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and Summary The influence of testosterone on the general architecture of the song of castrated canaries was studied. Testosterone was applied to juvenile and adult castrated birds by silastic implants of testosteronepropionate. Song parameters such as frequency distribution of pauses between vocalizations, length of tours and stability of elements within a tour were measured. 1. An adult castrated male is able to sing spontaneously; these songs coincide in frequency distribution of pauses, length of tours and stability of elements within a tour with the characteristics of autumnal song. These parameters reach values typical for fullsong after one week of hormone treatment. 30–40 days after the first implantation an obvious elongation of tours occurs. 2. Young castrated birds do not sing when adults without hormone replacement. The pause frequency distribution typical for fullsong is established after one week of testosterone treatment. These animals showed the same elongation of tours after a longer hormone therapy (30–40 days). The stability of elements within a tour needed 30–40 days to reach fullsong values. The influences of testosterone on specific levels of hierarchical song organization were discussed: there is an increase of motivation; the syntax of fullsong is activated by the hormone treatment; a differentiation of motor capabilities is induced in young castrated birds. Zusammenfassung Kastration und Hormonsubstitution (Silasticimplantate mit Testosteron‐propionat) bei männlichen Kanarienvögeln ergaben folgende Auswirkungen auf das Gesangsverhalten der Tiere: 1. Ein adult kastriertes Tier singt spontan; dieser Gesang entspricht in seiner Pausenverteilung, seiner Tourenlänge und der Stabilität der Elemente innerhalb der Tour dem Herbstgesang. Nach einer Woche Hormonbehandlung werden für diese Gesangsparameter die für den Vollgesang üblichen Werte erreicht. 30–40 Tage nach der ersten Implantation kommt es zu einer auffälligen Tourenverlängerung. 2. Jung kastrierte Tiere singen adult ohne Hormonsubstitution nicht. Die Pausenverteilung des Vollgesangs tritt schon nach einer Woche Testosteronbehandlung auf. Auch bei diesen Versuchstieren kam es nach längerer Testosterongabe zu einer deutlichen Tourenverlängerung. Die Stabilität der Elemente innerhalb der Tour erreichte erst nach 30 bis 40 Tagen Werte des Vollgesangs. 3. Diskutiert wird der unterschiedliche Einfluß von Testosteron auf die verschiedenen Merkmalsebenen der Verhaltensorganisation: es steigert die Gesangsmotivation der Tiere; die Syntax des Vollgesangs wird durch die Hormongabe aktiviert; jung kastrierte Tiere, deren Gesangsontogenese durch die Kastration unterbrochen wurde, sind nicht sofort in der Lage, einen Gesang mit stabilen Elementen zu äußern. Testosteron löst die Differenzierung der gesangsrelevanten Hirnstrukturen (HVc, RA) aus, die erst nach einiger Zeit abgeschlossen ist.

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Both 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.

The relationship between the ontogenetic pattern of sex steroids and the differentiation of sexually dimorphic song in canaries of both sexes was studied. Songs were recorded to assess the temporal course of different developmental stages. Song parameters such as length and frequency of tours were measured. Parallel to behavioural observations, all birds were bled regularly every 2&30 days from the age of 15 days to day 235. The plasma samples were analyzed by RIA to measure testosterone (T), dihydrotestosterone (DHT) and estradiol-17P (El). The following results were obtained: 1) In young male canaries we distinguish three different stages of song development: subsong, starting at the age of 30 days, plastic song, and juvenile autumnal song finally giving way to the rigid and stable utterances of the reproductive period in next spring. During ontogeny the length and frequency of tours increase gradually. Female canaries were not observed singing regularly during their first year of life, whereas males sing very frequently. 2) Both sexes show tendencies to elevated titres of testosterone before the onset of juvenile moult. These titres correspond to those of paired males during the reproductive cycle. Song development is not correlated with the ontogenetic pattern of testosterone: the process of crystallization from the amorphic songs uttered by juveniles progresses gradually to the autumnal song in late autumn, when the titres of T in males are low (< 200 pg/ml). Female T and D H T levels during ontogeny correspond to those of the males. 3) There are sex differences in the estradiol pattern. Males show higher titres in several stages of development than females.

In the song control area HVc of the canary, intercellular dye‐coupling among astrocytes was studied by intracellular injection of neurobiotin into identified single astrocytes. Injection of individual astrocytes into acute slices resulted in dye spread to neighboring astrocytes, covering a sphere of up to 1 mm in diameter. The astrocytic nature of the dye‐coupled cells was verified by double labeling of neurobiotin‐filled cells with antisera for the astrocytic filament proteins GFAP or vimentin. The similarity in the number of dye‐coupled cells and the total number of astrocytes labeled by immunocytochemical markers indicate that dye‐coupling is specific for astrocytes and labels almost the entire local astrocytic population. Within the major nucleus for vocal control (HVc), approximately 25% more astroglial cells were present than in the surrounding forebrain tissue. There is no apparent hindrance of dye spread at the border of the HVc. The density of dye‐coupled astrocytes and the expression of cytoskeletal filament proteins differed markedly between the reproductive period in spring and the quiescent period in autumn. While vimentin is the major astroglial filament in autumn, GFAP is strongly expressed in spring. The density of dye‐coupled astrocytes reveals a marked increase in the reproductive period, followed by a reduction in autumn. The data indicate that the astrocytic population in the avian forebrain undergoes significant changes coincident with the known functional changes in the vocal control nuclei during periods of song production. GLIA 27:88–100, 1999. © 1999 Wiley‐Liss, Inc.

We studied human melody perception and production in a songbird in the light of current concepts from the cognitive neuroscience of music. Bullfinches are the species best known for learning melodies from human teachers. The study is based on the historical data of 15 bullfinches, raised by 3 different human tutors and studied later by Jürgen Nicolai (JN) in the period 1967-1975. These hand-raised bullfinches learned human folk melodies (sequences of 20-50 notes) accurately. The tutoring was interactive and variable, starting before fledging and JN continued it later throughout the birds' lives. All 15 bullfinches learned to sing alternately melody modules with JN (alternate singing). We focus on the aspects of note sequencing and timing studying song variability when singing the learned melody alone and the accuracy of listening-singing interactions during alternatively singing with JN by analyzing song recordings of 5 different males. The following results were obtained as follows: (1) Sequencing: The note sequence variability when singing alone suggests that the bullfinches retrieve the note sequence from the memory as different sets of note groups (=modules), as chunks (sensu Miller in Psychol Rev 63:81-87, 1956). (2) Auditory-motor interactions, the coupling of listening and singing the human melody: Alternate singing provides insights into the bird's brain melody processing from listening to the actually whistled part of the human melody by JN to the bird's own accurately singing the consecutive parts. We document how variable and correctly bullfinches and JN alternated in their singing the note sequences. Alternate singing demonstrates that melody-singing bullfinches did not only follow attentively the just whistled note contribution of the human by auditory feedback, but also could synchronously anticipate singing the consecutive part of the learned melody. These data suggest that both listening and singing may depend on a single learned human melody representation (=coupling between perception and production).

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