A comparative analysis of acoustical signals in pied woodpeckers (Aves, Picoides). Bulletin of the AMNH ; v. 160, article 1

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New York : American Museum of Natural History
"The avian genus Picoides with 33 species is the largest of the nearly worldwide family of woodpeckers (Picidae). Picoides is the subject of vocal analysis involving field, literature, and audiospectrographic studies. Analyzable data were available for two-thirds of the species. The analyses were conducted using quantitative and qualitative techniques, in a manner attempting isolation of descriptive, functional, motivational, and homologous aspects of acoustical signal communication. Vocalizations include Call Notes, Scolding Call, Double Call, Rattle Call, Short Rattle Call, Mistle Thrush Call, Mutter Call, Kweek Call, Wicka Call, Twitter Call, Wad Call, Soft Notes, Distress Trill, Chirp Call, Loud Chirp Call, Squeak Call, Screech Call, and Distress Cry, and there are several instrumental signals (Drumming, Tapping, Wing Rustling). These are described and many are illustrated sonagraphically for species represented by tape-recordings. Summaries are provided for all vocal and instrumental signals that have several or more species represented. Most sounds made by these woodpeckers are formed of three major elements: clicking, squeaking, and ascending sounds. When further data become available, these elements may provide a productive means of analyzing the vocalizations. Aspects of the repertoire briefly discussed are the number and quality of calls, their discreteness, overall tendencies in structure, relative frequency of different calls, and combinations. Each major acoustical signal is discussed functionally, in terms of its 'meaning' and the biological advantages it affords. The array of such signals includes calls that may overlap in function, but differ in occurrence, the distance at which they are effective, and other parameters. Drumming and the Rattle Call are the most important long-distance signals. Call Notes chiefly are contact calls. Rattle Calls function in territorial announcement and defense, but may serve as a contact call in some species. Sexual interactions of various kinds are accompanied by Kweek Calls, with special functions in P. medius and P. borealis. Wicka, Mutter, and Twitter calls mark encounters between individuals and often accompany visual displays. Wad Calls commonly occur between members of a pair. Various nestling and fledgling calls are ascribed functions. Drumming has diverse and often subtle functions, and may differ in structure and function seasonally. It differs from most avian signals in communicating over a distance, aspects of environmental features, e.g., the occurrence of suitable trees for Drumming or nesting. Motivation of the signals is discussed in a framework based on a general arousal scheme and dominance behavior that is directly equivalent to 'aggressive' behavior ethologically. The Call Note indicates arousal, Scolding -- alarm, and Rattle Calls -- aggression, in this context. Kweek Calls of one type usually are submissive; those of another, as well as Wicka Calls, are aggressive. Conflicts between fleeing and aggression find expression in the Mutter and the Twitter Calls, and between aggression and submission in the Wad Call. Hunger, the motivation to flee, or to stay in place usually seem involved in the Squeak Call. Drumming seems related to a special category of motivation with a low threshold that may be elicited by extraneous noises or the presence of a Drumming substrate. An attempt is made to ascribe likely meanings to the signals, based on their information content. Call Notes indicated the location of the sender, and particularly are noted with changes in position. The Rattle Call is self-assertive or aggressive and transmits that information plus the location of the signaler. Scolding and Short Rattle Calls indicate alarm, and convey that meaning. The complex of Mutter, Twitter, Kweek, and Wicka calls give varied information about the sender's motivational state during interactions. Further analysis is necessary to decipher exact meanings, which depend in any event on the social relations existing between interacting individuals. Other calls and instrumental signals are discussed in a similar manner. Homologies are treated, based on similarities in form and the relation of calls to other calls, displays and situations; evolutionary and ontogenetic effects are related to homology within pied woodpeckers, and to some degree with other picid groups. Some acoustical signals, notably Drumming and Scolding, but even Rattle Calls and Call Notes are effective interspecifically in Picoides, between pied woodpeckers and species of diverse woodpecker genera, and occasionally between pied woodpeckers and birds of other families. Taxonomic applications of the data include as major points the monophyly of the genus Picoides sensu Short (1971a), close relationship of arcticus and tridactylus to the villosus subgroup, monophyly of the American group of Picoides, the distinctness and derived state of medius, and of the major group, and the likelihood that the most primitive members of the genus are to be found in Asia among relatives of the moluccensis and canicapillus groups. Vocalizations are described for two hybrid combinations, major x syricus and scalaris x nuttallii, and are more or less intermediate between those of the parental species"--P. 5-6.
109 p. : ill. ; 26 cm.
Includes bibliographical references (p. 105-109).