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The "Challenge Hypothesis": Theoretical Implications for Patterns of Testosterone Secretion, Mating Systems, and Breeding Strategies
A combination of field and laboratory investigations has revealed that the temporal patterns of testosterone (T) levels in blood can vary markedly among populations and individuals, and even within… Expand
Testosterone and Aggression in Birds
The familiar spring sound of birdsongs heralds the onset of territory formation and a complex sequence of interrelated events that make up the breeding period. Such songs are an integral part of the… Expand
Hormones, developmental plasticity and adaptation
Phenotypic plasticity is the extent to which an organism can change its physiology, behaviour, morphology and/or development in response to environmental cues. Environmentally induced differences in… Expand
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 steroids1,2. Song typically waxes and wanes with the seasonal cycle of testicular growth and… Expand
Vocal communication in the domestic chicken: II. Is a sender sensitive to the presence and nature of a receiver?
Abstract As a test of the automaticity of the food calling behaviour of cockerels, their sensitivity to the presence and nature of an audience was explored. Males were presented with either a highly… Expand
Vocal communication in the domestic chicken: I. Does a sender communicate information about the quality of a food referent to a receiver?
Abstract Male domestic chickens produce ‘food calls’, when they are presented with food. Experiments, conducted under controlled conditions, on the responses of cockerels to the presentation of… Expand
Sex determination of Red‐tailed Hawks (Buteo jamaicensis calurus) using DNA analysis and morphometrics
ABSTRACT Currently, the sex of Red-tailed hawks (Buteo jamaicensis) cannot be determined by in-hand methods. Males and females do not differ in plumage and overlap in size. We collected feather… Expand
Testosterone and survival: A cost of aggressiveness?
- A. Dufty
- Biology, Medicine
- Hormones and Behavior
- 1 June 1989
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… Expand
Movements and Activities of Radio-Tracked Brown-Headed Cowbirds
- A. Dufty
- 1 April 1982
VARIATION IN THE STABLE-HYDROGEN ISOTOPE COMPOSITION OF NORTHERN GOSHAWK FEATHERS: RELEVANCE TO THE STUDY OF MIGRATORY ORIGINS
Abstract The analysis of stable-hydrogen isotope ratios in feathers (δDf) allows researchers to investigate avian movements and distributions to an extent never before possible. Nonetheless, natural… Expand