The Conflict between Nest Guarding and Mate Guarding in Penduline Tits (Remiz pendulinus)

In penduline tits (Remiz pendulinus), polygynous males build several very elaborate nests successively during one breeding season to attract females. The time and effort invested in nest building is positively related to their mating success. Intraspecific competition for nest material resulting in nest material theft, delays males' nest building progress which in turn decreases their mating success. Therefore, a nest guarding strategy was predicted. In many bird species, males develop some kind of paternity strategy during the female fertile phase. However, as nest building and the female fertile phase frequently coincide, one would expect a trade-off between these strategies. In this study we determined in particular how nest guarding in males conflicts with their mate guarding behaviour in penduline tits. Our results show that nest building is costly in terms of a male's time budget. Thieves benefit by increasing their rate of acquiring nest material which reduces the effort invested in nest building. Nest guarding is an efficient strategy to avoid thieves, as indicated by the negative relation between the presence of the male near the nest and the frequency of nest material theft. Nest guarding is required for the whole building period but males, however, increased their mate guarding effort during the peak fertile phase to ensure their paternity. The data suggest that, for the trade-off “mate guarding versus nest guarding”, paternity insurance seems to be more important.     

Sexual conflict over care: antagonistic effects of clutch desertion on reproductive success of male and female penduline tits

A fundamental tenet of sexual conflict theory is that one sex may increase its reproductive success (RS) even if this harms the other sex. Several studies supported this principle by showing that males benefit from reduced paternal care whereas females suffer from it. By investigating penduline tits Remiz pendulinus in nature, we show that parental conflict may be symmetric between sexes. In this small passerine a single female (or male) cares for the offspring, whereas about 30% of clutches are deserted by both parents. Deserting parents enhance their RS by obtaining multiple mates, and they reduce the RS of their mates due to increased nest failure. Unlike most other species, however, the antagonistic interests are symmetric in penduline tits, because both sexes enhance their own RS by deserting, whilst harming the RS of their mates. We argue that the strong antagonistic interests of sexes explain the high frequency of biparental desertion.     

The effect of ectoparasite nest load on the breeding biology of the Penduline Tit Remiz pendulinus

In this study we investigated the importance of ectoparasite load in the nest on the breed-ing system of the Penduline Tit Remiz pendulinus, examining the effect of mite abundance in the nest on mate choice, reproductive success and parental effort. The two most common ectoparasites were the Northern Fowl Mite Dermanyssus hirundinis and the Northern Feather Mite Ornithonyssus sylviarum. The results show that mite load is important in mate choice but has no adverse effect on reproductive success. The results also indicate that infestation level is related to the quality of the male (mask-width). Parental feeding rate was negatively related to mite load. This relationship indicated that Penduline Tits did not compensate for higher parasite loads by increasing feeding but rather reflected the con dition of the parent and its investment in self-maintenance behaviour.     

Egg burial in penduline tits, Remiz pendulinus: its role in mate desertion and female polyandry

One important component in the mating strategy of an already-matedindividual is the decision to remain with the partner and carefor the offspring or to desert. Almost all research on nestdesertion has focused on the costs and benefits of continuedparental care versus desertion of both parents. However, ifit pays both parents to desert, the timing of desertion is mostimportant. In birds, where all eggs are fertilized well beforethe last egg is laid, males should be the first to desert. Evenif females try to hide their fertile period, it is likely thatthe appearance of eggs acts as a cue that males can use to calculatethe timing of their desertion. Here we examine egg burial behaviorin penduline tits and its possible effects on parental behaviorand desertion. Penduline tits perform uniparental care fromthe earliest point of breeding, and both sexes try to becomepolygamous. We found that 36% of investigated males were polygynousand deserted as soon as the first egg appeared in their nest,and 12.5% of females became polyandrous. About 27% of the nestswere deserted by both sexes, which means high costs for femalesin terms of wasted energy in eggs and for males in terms ofwasted energy and time in building elaborate nests. Femalescover the eggs, and several facts indicate that egg coveringis a deceptive behavior of females: (1) females cover the eggsin the morning before leaving the nest for the first time, (2)females are more aggressive toward their mates during the layingperiod than before laying, (3) females try to prevent malesfrom entering the nest when eggs have been experimentally uncovered,and (4) females uncover the eggs as soon as males are experimentallyremoved. Finally, we found that a female can only desert thenest before the male deserts when she covers the eggs. We concludethat the higher the proportion of eggs a female can hide, thegreater her chance of becoming polyandrous     

Sexual conflict over parental investment in repeated bouts: negotiation reduces overall care

Understanding the evolution of parental care is complicated by the occurrence of evolutionary conflicts of interest within the family, variation in the quality and state of family members, and repeated bouts of investment in a family of offspring. As a result, family members are expected to negotiate over care. We present a model for the resolution of sexual conflict in which parents negotiate over repeated bouts of care. Negotiation is mediated by parents deciding at the start of each bout how much care to give on the basis of the state (mass) of offspring, which reflects the amount of care previously received. The evolutionarily stable pattern of care depends on whether the parents care together for the whole family, or each cares alone for part of the divided family. When they care together, they provide less care in the first bout, more in the last bout, and less care overall, resulting in lower parental and offspring fitness. Our results emphasize that negotiation over parental care may occur as a means of avoiding exploitation owing to sexual conflict, even in the absence of variation in the quality of either sex of parent, and lead to a reduction in fitness.     

Sexual conflict about parental care: the role of reserves

Parental care often increases the survival of offspring, but it is costly to parents. Because of this trade-off, a sexual conflict over care arises. The solution to this conflict depends on the interactions between the male and female parents, the behavior of other animals in the population, and the individual differences within a sex. We take an integrated approach and develop a state-dependent dynamic game model of parental care. The model investigates a single breeding season in which the animals can breed several times. Each parent's decision about whether to care for the brood or desert depends on its own energy reserves, its mate's reserves, and the time in the season. We develop a fully consistent solution in which the behavior of an animal is the best given the behavior of its mate and of all other animals in the population. The model predicts that females may strategically reduce their own reserves so as to "force" their mate to provide care. We investigate how the energy costs of caring and searching for a mate, values of care (how the probability of offspring survival depends on the pattern of care), and population sex ratio influence the pattern of care over the breeding season.     

Sexual conflict over parental care promotes the evolution of sex differences in care and the ability to care

Strong asymmetries in parental care, with one sex providing more care than the other, are widespread across the animal kingdom. At present, two factors are thought to ultimately cause sex differences in care: certainty of parentage and sexual selection. By contrast, we here show that the coevolution of care and the ability to care can result in strong asymmetries in both the ability to care and the level of care, even in the absence of these factors. While the coevolution of care and the ability to care does not predict which sex evolves to care more than the other, once other factors give rise to even the slightest differences in the cost and benefits of care between the sexes (e.g. differences in certainty in parentage), a clear directionality emerges; the sex with the lower cost or higher benefit of care evolves both to be more able to care and to provide much higher levels of care than the other sex. Our findings suggest that the coevolution of levels of care and the ability to care may be a key factor underlying the evolution of sex differences in care.     

Female burying beetles benefit from male desertion: sexual conflict and counter-adaptation over parental investment

Sexual conflict drives the coevolution of sexually antagonistic traits, such that an adaptation in one sex selects an opposing coevolutionary response from the other. Although many adaptations and counteradaptations have been identified in sexual conflict over mating interactions, few are known for sexual conflict over parental investment. Here we investigate a possible coevolutionary sequence triggered by mate desertion in the burying beetle Nicrophorus vespilloides, where males commonly leave before their offspring reach independence. Rather than suffer fitness costs as a consequence, our data suggest that females rely on the male's absence to recoup some of the costs of larval care, presumably because they are then free to feed themselves on the carcass employed for breeding. Consequently, forcing males to stay until the larvae disperse reduces components of female fitness to a greater extent than caring for young singlehandedly. Therefore we suggest that females may have co-evolved to anticipate desertion by their partners so that they now benefit from the male's absence.     

Brood desertion in Kentish plover: the value of parental care

To understand the evolution of parental care, one needs to estimatethe payoffs from providing care for the offspring and from terminatingcare and deserting them. In this study we estimated the payofffrom care provision, and in a companion paper we analyze thepayoff from offspring desertion. In the current study we experimentallyinvestigated the influence of the number and sex of attendingparents on growth and survival of offspring in the Kentish ploverCharadrius alexandrinus, in two sites (A and B). Either the maleor the female parent was removed from some broods at hatchingof the chicks (female-only and male-only broods, respectively),whereas in control broods both parents were allowed to attendtheir young. At site A survival of the chicks was lower in uniparental(male-only and female-only) broods than in control broods, whereaswe found no difference in brood survival at site B. Brood survivaldecreased over the season. Removal of either parent did not influencethe growth of the young, although growth varied over the breeding season,and it was significantly different between the sites. Theseresults suggest that the payoff from parental care decreasesover the breeding season and that the value of parental care(i.e., the contribution of parents to the survival of theiryoung) may depend on the environment.     

Polymorphic microsatellite DNA markers in the penduline tit, Remiz pendulinus

To describe the exceptional mating system of the penduline tit, Remiz pendulinus, we aim to combine field observation records with DNA analysis based on polymorphic microsatellite DNA markers. Here we describe features of nine loci and their corresponding polymerase chain reaction primers. The observed number of alleles varied from four to seven and the observed heterozygosity ranged from 0.419 to 0.802. Neither of the loci is sex-linked and as linkage disequilibrium analysis showed they assort independently. Seven of the nine loci were polymorphic in the Cape penduline tit, Anthoscopus minutus.     

广西发现中华攀雀

<正>2012年11月28日、12月8日和2013年1月16日,在广西南宁市大王滩水库(22°35′N,108°19′E)周边的芦苇、灌丛及树林等生境中观察到9~28只成群的雀形目鸟类,并采集到5号标本(2♂,3♀)。该鸟雌雄相似,但雄性额基、颊和耳羽可见淡淡的黑色,且下体颜色相对较深,经鉴定为中华攀雀(Remiz consobrinus)。标本量衡度参见表1。     

Sexual conflict and parental care in magnificent frigatebirds: full compensation by deserted females

Parental care is a cooperative venture between a male and a female in many socially monogamous birds. Care is costly, and thus, sexual conflict arises between the parents about how much effort they should invest into rearing their young. The sexual conflict over care is most apparent when one parent abandons the brood before the offspring are independent. The deserted parent has three options: (1) desert the brood because a single parent is unable to raise the young on its own; (2) continue care provision at the same level as during biparental care, and thus do not compensate for the absence of mate; or (3) increase care and compensate partially or totally. We investigated these options in the magnificent frigatebird, Fregata magnificens, a species in which the male deserts his mate and brood before the chick is independent. During biparental care, females fed the chick more often than the males. After their mate deserted, the females nearly doubled their feeding rate and thus, fully compensated for the lost care. Consistent with these observations, growth rates of chicks provided with biparental and female-only care did not differ. These results support recent theoretical models of parental care, and suggest that females may withhold care during biparental care to manoeuvre their mates into prolonged care provision. A female only provides at her full capacity once her mate has deserted.     

Sexual conflict and consistency of offspring desertion in Eurasian penduline tit <Emphasis Type="Italic">Remiz pendulinus</Emphasis>

Background  

The trade-off between current and future parental investment is often different between males and females. This difference may lead to sexual conflict between parents over care provisioning in animals that breed with multiple mates. One of the most obvious manifestations of sexual conflict over care is offspring desertion whereby one parent deserts the young to increase its reproductive success at the expense of its mate. Offspring desertion is a wide-spread behavior, and its frequency often varies within populations. We studied the consistency of offspring desertion in a small passerine bird, the Eurasian penduline tit Remiz pendulinus, that has an extremely variable breeding system. Both males and females are sequentially polygamous, and a single parent (either the male or the female) incubates the eggs and rears the young. About 28–40% of offspring are abandoned by both parents, and these offspring perish. Here we investigate whether the variation in offspring desertion in a population emerges either by each individual behaving consistently between different broods, or it is driven by the environment.     

Offspring desertion and parental care in the Whiskered Tern Chlidonias hybrida

In species with biparental care, a conflict of interest can arise if one mate tries to maximize its own reproductive success at the expense of the other's. One of the mates can desert the brood to accrue a number of benefits to enhance its own fitness, leaving parental care to the remaining parent. This study is the first to describe the desertion pattern in a tern species (Sternidae). We investigated offspring desertion in the Whiskered Tern Chlidonias hybrida, a species with semi‐precocial chicks. Offspring desertion was recorded in 52% of nests prior to fledging (n = 131 nests). Females also deserted during the post‐fledging period. Of the deserters, 97% were females. Desertions started when chicks were 5 days old and no longer required intense brooding. Desertions before fledging did not affect fledging success. Provisioning rates between pair members differed, and females supplied much less food than males. Female provisioning rate affected the chances of nest desertion significantly: daily desertion rates were lower when females supplied more food. After females had deserted, males increased their provisioning rates but compensated for the loss of female care only partly in two‐ and three‐chick broods. Only in small (one‐chick) broods was compensation full. We conclude that male and female Whiskered Terns adopt different reproductive strategies in the population studied here. Females invest much less in parental care than males, providing less food and deserting more frequently. Given the ready availability of food and low predation pressure, benefits appear to accrue to females that desert; selection forces may therefore not be acting against female desertion.     

新疆北部白冠攀雀的巢与巢址选择

2008年4—7月,在新疆北部对白冠攀雀巢址选择进行了研究。白冠攀雀的营巢习性特殊,巢呈囊袋状,结构甚为精致。对于白冠攀雀巢的研究,采用总面积调查法,进行地毯式的搜寻,并结合标图法对其进行标记,绘制分布图。研究结果共发现巢125个,营巢位于于临近湖泊、河流等水域附近的柳树、杨树、桦树等阔叶树上。营巢树种以柳树为主,占68.80%。巢的高度平均为(5.3±2.5)m,营巢于乔木的中下部（约1/3处）,约70%的巢离河边不足30 m。对于巢址选择的研究,将原始记录中与巢址选择有关的特征变量进行主成分分析,分析表明,影响白冠攀雀巢址选择的主要因素有4种,依次为：郁闭度因素（包括营巢树胸径、巢上郁闭度）、营巢树种因素(包括营巢树种、树高、巢位高度和乔木种类)、方位因素（包括距河边距离和巢向）、食物与巢材因素。     

Individual variation and the resolution of conflict over parental care in penduline tits

Eurasian penduline tits (Remiz pendulinus) have an unusually diverse breeding system consisting of frequent male and female polygamy, and uniparental care by the male or the female. Intriguingly, 30 to 40 per cent of all nests are deserted by both parents. To understand the evolution of this diverse breeding system and frequent clutch desertion, we use 6 years of field data to derive fitness expectations for males and females depending on whether or not they care for their offspring. The resulting payoff matrix corresponds to an asymmetric Snowdrift Game with two alternative evolutionarily stable strategies (ESSs): female-only and male-only care. This, however, does not explain the polymorphism in care strategies and frequent biparental desertion, because theory predicts that one of the two ESSs should have spread to fixation. Using a bootstrapping approach, we demonstrate that taking account of individual variation in payoffs explains the patterns of care better than a model based on the average population payoff matrix. In particular, a model incorporating differences in male attractiveness closely predicts the observed frequencies of male and female desertion. Our work highlights the need for a new generation of individual-based evolutionary game-theoretic models.     

Old nests are cues for suitable breeding sites in the Eurasian penduline tit Remiz pendulinus

Nest-sites often have a major influence on avian reproductive success. The use of reliable cues that assist nest-site selection should thus be favoured by natural selection. The old nests have been known to serve as a cue in nest-site selection in several species. To find out whether the old nests act as cue in nest-site selection in the Eurasian penduline tit Remiz pendulinus , we carried out two experiments in southern Hungary, where the penduline tits breed around fishponds and build sophisticated pendulous nests on tree branches that often hang over water. In April 2006, we choose 20 groups of two nearby trees, and hung an old nest on one of the trees in each group. The male penduline tits choose 12 of these groups to build a new nest, and every of the twelve nests were built on trees with an old nest. This suggests that the old nests serve as a cue in the selection of breeding sites for males when they enter a habitat. To find out whether the old nests are cues of plentiful nest building material, or to signal high quality breeding areas, we carried out a second experiment in 2007 by selecting 13 groups of three nearby trees. A "worn-out" old nest was hung on one of the trees, a "re-utilize" type of old nest on another tree, whereas the third tree was left without an old nest in each group. The rationale was that while the worn-out material of the old nests is of no use in building the new nests, material of the "re-utilize" nests is good enough to be used for building new nests. Males built a new nest in 10 of the 13 groups, and eight of the new nests were built on trees with an old nest. Of the eight new nests, five were built on trees with a "worn-out" old nest and three on trees with a "re-utilize" type of old nest. It appears that for the penduline tit males it is the presence of an existing old nest and not the quality of the old nest material that serves as cue during the selection of the suitable breeding sites.