Female pied flycatchers Ficedula hypoleuca choose male characteristics in homogeneous habitats

Summary The paper reports the results of a 2-year study of pairing success of male pied flycatchers in a homogeneous habitat. A handicapping experiment was carried out in which certain wing and tail feathers were removed from randomly selected males. Handicapped males had reduced pairing success, they lost weight, and they sang less frequently than control males. Male pairing success was positively correlated with the darkness of the plumage, body-size, and previous breeding experience. Earlier studies on the same species have failed to detect any relationships between pairing success and male characteristics, possibly because of habitat heterogeneity and variation in nest site quality. The evolutionary basis for female choice of male characteristics is discussed. There are reports that males with attractive traits (e.g. black plumage) provide a high quality of parental care. However, the fact that male pairing success was related to male conspicuousness makes it difficult to discriminate between active and passive female choice.     

Female nutritional state affects the rate of male incubation feeding in the pied flycatcher Ficedula hypoleuca

Summary Male pied flycatches Ficedula hypoleuca regularly feed their mates during incubation. By experimentally supplying some females with extra food we studied how the female's nutritional state affected her incubation schedule and the rate at which her mate fed her. Females that received extra food spent more time on the nest and shorter periods away from it, compared with control females. This suggests that nest attentiveness is governed by the amount of energy available to the female. When females reccived extra food, males decreased their rate of incubation feeding. They also did so in response to increasing ambient temperatures, whereas incubation schedules were unaffected. We, therefore, conclude that our results support the female nutrition hypothesis, i.e., that the food provided by the male constitutes a significant nutritional contribution to the incubating female.     

Female mate choice determines reproductive isolation between sympatric butterflies

Animal courtship rituals are important for species recognition, and a variety of cues might be utilized to recognize conspecific mates. In this paper, we investigate different species-recognition mechanisms between two sympatric butterfly sister species: the wood white (Leptidea sinapis) and Real’s wood white (Leptidea reali). We show that males of both species frequently court heterospecific females both under laboratory and field conditions. The long-lasting elaborate courtships impose energetic costs, since the second courtship of males that were introduced to two subsequent conspecific females lasted on average only one fourth as long as the first courtship. In this paper, we demonstrate that premating reproductive isolation is dependent on female unwillingness to accept heterospecific mates. We studied female and male courtship behavior, chemical signaling, and the morphology of the sexually dimorphic antennae, one of the few male traits visible for females during courtship. We found no differences in ultraviolet (UV) reflectance and only small differences in longer wavelengths and brightness, significant between-species differences, but strongly overlapping distributions of male L. sinapis and L. reali antennal morphology and chemical signals and minor differences in courtship behavior. The lack of clear-cut between-species differences further explains the lack of male species recognition, and the overall similarity might have caused the long-lasting elaborate courtships, if females need prolonged male courtships to distinguish between con- and heterospecific suitors.     

Female mate choice in the non-territorial lizard Ameiva plei (Teiidae)

Mate choice by females has been documented in a variety of taxa. Female mate choice in species lacking male resource control or paternal care might occur if preferred males provide protection from harassment. Female mate choice was investigated in a natural population of the non-territorial lizard Ameiva plei (Teiidae). Consort pairs were allowed to form naturally. Consort males were significantly larger than non-consort males. After removal of consort males, the “abandoned” female's reaction to the first male who approached her was recorded. Females rejected all small males. Female preference for large males was significantly higher than preference for small males. Large males may be better equipped to guard the females from harassment and behavior of large males is less harassing than behavior of small males, thereby affording the female increased foraging time. Received: 21 June 1996 / Accepted after revision: 28 December 1996     

Begging affects parental effort in the pied flycatcher, Ficedula hypoleuca

It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term effects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied flycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex difference in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its effort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour. Received: 24 January 1997 / Accepted after revision: 30 August 1997     

Mate retention and male polyterritoriality in the pied flycatcher Ficedula hypoleuca

Summary We studied pair bond maintenance in the pied flycatcher in an experiment on nest predation at the incubation stage. Males defending one or more additional nestboxes (i.e. polyterritorial) on the day of nest predation were significantly more successful in retaining their mate than were the monoterritorial males (54% and 13% succeed, respectively). We manipulated the number of nest sites available for renesting, and found that the females remained preferentially with those males that had access to a new site, regardless of the previous territorial status of the male. Thus, the success of the polyterritorial males in mate retention was related primarily to the resource defended (a new nest site) rather than to some quality of the particular males per se. When the females could choose between alternative nestboxes for renesting, they selected the one located at the greatest distance from the initial site (Fig. 1). Male polyterritorial behaviour has previously been interpreted as a means of achieving polygyny. Our results show that this behaviour may be advantageous even in the absence of polygyny, especially at high levels of nest predation.     

Female mate selection in the natterjack toad: active choice or passive atraction?

Summary Variation in seasonal mating success among male natterjack toads (Bufo calamita) was influenced by the number of nights that males spent at the pond and by male body size. Large males produced louder and lower frequency calls than small males, and maintained larger acoustic territories. After arriving at the pond, one half of all observed females mated with the first male they encountered. The remainder visited several males before initiating amplexus, but no criteria could be identified that females might have used when deciding whether to accept or reject a male. Movements between several males seem to be best explained by low female responsiveness to male advertisement calls on cold nights which were nonoptimal for oviposition. Females attempted to reject non-calling males both before and after amplexus, but this may be a mechanism to avoid mismating with males of the common toad (Bufo bufo), an explosive breeder that utilised the same pond. In two-choice playback experiments using synthetic advertisement calls, females showed no preference for calls based on their frequency. Females preferred calls of intermediate pulse repetition rate equivalent to those produced by a male at the same body temperature. Pulse rate is thus potentially subject to stabilishing selection and may be an important character for species-recognition. Females preferred fast rather than slow call rates, but only when the alternative rates were extreme. They also preferred calls which they perceived at the highest sound pressure level, but did not discriminate between absolute sound pressure levels of alternative stimuli at different distances. Since females that delay mating and oviposition may suffer predation, it is suggested that female preference for loud, rapidly repeated calls may be adaptive in the sense of minimizing the costs of locating conspecific males, rather than maximizing the probability of obtaining a high quality mate. Competition between males to maintain large acoustic territories and produce calls that can be easily detected by females would seem to be a sufficient mechanism to explain the evolution of the striking calls produced by male natterjacks.     

Female mate choice in the gray treefrog (Hyla versicolor) in three experimental environments

We studied female mate choice by Hyla versicolor in three venues to examine how acoustic and spatial complexity, background noise, and the calling behavior of males might influence preferences manifest in previous laboratory two-stimulus choice tests. Our laboratory-based two-stimulus choice tests with and without broadcasts of chorus noise demonstrated that females prefer long calls relative to short calls when calling efforts of alternatives are equivalent. Background noise impaired the ability of females to discriminate in favor of longer over shorter calls, but the magnitude of the effect was small. Captures of females at eight speakers broadcasting 6- to 27-pulse calls at the edge of a pond revealed strong discrimination against only the shortest call variant. In natural choruses, females may only rarely encounter males using such unattractive vocalizations. Female phonotaxis at an artificial pond with caged and electronically monitored calling males also indicated that consequences of female preferences for temporal aspects of calling observed in two-stimulus choice tests are much attenuated in choruses and explain only small portions (<10%) of the variation in male mating success. Nevertheless, relatively high call duration and calling effort increased male attractiveness. Acoustic interference emerged as another significant factor influencing male mating success and possibly the differences in female choice observed in laboratory and chorus settings. We suggest that the bias of females against both overlapped and very short calls may help explain why males lengthen their calls but lower their rate of delivery in response to increases in chorus size.     

Reproductive success of monogamous and polygynous pied flycatchers (Ficedula hypoleuca)

One of the most interesting aspects of the mating system of pied flycatchers is the regular occurrence of polygyny. Here we present data on the reproductive success of polygynously paired pied flycatcher males compared to monogamous males based on paternity analyses through DNA fingerprinting. Males paired with two females suffered a higher loss in reproductive output per female compared to monogamous males due to (1) a greater proportion of unhatched eggs in their broods, (2) greater nestling mortality and (3) a greater probability of being cuckolded. Nevertheless, the number of fledglings was significantly greater for polygynous males. Based on the number of nestlings that returned for subsequent breeding seasons, however, the reproductive success of monogamous and polygynous males did not differ significantly. These data raise the question as to why males attempt polygyny. Received: 16 August 1999 / Received in revised form: 15 March 2000 / Accepted: 18 March 2000     

Female mate choice,male migration,and the threat of infanticide in ringtailed lemurs

Summary Paternity determination by DNA fingerprinting is reported for a long-term study group of semi-free-ranging ringtailed lemurs (Lemur catta), together with behavioral data collected independently. In 1985, fraternal twin males unfamiliar and unrelated to the resident ringtailed lemurs were introduced to the forest enclosure. Every mature resident male attacked the immigrants frequently across the next 5 months, whereas no female ever did. All observed estrous females showed sexual proceptivity toward the' immigrant males; three solicited copulation exclusively from them. Each female repelled sons, matrilineal brothers, and other resident males from attempting to copulate. Over a 5-year period, four of five females always reproduced with distantly related or unrelated males (Fig. 3). Despite low dominance status throughout the case study, an immigrant sired the off-spring of each female that was proceptive toward only the immigrants, demonstrating that female choice can override male dominance relations to determine reproductive success among male ringtailed lemurs. In the birth season following the 1985–1986 immigration, each of four females targeted one or two particular adult males for consistent attack across the period of infant dependency, beginning days after parturition. Paternity determinations, colony records, and subsequent study of two groups allowed 66 cases of this mode of maternal aggression to be documented. In each, the targeted male had not fathered the protected infant, and almost invariably, he was unrelated to the infant's mother. New mothers attacked every male that immigrated following their infants' conceptions and a few familiar males with whom they had not been seen to copulate during the previous breeding season. Recent attempts by immigrant males to kill infants confirmed the anti-infanticidal function of maternal targeting of males. All results were interpreted together to advance a prospective model of the mating system of ringtailed lemurs. Female avoidance of incest has led to the evolution of natal male dispersal. Subsequently, males should prefer to transfer into groups containing few and/or status-vulnerable males. We predict that, by killing others' infants, males simultaneously increase chances for success in females' next reproductive efforts and terminate current fathers' reproductive eligibility in a group. Basic hypotheses that await testing are that (a) raising an infant through weaning reduces a female's chances for reproductive success the following year and (b) males that demonstrate the capacity to promote the survival of infant offspring are most attractive to females as mates.     

Long-lasting effects of yolk androgens on phenotype in the pied flycatcher (Ficedula hypoleuca)

The hormonal environment during early development, such as maternally derived androgens in bird eggs, shapes the development of the offspring in ways that may have important long-term consequences for phenotype and behavior and, ultimately, fitness. We studied the long-term effects of yolk androgens on several phenotypic and physiological traits in male and female pied flycatchers (Ficedula hypoleuca) by experimentally elevating yolk androgen levels and rearing birds in common-garden environment in captivity. We found that high yolk androgen levels increased the basal metabolic rates in both females and males in adulthood. High yolk androgen levels did not affect male melanin coloration or plumage ornaments, or timing or speed of moult in either sex. No effect of androgen treatment on cell-mediated or humoral immune response was found in either sex. Covariation among the measured phenotypic traits was further not altered by androgen treatment. Our results suggest that exposure to high androgen levels can have long-lasting effects on some offspring traits, but do not seem to lead to different phenotypes. Furthermore, the role of yolk androgens affecting sexually selected male traits in our study species seems to be minor. The fitness consequences of yolk androgen-induced higher metabolic rates remain to be studied.     

Orientation of the pied flycatcher Ficedula hypoleuca: cue-conflict experiments during spring migration

Hierarchical relationships among different compass systems in long-distance migrants are still a matter for discussion because different studies have led to highly variable and apparently contradictory results. We carried out cue-conflict experiments during spring migration on pied flycatchers Ficedula hypoleuca (Passeriformes, Muscicapidae). Birds were exposed to a conflict between celestial and magnetic information by altering the polarized light pattern or magnetic field. The polarization pattern was shifted (±90°) with filters, whereas the magnetic field was altered (+90°) through Helmholtz coils. Birds were tested in modified Emlen funnels both before and after the cue conflict; during the tests, only the natural magnetic field was available. This protocol was designed to test whether the experimental birds recalibrated their magnetic compass on the directional information derived from the light polarization pattern when the region near the horizon was visible during the conflict. Contrary to this expectation, we did not record any significant shift in magnetic orientation after one or repeated exposures to the cue conflict. Our results support earlier studies, which suggest that the magnetic field is the primary compass cue during the migratory period.     

Mate fidelity of renesting pied flycatchers Ficedula hypoleuca in relation to characteristics of the pair mates

Summary After a nesting failure, individual pied flycatchers may renest with the same or a new partner. In a 2-year study, carried out in a homogeneous habitat, we removed the clutches of a total of 124 monogamous pairs to study mate fidelity. The chance of a male obtaining a new partner if the pair bond had been broken was very low, so it would be in a male's interest to retain his original mate. Females in good condition showed a greater tendency to break the pair bond, and moved longer distances for renesting, than females in poor condition. Females that had nested in the area in a previous year were more site-tenacious, though not significantly more faithful to their mates, than those that were nesting in the area for the first time. Males that succeeded in retaining their mate were characterized primarily by having black plumage, and males from which certain feathers had been removed (=handicapped) tended to lose their mates. Females preferred the same male characteristics when they chose their mates in early spring. Hence, the decision about mate fidelity is influenced by the condition of the female and the attractiveness of her mate. Some evidence was found that male parental quality was correlated with male attractiveness.     

Female mate choice in the zebra finch — the effect of male beak colour and male song

Studies of female mate preference in zebra finches (Taenopygia guttata) have shown that male beak colour and song rate are important. However, the two characters are correlated. Here the effect of beak colour and song rate on female choice are examined independently. In mate choice tests involving two males, beak colour was manipulated artificially using nail varnish. The results showed that females showed a significant preference for males with a high song rate, but not with a red beak. Females did not prefer males with a red beak if song rate was low and females preferred males with orange beaks who expressed a high song rate. Female preference for males with red beaks was not found when beak and song characters were no longer correlated.     

Copying and the repeatability of mate choice

Models of sexual selection by female choice require heritable variation in female mating preferences in order for sexual selection to operate. However, recent theoretical work shows that female preferences which are transmitted non-genetically can result in exaggeration of male ornamentation. Guppies exhibit both mate copying and considerable heritable variation in female preferences. I studied the importance of these phenomena by measuring repeatability of female mate choice, which acts as an estimate of the upper limit to which a feature may be heritable, and the incidence of mate choice reversal in paired-trial binary mate choice experiments. Mate choice was significantly repeatable except in the treatment where females were given the opportunity to copy a female that contradicted their original choice. Apart from this, I found no evidence that females copy the mate choice of others. The differences between males in ornamentation had no effect on the consistency of female mate choice or the probability that they would reverse their original choice decision (in both controls and the copying experiment). The interval between choice trials did not influence repeatability significantly, indicating that the independence of choice decisions is not related to the time interval between them. Received: 9 February 1996/Accepted after revision: 6 July 1996     

Parasite load predicts mate choice in guppies

Summary The influence of parasites on mate selection and on a secondary sexual character was studied in guppies (Poecilia reticulata). In fish infected with Camallanus cotti or Gyrodactylus, females were found to prefer males with relatively few parasites, and this preference was associated with a higher display rate in less parasitised males.     

Family structure influences mate choice in white-fronted bee-eaters

White-fronted bee-eaters live in patrilocal, extended family groups in which several pairs may breed simultaneously and in which helping behavior by nonbreeders is common. The composition of a male's family, and his social position within it, are major predictors of his expected reproductive success. For females, the dispersing sex, a decision to pair necessitates forfeiting any potential fitness benefits available through helping in her family, in favor of the potential benefits of breeding in the male's family. Using a set of equations that incorporate the social and non-social predictors of nesting success, we develop a payoff matrix for the expected fitness (current and future) of pairing with different categories of males. Predictions generated from this payoff matrix were supported by data: (1) Females that could help close kin (and thus garner large indirect benefits) tended to remain unpaired. (2) Males with social characteristics associated with low expected reproductive success were more often rejected as potential mates by females. (3) High-quality males, those with potential helpers of their own, were nearly always paired. Simulation analyses were used to investigate female pairing decisions in more detail, and to test various hypotheses about possible decision rules. We demonstrate that pairing females incorporate an assessment of the family structure of potential partners into their mate choice decisions. Such social characters represent an aspect of female choice that has been underappreciated. We suggest that social characters will prove to be important components of mate choice decisions in many species where kinship and dominance considerations influence the likelihood, or success, of breeding.     

Bigamy and mate choice in the biparental cichlid fish Cichlasoma nigrofasciatum

Summary Sixty percent of C. nigrofasciatum males showed bigamous behaviour when held in small, outdoor ponds at an adult sex ratio of 5 males to 10 females. No male held more than two pair bonds simultaneously. Bigamy had reproductive benefits; bigamous males, on average, fathered more broods that survived well into the free-swimming fry stage than did monogamous males. In ponds where adult size varied, no positive correlations were found, for either sex, between adult size and frequency of spawning or success of broodrearing, despite predictions that larger size would confer reproductive benefits on both sexes. A significant positive correlation was found between the sizes of mated individuals in the pond where both sexes varied in size. On theoretical grounds this relationship is likely to be more strongly influenced by female than by male choice of spawning partner.