Female mate choice,male-male competition and parental care in the river bullhead,Cottus gobio L. (Pisces,Cottidae)

Male body size was tested for its influence on female mate choice, male-male competition and ability to defend broods in the river bullhead, Cottus gobio L., a polygynous fish with paternal care. Females presented with two potential mates of different sizes significantly preferred to spawn with the larger male. Males smaller than, or 1·5 times longer than, the female were rarely selected as mates. Larger males were more successful in defending their brood from conspecifics, which may explain female preference for them. Unmated large males displaced smaller guarding males from their nests and retained the acquired egg masses. Competition between males for nest sites with eggs can be accounted for by the preference of females for males already guarding eggs: by seizing a nest containing egg masses, a male will increase his chance of being chosen.     

Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)

The sand goby, Pomatoschistus minutus , was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male-male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non-random mating success in male P. minutus.     

Provisioning behaviour at the nest in single-parent versus biparental nests and male versus female parents in the common redstart (<Emphasis Type="Italic">Phoenicurus phoenicurus</Emphasis>)

We analysed video-sequences of undisturbed parental provisioning behaviour on 12 nests of common redstart (Phoenicurus phoenicurus). In 4 of the 12 nests, chicks were fed by a single parent only. We compared provisioning rate of chicks, time spent on the nest and food allocation rules between nests with uniparental and biparental care and between male and female parents in biparental nests. In nests with a single parent, the frequency of feeding visits per parent was higher than in biparental nests. As a result, the rate of food provisioning of chicks was similar in uniparental and biparental nests. The food allocation rules did not differ between uniparental and biparental nests. In biparental nests, male and female provisioning behaviour was similar though with two exceptions: males had a strong preference for feeding chicks in front positions in the nest and females spent a longer time on the nest after feeding. We conclude that single common redstart parents are able to compensate fully for the absence of the other parent through increased provisioning efforts, and that in biparental nests, males and females contribute equally to the provisioning of the young.     

Age of the incubating parents affects nestling survival: an experimental study of the herring gull Larus argentatus

The quality of conditions provided by avian parents will have consequences for both parental and offspring fitness. While many components of avian reproduction appear to vary with parental age, the effect of age on incubation has largely been ignored so far. In this study, we tested whether young herring gulls provide a different incubation environment from mature ones and whether this has consequences for offspring performance. Laying and rearing conditions were standardised using a cross-fostering protocol. Egg predation rates tended to be higher in the nests of young parents. However, nest site, nest construction and egg temperature during incubation did not vary with parental age. Overall, the duration of incubation was shorter in young compared to mature birds and this reflected the later laying date of the former, since incubation duration generally decreased across the season. However, male eggs incubated by young parents had longer incubation periods than predicted for their laying dates. In contrast, incubation length of female eggs incubated by young pairs, and of male and female eggs incubated by mature birds did not deviate from the expected for any given laying date. Offspring that had been incubated by young parents had considerably poorer survival than those incubated by mature pairs, despite being reared under standardized, favourable conditions (singly, by mature parents). This was due to increased mortality among female chicks that had been incubated by young parents. The chicks incubated as eggs by young and mature birds, which survived until fledging, did not differ in body mass and size growth, or body condition. The results of this study demonstrate that parental age can influence offspring performance via variation in incubation environment, and that females are more susceptible than males to conditions experienced during embryonic development.     

Sharing of Potential Nest Sites by Etheostoma olmstedi Males Suggests Mutual Tolerance in an Alloparental Species

When reproductive competitors tolerate or cooperate with one another, they may gain particular benefits, such as collectively guarding resources or attracting mates. Shared resources may be those essential to reproduction, such as a breeding site or nest. Using the tessellated darter, a species where males but not females compete over potential nest sites, we examined site use and sharing under controlled conditions of differing competitor density. Sharing was observed even when competitor density was low and individuals could have each occupied a potential nest site without same-sex sharing. Males were more likely to share a nest site with one other when the difference in size between them was larger rather than smaller. There was no evidence that female sharing was dependent on their relative size. Fish were generally more likely to use and share larger sites, in accordance with the greater relative surface area they offered. We discuss how one or both sharing males may potentially benefit, and how male sharing of potential nest sites could relate to female mating preferences. Tessellated darter males are known to provide alloparental care for eggs but this occurs without any social contact between the alloparent and the genetic father of the young. Thus, the suggestion that they may also share sites and maintain social contact with reproductive competitors highlights the importance of increased focus on the potential complexity of reproductive systems.     

Production biology of the upland bully Philypnodon breviceps Stokell in a small New Zealand lake

The life history, food habits, feeding and locomotory activity rhythms of the upland bully, Philypnodonbreviceps Stokell were investigated (February 1969-March 1970) as a basis for studying the relationships between food consumption, biomass and production of the species in a small, moderately eutrophic lake (one of a pair of adjacent lakes at an altitude of 610m in the South Island, New Zealand, known collectively as Spectacles Lakes). Annuli formed on the scales during August and September and could be used as valid indicators of age, although small fish could be aged simply by length frequency analysis. The maximum life-span for both sexes was observed to be 4.5 years but growth of males considerably exceeded that of females. Because females matured at a smaller size than males, mature females were in excess of mature males (3.7: 1). Each female laid only one batch of eggs during a short breeding season in spring (October-December) but several females contributed eggs to each nest. Fecundity ranged from 60–440 eggs per female; the relationship between egg number ( F ) and length ( l ) was log F =–1.609+2.314 log l and between egg number and age ( A )was F =–93.51+109.93 A. Larvae hatched in approximately one month (water temperature 14.4-17.5°C) and the yolk sac became absorbed after a further eight days. Some fry remained pelagic for up to six months. Fry fed predominantly on Crustacea, but the diet changed to larger insect larvae and young of its own species with increasing age and size of the fish. The diet also varied, but to a lesser extent, with season and the time of day. All age groups showed diel rhythms of feeding and locomotory activity which, however, exhibited complex seasonal phase shifts throughout the year. In general, periods of higher feeding intensity appeared to follow closely the periods of increased locomotory activity. The activity level of larger fish was higher than that of smaller fish.     

The effect of parental quality and malaria infection on nestling performance in the Collared Flycatcher (Ficedula albicollis)

Plumage ornamentation often signals the quality of males and, therefore, female birds may choose elaborately ornamented mates to increase their fitness. Such mate choice may confer both direct and indirect benefits to the offspring. Males with elaborate ornaments may provide good genes, which can result in better nestling growth, survival or resistance against parasitic infections. However, these males may also provision their offspring with more food or food of better quality, resulting in nestlings growing at a higher rate or fledging in better condition. In this study, we examined if there was an association between male ornamentation and malaria infection in Collared Flycatchers (Ficedula albicollis). We also investigated offspring performance in relation to malaria infection in the parents and the quality of the genetic and rearing fathers (assessed by the size of two secondary sexual characters) under simulated good and bad conditions (using brood size manipulation). We found that secondary sexual characters did not signal the ability of males to avoid parasitic infections, and malaria infection in the genetic and the rearing parents had no effect on nestling growth and fledging size. Our results do show, however, that it may be beneficial for the females to mate with males with a large forehead patch because wing feathers of nestlings reared by large-patched males grew at a higher rate. Fast feather growth can result in earlier fledging which, in turn, could improve nestling survival in highly variable environments or under strong nest predation.     

Parental care behavior in the monogamous,sexually dimorphic Madagascar paradise flycatcher: sex differences and the effect of brood size

I studied the parental care behavior of the Madagascar paradise flycatcher Terpsiphone mutata in northwestern Madagascar. I especially focused on feeding, brooding and vigilance behaviors. Feeding rate did not differ between males and females, but females spent more time at the nest than males. Females dedicated their time to brooding, while males perched on the nest and were vigilant. Both parents changed the feeding rate in relation to brood size, so the feeding rate per nestling was not different among nests of different brood size. Duration of brooding by females increased with decreasing brood size, suggesting that the Royama effect, the pattern of lower feeding rate per nestling in larger broods, did not apply in this study. Males spent more time on vigilance than females. Anti-predator vigilance by males should be important for nestling survival given the high predation pressure typical of this population. In conclusion, males provide considerable parental care probably to minimize nestling starvation and to avoid nest predation. My results are not consistent with the general pattern of less parental effort by males in monogamous, sexually dimorphic species.     

Complex patterns of food allocation in asynchronously hatching broods of crimson rosellas

In birds, asynchronous hatching typically leads to lower growth and survival of last-hatched chicks. However, all crimson rosella Platycercus elegans, chicks grow at the same rate, although first-hatched chicks can be as much as seven times heavier than last-hatched chicks at the end of hatching. We examined the delivery and distribution of food to 18 rosella broods by videotaping feeds and simultaneously recording mass changes in the nestbox using a digital balance. Parents visited the nest infrequently and delivered loads of up to 25% of their body weight during a feeding visit. Male rosellas consistently delivered larger loads and consequently had higher feeding rates (g/h) than females. Parents distributed food between chicks by direct regurgitation in a series of up to 51 food transfers. Overall, chicks of all hatching ranks received equal numbers of transfers, but parents differed in how they distributed food within the brood. Males fed first-hatched chicks more than last-hatched chicks, whereas females distributed food equally to all chicks. Selective feeding of small chicks might be costly to females since they delivered food more slowly than males and spent more time in the nestbox. Thus female rosellas may invest more in current reproduction than males. Parents also distributed food differently to male and female chicks. Large males were fed more than all other nestlings, while female nestlings were fed equally irrespective of size. This study confirms that complex patterns of parental allocation occur in wild populations. Copyright 1999 The Association for the Study of Animal Behaviour.     

Dynamics of House Sparrow Biparental Care: What Contexts Trigger Partial Compensation?

Nest attendance during incubation is characterized by an inequitable division of labor in house sparrows, Passer domesticus, with females spending more time at the nest than males. Previous research has shown that if male contributions are reduced experimentally via testosterone (T) implants, females compensate partially for those reductions, consistent with predictions from most models of negotiated biparental care. In this study, we attempted to identify the cues and contexts generating partial compensation, using data from both unmanipulated parents and pairs with T‐males. Both males and females of this species sometimes leave the nest before their mate returns to relieve them, and we found that these unrelieved departures by unmanipulated individuals occur when partners are on lengthy recesses. Females compensated partially for long male recesses by marginally extending their bouts; most females also slightly reduced their next recess. By contrast, when males left before their mate returned, they left earlier than when they waited for the female. Neither males nor females adjusted their recess lengths after returning to the nest and discovering that their partner was absent. More pronounced changes in nest attendance of unmanipulated parents occurred in the context of ‘visits’, when individuals returned to the nest but then left without relieving their mate. Such visits effectively prolonged the bout of the on‐duty partner and extended the visitor’s recess. Analyses of behavior of T‐males and their mates revealed that T‐males had significantly longer recesses than control males, and that their mates, in turn, had elevated rates of unrelieved departures. T‐males also visited their on‐duty mates more often than control males, whereas female visits to T‐males were rare. Collectively, the predicted changes in female nest attendance associated with lengthy male recesses and male and female visits account reasonably well for the compensatory response of females paired to T‐males. The majority of female compensation was attributable to changes in visit behavior, however, suggesting that much of the negotiation over nest attendance in this species occurs during direct interactions between mates.     

Evolution of reversed sexual size dimorphism and role partitioning among predatory birds, with a size scaling of flight performance

To explain the adaptive significance of sex role partitioning and reversed sexual size dimorphism among raptors, owls and skuas, where females are usually larger than males, we combine several previous hypotheses with some new ideas. Owing to their structural and behavioural adaptations for prey capture, predatory birds have better prospects than other birds of defending their offspring against nest predators. This makes sex role partitioning advantageous; one parent guards the offspring while the other forages for the family. Further, among predators hunting alert prey such as vertebrates, two mates because of interference may not procur much more food than would one mate hunting alone. By contrast, two mates feeding on less alert prey may together obtain almost twice as much food as one mate hunting alone. For these reasons, partitioning of breeding labours might be adaptive only in predatory birds. An initial imbalance favours female nest guarding and male foraging: the developing eggs might be damaged if the female attacks prey; their mass might reduce her flight performance; she must visit the nest to lay; and the male feeds her before she lays (‘courtship feeding’). Increased female body size should enhance egg production, incubation, ability to tear apart prey for the young, and, in particular, offspring protection in predatory birds. Efficient foraging during the breeding period then becomes most important for the male. This imposes great demands on aerial agility in males, particularly among predators of agile prey. Flight performance decreases with increasing size in five of six aspects explored. The male must therefore not be too large in relation to the most important prey. For these reasons, he should be smaller than the female. Among predatory birds, size dimorphism increases with the proportion of birds in the diet, which may be explained as follows. Adult birds have mainly one type of predators: other predatory birds. Because almost only these specialists exploit adult birds, they carry out most of the cropping of this prey. A predator of easier prey competes with many other kinds of predators, which considerably reduce prey abundance in its territory. This is not so for predators of adult birds. Further, because birds are extremely agile, the specialized predator can hunt efficiently only within a limited size range of birds, whose flight skill it can match. Increased size dimorphism among these predators therefore should be particularly important for enlarging the combined food base of the pair. A bird specialist may consume much of the available prey in the suitable size range during the breeding period. When the predator's young are large enough to defend themselves, the female aids better by hunting than by guarding the chicks. It is advantageous among bird specialists if she hunts prey of other sizes than does the male, who has by then reduced prey abundance in his prey size class. But among predatory birds hunting easier prey the female gains little by hunting outside the male's prey spectrum, because other kinds of predators will have reduced the prey abundance outside as well as inside the male's preferred size range. Intra-pair food separation through large sexual size dimorphism therefore should be particularly advantageous among predators of birds. This may be the main reason why the degree of size dimorphism increases with the dietary proportion of birds.     

Mate Choice and Spawning Success in the Fighting Fish Betta splendens: the Importance of Body Size, Display Behavior and Nest Size

Courtship displays should be exaggerated enough to attract mates and yet tempered so as not to deter them. We tested this hypothesis in the fighting fish Betta splendens by studying courtship displays and body size and their relationships with male parental quality and female fecundity, as well as the effects of display behavior and body size on mate choice decisions and spawning success. Because of their high degree of parental investment, males are expected to be discriminating in their choice of mates. Males who displayed more frequently built larger nests, a measure of parental quality, but larger males did not. When females were paired with males with high display rates, however, the pair had fewer eggs in their nest, even when accounting for female body mass. In a mate choice test using computer‐generated male stimuli that differed only in display behavior, females showed no preferences for displaying males vs. non‐displaying males, or for males with higher display rates vs. lower display rates. In similar tests in which the computer‐generated males differed only in size, females preferred larger males, but also preferred males that differed with respect to body size (negative assortative mating). Males preferred computer‐generated females that performed courtship displays over non‐displaying females, but showed no preferences for female body size. Neither a female's body size nor her display behavior was a significant predictor of her fecundity as estimated by the number of eggs released during spawning. Thus, our results suggest that female B. splendens must balance male parental quality (nest size) with the risk of potentially disruptive or dangerous behavior during spawning, and that females may minimize these risks through negative size‐assortative mating. Female display behavior, while unrelated to fecundity in our study, may attract males because it indicates reproductive readiness or serves a species‐recognition function.     

Males Exhibit Novel Relationships of Dominance with Nest Departure in the Social Paper Wasp Mischocyttarus mastigophorus (Hymenoptera: Vespidae)

In many animal societies, an individual's opportunities to reproduce correspond to their position in a dominance hierarchy. In primitively eusocial paper wasps, female social dominance and direct reproduction are positively associated with taking food from nest mates, but both negatively correlate with foraging flights. Female paper wasps reproduce by laying eggs in their nest, while males reproduce by leaving the nest to copulate. Males of Mischocyttarus mastigophorus are unusual because they reside on their natal nests for prolonged periods, and males direct aggression towards female nestmates. Mischocyttarus mastigophorus males provide an opportunity to further analyse the relationships between dominance, nutrition and nest departure. We found males' rates of social aggression, food taking behaviour, and rates of nest departure were positively correlated. Furthermore, males that initiated aggression at younger ages also began flying earlier, and males engaged in all three behaviours at younger ages than females. Male social aggression may lead to nutrient acquisition, which enable males to depart from the nest. We hypothesise that male nest departure could be adaptive if it increases male mating opportunities. This could account for the positive relationship between dominance and nest departure for males.     

Breeding behaviour of the Bearded Vulture Gypaetus barbatus: minimal sexual differences in parental activities

Monogamous biparental care is expected to occur when opportunities for extra-pair copulations are rare, and both parents are required to raise the chick. Bearded Vultures Gypaetus barbatus fulfill these conditions. Contributions by male and female Bearded Vulture to nest building, nest defence, incubation, nest attendance and chick feeding were studied over five years in eight pairs from the Pyrenees [Catalonia, northeast Spain). Overall, the sexes show equal investment, although the degree of parental effort developed differs depending on the specific activities. During pre-laying, males were significantly more active than females in supplying material to the nest and in territorial defence behaviour, which increased (in both sexes) as the season advanced. Incubation was shared equally both by day and by night. During chick-rearing, the nest was attended by both sexes and the presence of both parents at the nest decreased in parallel with the growth of the chick. Activities related to chick feeding were also equally divided. These results are discussed in the context of female selection of mates and the particular ecology of this species.     

The determinants of sexual segregation in the scalloped hammerhead shark,Sphyrna lewini

Synopsis Female scalloped hammerhead sharks move offshore at a smaller size than do males to form schools composed primarily of intermediate size female sharks. This movement results in smaller females feeding more on pelagic prey than do males and with greater predatory success. It is contended that this change in habitat causes females to grow more rapidly to reproductive size. Intermediate size females grow at a more rapid rate than males. Female scalloped hammerhead sharks mature at a size larger than males. For many elasmobranch species, females: (1) occupy a different habitat, (2) grow more rapidly prior to maturity and continue growth following maturation, (3) feed on different prey with increased feeding success, and (4) reproduce at a size larger than males. It is suggested that female segregation increases fitness, resulting in more rapid growth for the former sex. The females reach maturity at the larger size necessary to support embryonic young, yet similar age to males, matching the female reproductive lifetime to that of males.     

Variation in life-history traits of male Japanese fluvial sculpin Cottus pollux in relation to nest abundance along a stream course

Life-history theory predicts the occurrence of variation in the life-history traits of fish populations under different environmental conditions; however, most studies have focused on such variation between geographically separated populations. We compared breeding characteristics and life-history traits of the Japanese fluvial sculpin (Cottus pollux), a bottom-dwelling nest-holding fish, between two adjacent sites sub-divided by a weir along a stream course in central Japan. Males in the area with a lower abundance of nest sites reached sexual maturity at an earlier age and had a shorter life span than males in the area with sufficient nest abundance. Size-dependent male reproduction was found only in areas with a shortage of nest sites, supporting the assumption of competitive exclusion among males for nests. Females matured at the same age in both sites with no differences in age-specific growth rates and mortality. Our results provide evidence for life-history variation in age and size at maturity and age-specific mortality schedule of males in nest-holding fishes in a single stream population via different sexual selection regimes related to differences in nest abundance between sites.     

Incubation feeding by male Scarlet Tanagers: a mate removal experiment

ABSTRACT Incubation feeding, where males feed their mates, is a common behavior in birds and may improve female condition, nest attentiveness, and nesting success. We used behavioral observations and a temporary mate removal experiment to test the female nutrition hypothesis for incubation feeding by male Scarlet Tanagers (Piranga olivacea). All males (N= 20) were observed incubation feeding and fed females both at the nest (x? 1.36 trips/h) and away from the nest (x? 20.1 trips/h). Male feeding rate off‐nest was negatively correlated with the duration of female foraging bouts and positively correlated with the total time females spent incubating per hour. Eggs were predated at seven of 19 (37%) nests, but nest survival during incubation was not related to either female incubation behavior or male feeding rate. During temporary removal experiments (N= 12), female Scarlet Tanagers remained on the nest significantly longer and did not have longer foraging bouts. An unexpected outcome of the removal experiments was a dramatic change in female vocal behavior. All 12 experimental females gave chik‐burr calls during the male‐removal experiments (x? bout length = 11.7 min), but during normal observation periods only six of 20 females at the incubation stage gave chik‐burr calls (x? bout length = 0.7 min, N= 20). Our results suggest that female tanagers likely gain nutritional benefits from incubation feeding, but male feeding may not improve immediate reproductive success. Nine of 54 (17%) nestlings in five of 17 broods (29%) were extra‐pair young (EPY), indicating that males could potentially benefit from incubation feeding via mate retention and fidelity as well as, or instead of, through immediate gains in reproductive success. Our study indicates that females benefit from incubation feeding and do not simply passively accept food from their mates, but instead may influence male feeding rates through direct (e.g., mate following and vocalizing) and indirect (the threat of mate abandonment or cuckoldry) means.     

Mate choice by marsh wrens: the influence of male and territory quality

If females choose breeding situations to maximize their fitness, then those features of the male and/or territory that are important in mate selection by females should affect female fitness, be assessable prior to mating, and vary among males. The purpose of this study was to identify characteristics of male quality and territory quality that fit these criteria for marsh wrens Cistothorus palustris. The male's contribution to nest defence appeared not to affect female success or choice. However, females that received male assistance with feeding young produced more and heavier fledglings than females without assistance. Males that fed young did not attract more mates. Few males in this population fed young, and no relationship was found between feeding effort and physical or behavioural features of the male. Results of multivariate analyses suggest that, within sites, the measures of territory quality used here cannot explain the variance in the number of young fledged per female or male harem size. The examination of arbitrary territories showed that male pairing success, female settlement order and predation patterns were not significantly correlated between years. The results suggest that territory quality does not influence female success or choice. These results are discussed in the light of earlier attempts to relate features of males and territories to mate selection by female passerines.     

Nest Building and Mating in Relation to Male Size in Corkwing Wrasse, Symphodus Melops

This study examines nest building and mating in relation to size in male corkwing wrasse, Symphodus melops, in the absence of male–male competition. We kept males of varying size together with mature females in tanks containing adequate materials and sites for nest construction. Our results indicate that the size of territorial males does not influence the ability to construct a nest. However, larger males initiated nest building earlier than smaller males and nest size correlated positively with male size. Furthermore, male size did not affect whether or not a nesting male succeeded in mating, indicating that male size was not essential for female acceptance (i.e. whether or not a female is willing to mate) of a male in the current situation.     

Food consumption and growth of larvae and juveniles of three cyprinid species at different food levels

Synopsis The relationships between food availability, consumption and growth were analyzed from the onset of feeding to an age of 90 days in three cyprinid species. Fish were held at 20 ± 0.5° C and given two (three) constant rations of approximately 30, (40) or 100% dry body weight (dbw) ind^-1 day^-1. Food consisted of living zooplankton, the size of which correlated with fish size. At high food densities consumption rates decreased rapidly with fish size in all three species. At reduced rations, fish consumed most of the food offered until they were larger than 10 mg dbw. In all species and at each feeding level daily rations consumed increased allometrically with body size. Respiration rate, expressed as routine metabolic rate differed insignificantly between the three species. At high ration levels, growth rates of small bleak, Alburnus alburnus, were distinctly lower than those of roach, Rutilus rutilus, and blue bream, Abramis ballerus. At low food supply all three species grew at similar rates. Assimilation efficiency at low food conditions was approximately twice that of the well-fed groups. If the caloric equivalents of oxygen consumption as measured in well-fed fish are applied to fish fed at low rations their energy budgets do not balance. This indicates the limitations of fish larvae in the partitioning of energy for growth or activity at such conditions.