The monotony-threshold in singing birds

TitleThe monotony-threshold in singing birds
Publication TypeJournal Article
Year of Publication1956
AuthorsHartshorne C
JournalThe Auk
  1. Variation, both of behavior and of stimuli, is a biological necessity. This explains many facts about bird songs. 2. Song-behavior has gradations of "versatility" and of "continuity": the first concerns the number of different songs, variations, or phrases, and the extent of contrast between them; the second is the ratio between the amount of singing in seconds, and the total "performance period" as inclusive of "substantial pauses,", if any. 3. Discontinuous singing (pauses over 70%) need not be versatile, for (it is argued) the pauses exceed the span of vivid memory; singing lacking versatility and yet highly continuous (pauses less than 50%) is least likely to escape the "monotony-threshold," and hence not likely to occur. Actually it is rare. 4. The threshold is a variable, depending inversely upon level of nervous organization. Indicative of a low level–a high threshold, great tolerance for monotony–is a lack of clear musical contrasts within the basic song pattern, as well as in its reiteration without ample pauses or variations. The second deficiency is found only in association with the first. 5. Families in which continuous singing prevails–thrushes, thrashers, vireos–are also prevailingly versatile; the prevailingly non-versatile groups, Parulidae, Emberizinae, are prevailingly discontinuous, and the few continuous members of these are also the most versatile. Groups or species intermediate in one respect are intermediate in the other. 6. "Exceptions" are few and not inexplicable in terms of the same principles. 7. Song-development exhibits a trend toward "unity in variety,"i.e., beauty, which is to be expected if human nature is a further unfolding of tendencies pervading all life.