Armaments and ornaments in the rock sparrow: a possible dual utility of a carotenoid-based feather signal

Females often base their mating preferences on male sexual secondary traits that are used to settle contests among males. Such traits are likely to be honest indicators of male quality if they are constantly used during costly male–male agonistic interactions. Carotenoid signals have been shown to work as a handicap because they are costly to produce. However, the role of carotenoids as “honest” signals during male contests is less clear, and it is not known whether a carotenoid-based trait can serve in both male–male competition and female choice. In this study, we studied the dual function of a carotenoid feather ornament in the rock sparrow (Petronia petronia), a bird species in which both sexes have a yellow throat patch whose size positively correlates with phenotypic measures. First, we investigated, in a field study, whether the size of a male’s yellow patch correlates with his ability to acquire a territory. Second, we tested the signal function of the yellow patch in two male–male interaction in captivity experiments. Finally, we measured female preference for males differing in throat patch size in a mate choice experiment. Our experiments revealed that the size of a male’s throat patch positively correlated with the number of nest boxes he was able to defend. Moreover, in controlled conditions, males with relatively large yellow patches had earlier access to food than those with small patches. Also, in an experiment in which a dummy rock sparrow with an experimentally manipulated yellow patch was positioned near a feeder, latency to feed by focal birds positively correlated with dummy patch size. Lastly, in a dichotomous mate choice experiment, females showed a proximity preference for males whose patch was experimentally enlarged. Taken together, these results suggest that the same carotenoid feather signal may be used in both male–male competition and female choice in this passerine bird.     

Predation risk affects courtship and attractiveness of competing threespine stickleback males

The effect of predation risk and male-male competition on male courtship behaviour and attractiveness to females was studied in the threespine stickleback (Gasterosteus aculeatus) by presenting dummy or live females to solitary and competing males under different predation risks. In the presence of a predator, males decreased courtship activity. Different courtship components were, however, adjusted to different extents and in opposing directions to predation risk, probably because the single components may have varied in riskiness. The presence of a competing male decreased overall courtship activity, but increased the frequency of zigzags, suggesting zigzagging to be a competitive strategy against other males. In the presence of a predator male courtship activity was not affected by a competitor. Female mate choice correlated with the males' previous frequency of zigzags towards a dummy female. However, when a live female paid attention to a male, the male decreased zigzagging and instead increased leading and fanning behaviours, probably trying to attract the female to the nest to mate. Predation risk affected the attractiveness of males as females reduced their attention to a male when he faced a predator and reduced his courtship activity. As females instead increased their attention to a competing male that had increased his courtship activity, due to decreased competition, males clearly are balancing mating opportunities against predator avoidance. When males vary in their susceptibility to predators, predation risk may thus affect mating success of competing males. Received: 31 January 1997 / Accepted after revision: 15 April 1997     

Ordering effects and choice set awareness in repeat-response stated preference studies

We present an experiment designed to investigate the presence and nature of ordering effects within repeat-response stated preference (SP) studies. Our experiment takes the form of a large sample, full-factorial, discrete choice SP exercise investigating preferences for tap water quality improvements. Our study simultaneously investigates a variety of different forms of position-dependent and precedent-dependent ordering effect in preferences for attributes and options and in response randomness. We also examine whether advanced disclosure of the choice tasks impacts on the probability of exhibiting ordering effects of those different types. We analyze our data both non-parametrically and parametrically and find robust evidence for ordering effects. We also find that the patterns of order effect in respondents' preferences are significantly changed but not eradicated by the advanced disclosure of choice tasks a finding that offers insights into the choice behaviors underpinning order effects.     

Strategic male signalling effort in a desert-dwelling fish

Males often use elaborate courtship displays to attract females for mating. Much attention, in this regard, has been focused on trying to understand the causes and consequences of signal variation among males. Far less, by contrast, is known about within-individual variation in signal expression and, in particular, the extent to which males may be able to strategically adjust their signalling output to try to maximise their reproductive returns. Here, we experimentally investigated male courtship effort in a fish, the Australian desert goby, Chlamydogobius eremius. When offered a simultaneous choice between a large and a small female, male gobies spent significantly more time associating with, and courting, the former, probably because larger females are also more fecund. Male signalling patterns were also investigated under a sequential choice scenario, with females presented one at a time. When first offered a female, male courtship was not affected by female size. However, males adjusted their courtship effort towards a second female depending on the size of the female encountered previously. In particular, males that were first offered a large female significantly reduced their courtship effort when presented with a subsequent, smaller, female. Our findings suggest that males may be able to respond adaptively to differences in female quality, and strategically adjust their signalling effort accordingly.     

Male-male association patterns and female proximity in the guppy,Poecilia reticulata

If males differ in their ability to attract potential mates, and are able to perceive such differences, theory predicts they should distribute themselves in a manner that increases their probability of obtaining potential matings. The relationship between male-male association patterns and the proximity of females in social groups, however, remains virtually unexplored. Experimental analysis of this relationship in the guppy, Poecilia reticulata, demonstrates that in preference tests males showed a strong tendency to associate with other males that were further away from potential mates than they were themselves. Male guppies pursue a behavioral strategy that involves categorizing other males based on their proximity (and possibly relative attractiveness) to females, remembering the identity of such individuals, and using this information when choosing between other males as associates. Such a strategy may increase a male's chances of being the individual chosen by a female assessing nearby males.     

Factors Determining the Choice of Hunting and Trading Bushmeat in the Kilombero Valley,Tanzania

Regulation of illegal bushmeat trade is a major conservation challenge in Africa. We investigated what factors are most likely to induce actors in the bushmeat trade to shift to an alternative occupation by conducting a choice experiment with 325 actors in the bushmeat trade in the Kilombero Valley, Tanzania. Specifically, we asked respondents to choose between hunting or trading bushmeat and alternative salary‐paying work, in a set of hypothetical scenarios where the attributes of these alternatives were varied and included measures of command and control, price of substitute meat, daily salary in the work option, and whether or not cows were donated to the respondent. We modeled the choice contingent on socioeconomic characteristics. The magnitude of fines and patrolling frequency had a significant but very low negative effect on the probability of choosing to engage in hunting or trading bushmeat compared with the salary of an alternative occupation. Donation of livestock and the price of substitute meats in the local market both affected the choice significantly in a negative and a positive direction, respectively. The wealthier a household was the more likely the respondent was to choose to continue hunting or trading bushmeat. On the margin, our results suggest that given current conditions in the Kilombero Valley on any given day 90% of the respondents would choose salary work at US$3.37/day over their activities in the bushmeat trade, all else equal. Factores que Determinan la Elección de Cazar y Vender Carne de Caza en el Valle Kilombero, Tanzania     

Fluctuating asymmetry and sperm transfer in male decorated field crickets (Gryllodes sigillatus)

Fluctuating asymmetry (FA) in limb size in female decorated field crickets (Gryllodes sigillatus) was associated with a reduction in the size of the spermatophore and the amount of sperm transferred by males and an increase in the time taken to transfer a spermatophore following introduction of a female. There was a weaker negative relationship between limb asymmetry in males and sperm number but no significant relationship between asymmetry in either sex and spermatophylax size. In line with a previous study, female size did not appear to influence spermatophore production or mating decisions by males. The results imply that developmental instability affects both gamete production and mating decisions among males, although the relationships between spermatophore size, sperm number and asymmetry in females are unlikely to be the result of males perceiving differences in female FA. Received: 24 July 1999 / Received in revised form: 22 November 1999 / Accepted: 31 December 1999     

Mate choice in the brown thornbill (<Emphasis Type="Italic">Acanthiza pusilla</Emphasis>): are settlement decisions,divorce and extrapair mating complementary strategies?

In socially monogamous birds, females may express mate preferences when they first select a breeding partner, through divorce and subsequent breeding dispersal to a new partner and through extrapair mating. We examined settlement patterns, divorce and breeding dispersal in a sedentary Australian passerine, the brown thornbill (Acanthiza pusilla), in relation to two traits known to influence extrapair paternity (male age and male size). Settlement decisions, divorce and territory switching behaviour were all female strategies that reduced their likelihood of breeding with 1-year-old males. Females preferred to settle in territories with 2+ -year-old males, were more likely to divorce 1-year-old males, and only switched territories if they had an opportunity to form a new pair bond with an old male. In contrast, female settlement and divorce decisions were not influenced by male size. Female thornbills obtain a direct benefit from preferring older males as social mates because breeding success improves with male age in brown thornbills. Nevertheless, divorce rates in this species were low (14% of pair bonds were terminated by divorce), and individuals rarely switched territories following the death of a mate. Both of these mating strategies appeared to be primarily constrained by the distance adults moved to initiate a new pair bond (1–2 territories) and by the limited availability of unpaired older males in the immediate neighbourhood.Communicated by M. Webster     

Local adaptation and sexual selection: a reciprocal transfer experiment with the grasshopper Chorthippus biguttulus

Immigration into locally adapted populations has been suggested, among other potential causes, to maintain genetic variance in fitness necessary for good-genes models. Using a reciprocal transplant experiment we examined whether females prefer native to transferred males in the grasshopper Chorthippus biguttulus. On average, native and transferred males did not differ in their attractiveness, measured as female response rate to playbacks of male acoustic courtship signals. In line with this result, we found no significant effect of transfer on body size, condition, fluctuating asymmetry or song traits. However, the reciprocal transplant experiment showed that environmental conditions did influence body condition and maximum loudness of the calling song, but that the genetic origin of male grasshoppers had no significant effect on any of the analysed traits.Communicated by L. Simmons     

Mate choice in the yellow-shouldered widowbird: correlates of male attractiveness

Recent investigations of male ornaments in sexual selection have used experimental manipulation of tail length in three widowbird species, but only for one of these have correlates of male reproductive success been reported. I examined correlates of male attractiveness to nesting females over two breeding seasons for the polygynous yellow-shouldered widowbird, Euplectes macrourus, in order to discover which cues females may be using to select mates. The black, long-tailed ( 10 cm) males defend large territories and build nest frames, or cock's nests, which females then line and use for nesting. I examined various aspects of male morphology, five behavioral displays, territory characteristics, and the number of cock's nests that males built. Few correlates of mating success were found. The best predictor was the number of cock's nests that a male builds, though one courtship display also correlated with male mating success in 1 year, as did average grass height. Tail length did not correlate with male mating success. A partial correlation analysis confirmed that cock's nests and, in 1 year, grass height, were the primary contributers to male success. Females may choose where to nest primarily on the availability of suitable nesting sites. Long tails may be used by females seeking extra-pair copulations or in male-male competition for territories.