainly causal explanation for the existence of song switching and song repertoires in passerine birds.

Functional Aspects of Singing in Male and Female Uraeginthus bengalus (Estrildidae)

AbstractBoth sexes of the African estrildid species Uraeginthus bengalus sing regularly. Song structure and the context of singing were studied in males and females under aviary conditions. It was found that: Males and females have a similar song differing merely in strophe length, medial length being 1.38 ± 0.47 s in females and 2.58 ± 0.63 s in males. Males sing during nesting, laying, incubation and broodcare, but also long before, with a remarkable activity peak at the beginning of incubation, whereas females hardly sing at all during the egg‐laying and incubating phases, and their singing peak is long before laying starts. In 52 % of all cases the male responds to his female's song during the pre‐incubation period. His reaction includes singing, courtship display and elements introducing copulation.