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Competing for food by altricial and semiprecocial bird nestlings is a behaviour well known for its sensitivity to maternal androgens during prenatal development. Whether a similar effect is present in precocial species that do not beg is less well known. We therefore increased yolk testosterone levels within the physiological range at the onset of incubation to study its effects on food competition behaviour in the domestic chicken, Gallus gallus domesticus. We found an increase in competitiveness in testosterone-treated male domestic chicks, raising their level to that of the females. This is in line with the decrease in circulating plasma levels of males in the direction of the levels in females, and the overall decrease in androgen receptor densities after prenatal treatment as found previously. Hormones are known to have long-lasting organizing effects on behaviour and to affect sexual differentiation in vertebrates. Although research into hormone-mediated maternal effects has been productive, only a few studies describe (the ambiguous) effects into adulthood. Therefore we followed our animals into adulthood and recorded androgen-dependent social behaviour and secondary sexual characteristics, body mass and circulating plasma testosterone levels and checked whether these variables were treatment dependent. Treatment had a near significant effect on comb colour (both brightness and chroma). Again treatment caused a shift towards a more female-like phenotype. This suggests that, in contrast to earlier suggestions, maternal androgens may interact with (but not disrupt) sexual differentiation of brain and behaviour and the development of secondary sexual characteristics. (C) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

In previous mate choice experiments, female red jungle fowl, Gallus gallus, preferred males with long, bright red combs, red eyes, and (in one case) long tail feathers. When the colour and/or length of the comb was manipulated experimentally by placing artificial Latex combs over the natural ones, hens seemed to ignore the manipulated character and focused instead on traits such as hackle feather colour that had been secondary in importance in previous mate choice tests conducted with unmanipulated birds, but not as much so as the comb or eye characters. Similar results were obtained when tail length was experimentally lengthened or shortened. Rather than using only one or two traits as criteria of choice, females may rely on an additive or redundant suite of characters, with each providing part of the information used in making mate choice decisions.

Ornamental traits related to success in male-male competition were studied in red jungle fowl, Gallus gallus. In controlled fights between pairs of males, comb size was the only morphological trait that correlated with winning. Among free-ranging, socially integrated groups of 1-year-old males, body size and comb chroma (degree of saturation with pigment), in addition to comb size, were significantly related to dominance. In jungle fowl, the comb is strongly affected by blood testosterone level, which in turn reflects the current physical condition of the individual.

Agonistic postures of red jungle fowl hens were studied during initial pair encounters using time and motion analysis of motion picture films. Postures of each hen were quantitatively determined by measuring the angles of the trunk, neck and tail to the horizontal. The neck angle showed highly significant differences (P

Summary o 1. A study was made, using banded individuals, of the social organization and mobility in an unconfined population of Red Jungle Fowl (Gallus gallus) on the 100 acre grounds of the San Diego Zoo, California. The peak of breeding comes in April and May with very little breeding in December and January. 2. The different flocks of jungle fowl showed extreme locality fixation with small home ranges and territories centring about the flock roosting sites. The birds were generally within canyons and below the mesas. There is a peck order within these unconfined flocks, with dominant cocks associating with one to several hens, while subordinate cocks are frequently kept away from the hens. 3. Three birds transplanted over 1000–1400 ft showed no sign of any homing ability. 4. Young of the year generally stay at or near the home roost. Some of them move a short distance to peripheral and adjacent roosts and may help form new roosts along with adult males evicted from their home roosts by more dominant cocks. 5. There was a rapid turnover in this apparently protected population, and only about one bird in six that was old enough to be independent of its parents survived each year. After 3 years most of the roosting flocks were composed almost entirely of different birds, but there was little change in roosting sites.

The ability to respond promptly to a stimulus presented for the first time is a valuable asset for a precocial organism. Although the responses they give do not correspond perfectly with those elicited in the wild, parentally naive red jungle fowl chicks are able to discriminate between maternal feeding and distress calls. Discrimination is observable on the basis of differential vocalization and gross movement patterns. The feeding call elicits cessation of calling and locomotion, whereas the distress call promotes sustained vocalization and an increased amount of locomotor activity. Expression of the complete response to each call probably depends upon presence of appropriate visual and auditory stimuli. Comparison of responses given by feeding call-trained chicks and distress call-trained chicks indicates that vocal responding is probably affected by training experience. Orientation of the chick with respect to the position of the sound source is not consistent under either of the stimulus conditions.