Experimental determination of a unit of song production in the zebra finch (Taeniopygia guttata).

Zebra finch (Taeniopygia guttata) song is composed of syllables delivered in a set order. Little is known about the program that controls this temporal delivery. A decision to sing or not to sing may or may not affect the entire song.

Steroid Modulation of Muscarinic Cholinergic and alpha2-Adrenergic Receptor Density in the Nucleus Intercollicularis of the Japanese Quail.

Androgen modulation of neurotransmitter receptor density was investigated in the nucleus intercollicularis (ICo) of male and female Japanese quail (Coturnix coturnix japonica). ICo appears to play an important role in the neural control of testosterone (T) dependent vocal behaviour. Two receptor types were investigated in this nucleus; muscarinic cholinergic receptors, labelled using [3H]N-methyl scopolamine (NMS) as the ligand, and alpha2-adrenergic receptors, labelled using [3H]p-amino-clonidine (PAC) as the ligand.

Testosterone induction of song in photosensitive and photorefractory male sparrows.

Song in male songbirds is activated by the sex steroid testosterone (T). Using male song sparrows (Melospiza melodia), we compared effects of T in the normal spring state of photosensitivity (i.e.

Timbre control in zebra finch (Taeniopygia guttata) song syllables.

Zebra finch (Taeniopygia guttata) song syllables often include harmonically related frequency components. These harmonics may be suppressed, and this differential emphasis varies between the syllables in a song and between individual birds' songs. These patterns of harmonic suppression are timbre.

Distribution of alpha 2-adrenergic receptors in the brain of the Japanese quail as determined by quantitative autoradiography: implications for the control of sexually dimorphic reproductive processes.

With the use of [3H]p-aminoclonidine (PAC), alpha 2-adrenergic binding sites were mapped in the brain of the Japanese quail (Coturnix coturnix japonica). The sites were labeled with the use of in vitro quantitative autoradiography. Special attention was given to areas implicated in the control of sexually dimorphic reproductive processes including sexual behavior.

Immunohistochemical localization of corticotropin-releasing factor in selected brain areas of the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia).

Corticotropin-releasing factor (CRF) was localized in the brains of two passerine species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), by means of immunohistochemistry. The hypothalamic distribution of this peptide in these species includes a complex of immunoreactive perikarya observed in the paraventricular nucleus (PVN), in both its medial and lateral divisions. Nerve fibers were also seen running from these areas to the anterior median eminence (AME) where a terminal field is apparent.

Testosterone and survival: a cost of aggressiveness?

Free-living male brown-headed cowbirds were captured during the breeding season, implanted with testosterone-filled Silastic tubing, and released. Radioimmunoassay verified that the implants maintained circulating plasma testosterone values at maximal breeding season levels well beyond the normal time of decline. Survival to the following year of these implanted males was compared with survival of unimplanted birds captured in other years, and also with survival of males given empty implants.

Orangutan activity budgets: Monthly variations and the effects of body size, parturition, and sociality.

The activity budgets of individual orangutans were investigated at the Kutai Reserve, Indonesia. Activity profiles within and between individuals were compared to examine monthly variations in feeding patterns, potential energetic constraints imposed by large body size and parturition, and the costs of sociality. Animals showed monthly changes in travelling, feeding, and resting patterns.

The role of sex steroids in the acquisition and production of birdsong.

Male birdsong is generally regarded as a secondary sexual characteristic under the control of gonadal steroids. Song typically waxes and wanes with the seasonal cycle of testicular growth and regression and decreases after adult castration. Testosterone therapy reinstates song, induces it in females, augments it in intact males, and spring testosterone profiles correlate with seasonal song production.

Alarm signals in birds: the role of testosterone.

In the laboratory and under semi-naturalistic conditions, male domestic fowl (Gallus gallus) produce more alarm calls in response to predatory birds flying overhead than females. This study tests the hypothesis that testosterone is a factor in the control of aerial alarm call production. Birds were castrated early in life and tested as adults in the laboratory.

Audience effects on alarm calling in chickens (Gallus gallus).

The male domestic chicken (Gallus gallus) has been found to modulate the production of vocal signals in response to the presence or absence of a suitable audience. We investigated effects on alarm calling by presenting overhead predator models to cockerels in the presence of a variety of social companions. The production of aerial predator calls in response to hawk silhouettes varied with the presence or absence of a member of the same species.

Bird song syntax: learned intraspecific variation is meaningful.

Song syntax, defined as orderly temporal arrangements of acoustic units within a bird song, is a conspicuous feature of the songs of many species of passerine birds. While syntactical features play a role in interspecific song recognition by males of many bird species, syntax variation within species and female responsiveness to song syntax have received little attention. This report demonstrates that differences in naturally occurring learned song syntax within a species whose syntax varies geographically are behaviorally salient to both male and female birds.

Immunohistochemical localization of neuropeptides in the vocal control regions of two songbird species.

Immunohistochemistry was used to map the distribution of four neuropeptides in song control regions of two songbird species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia). We searched for positively stained cell bodies or apparent terminals containing vasoactive intestinal peptide (VIP), methionine-enkephalin (MET), cholecystokinin (CCK), and substance P (SUB P). Intraventricular colchicine pretreatment was administered to enhance the visualization of peptide-containing cell bodies.