人工巢箱条件下两种山雀鸟类的同域共存机制

种间竞争会导致鸟类对自身的生存策略进行多方面调整,将多种因素结合起来分析不同鸟类的同域共存机制具有十分重要的意义.2009-2011年的3-7月,在辽宁省东部山区以悬挂人工巢箱的方法招引杂色山雀(Parus varius)和大山雀(Parus major),通过比较这两种鸟类在繁殖时间、繁殖参数和巢址选择上的差异,分析其繁殖期的栖息地选择及繁殖对策,探讨这两种鸟类同域共存的机制.结果表明,生态位的部分分离是大山雀和杂色山雀能够长期共存的基础.两者都是在繁殖期到来立即开始繁殖,均出现两次繁殖高峰,采用消减窝卵数的对策来适应环境质量的下降.对繁殖参数的分析表明,两种鸟类的繁殖对策都为k-选择,但大山雀略偏向r端,大山雀倾向高窝卵数、低繁殖成功率的繁殖策略;杂色山雀倾向低窝卵数、高繁殖成功率的繁殖策略.两种鸟类都选择在林龄较长的森林中筑巢,但是大山雀较注重巢址的安全性能,巢距地面较高,周围乔木密集;杂色山雀较为注重植被类型的选择,巢址多选择在植被多样、灌木生长茂盛的针阔混交林中,推测可能与杂色山雀的食物构成有关.     

Lazy group members are substitute helpers in carrion crows

In many cooperatively breeding societies, helping effort varies greatly among group members, raising the question of why dominant individuals tolerate lazy subordinates. In groups of carrion crows Corvus corone corone, helpers at the nest increase breeders'' reproductive success, but chick provisioning is unevenly distributed among non-breeders, with a gradient that ranges from individuals that work as much as the breeders to others that completely refrain from visiting the nest. Here we show that lazy non-breeders represent an insurance workforce that fully compensates for a reduction in the provisioning effort of another group member, avoiding a decrease in reproductive success. When we temporarily impaired a carer, decreasing its nest attendance, the laziest non-breeders increased their provisioning rate and individuals that initially refrained from visiting the nest started helping. Breeders, in contrast, did not increase chick provisioning. This shows that lazy non-breeders can buffer a sudden unfavourable circumstance and suggests that group stability relies on the potential contribution of group members in addition to their current effort.     

Costly reproductive competition between females in a monogamous cooperatively breeding bird

In many cooperatively breeding societies, only a few socially dominant individuals in a group breed, reproductive skew is high, and reproductive conflict is common. Surprisingly, the effects of this conflict on dominant reproductive success in vertebrate societies have rarely been investigated, especially in high-skew societies. We examine how subordinate female competition for breeding opportunities affects the reproductive success of dominant females in a monogamous cooperatively breeding bird, the Southern pied babbler (Turdoides bicolor). In this species, successful subordinate reproduction is very rare, despite the fact that groups commonly contain sexually mature female subordinates that could mate with unrelated group males. However, we show that subordinate females compete with dominant females to breed, and do so far more often than expected, based on the infrequency of their success. Attempts by subordinates to obtain a share of breeding impose significant costs on dominant females: chicks fledge from fewer nests, more nests are abandoned before incubation begins, and more eggs are lost. Dominant females appear to attempt to reduce these costs by aggressively suppressing potentially competitive subordinate females. This empirical evidence provides rare insight into the nature of the conflicts between females and the resultant costs to reproductive success in cooperatively breeding societies.     

Nonideal nest box selection by tree swallows breeding in farmlands: Evidence for an ecological trap?

Animals are expected to select a breeding habitat using cues that should reflect, directly or not, the fitness outcome of the different habitat options. However, human‐induced environmental changes can alter the relationships between habitat characteristics and their fitness consequences, leading to maladaptive habitat choices. The most severe case of such nonideal habitat selection is the ecological trap, which occurs when individuals prefer to settle in poor‐quality habitats while better ones are available. Here, we studied the adaptiveness of nest box selection in a tree swallow (Tachycineta bicolor) population breeding over a 10‐year period in a network of 400 nest boxes distributed along a gradient of agricultural intensification in southern Québec, Canada. We first examined the effects of multiple environmental and social habitat characteristics on nest box preference to identify potential settlement cues. We then assessed the links between those cues and habitat quality as defined by the reproductive performance of individuals that settled early or late in nest boxes. We found that tree swallows preferred nesting in open habitats with high cover of perennial forage crops, high spring insect biomass, and high density of house sparrows (Passer domesticus), their main competitors for nest sites. They also preferred nesting where the density of breeders and their mean number of fledglings during the previous year were high. However, we detected mismatches between preference and habitat quality for several environmental variables. The density of competitors and conspecific social information showed severe mismatches, as their relationships to preference and breeding success went in opposite direction under certain circumstances. Spring food availability and agricultural landscape context, while related to preferences, were not related to breeding success. Overall, our study emphasizes the complexity of habitat selection behavior and provides evidence that multiple mechanisms may potentially lead to an ecological trap in farmlands.     

Burrow and mate fidelity in the Little Penguin Eudyptula minor at Lion Island, New South Wales, Australia

Although both mate and nest fidelity are thought to exist in Little Penguins Eudyptula minor , few studies have statistically assessed the relationship between both types of fidelity and breeding success. Observations of the breeding biology of the Little Penguin were carried out between 1990 and 1998 at Lion Island, New South Wales, Australia. The existence of fidelity and the effect of breeding success on subsequent fidelity were assessed for this population. Strong evidence for the existence of nest and mate fidelity was found with high rates of return to the same burrow and mate being recorded for both sexes. For all years of the study, the average number of female and male birds faithful to their nest was 76 and 79%, respectively, with only two noted cases of intraseasonal burrow swapping. The rate of divorce varied widely between years, with a range of 0–40%. A marginal association of a log linear model showed a highly significant relationship ( P  < 0.001) between success of a clutch in one year and fidelity to a mate in the following year. Consequently, parents successfully raising a fledgling in one year were more likely to reunite in the following year than were pairs that attempted unsuccessfully to breed. Pairs failing to fledge chicks were much more likely to separate owing to the absence of one parent in the following year. We were unable to detect any association between breeding success in one year and subsequent change of nest in the next.     

Intermittent breeding in Cory's Shearwater Calonectris diomedea of Selvagem Grande, North Atlantic

Every year, 10% of the breeding population of Cory's Shearwater Calonectris diomedea of Selvagem Grande, between the Canaries and Madeira (30̀09'N, 15̀52'W), fail to breed. These "sabbatical" periods can last up to 7 years but typically last 1 year in 58% of the cases, with an average of 1.7 years. Both sexes are involved, and most are young breeding birds. The frequency and duration of the absences decrease with the increase of breeding experience. During the year preceding the absence, the breeding success, mate fidelity and nest site fidelity of the breeding birds are the same as those of their sabbatical congeners. During the sabbatical absence, the former mate is also absent in just less than half of the cases. Of those present, two-thirds are at the same nest site and one-third at another nest site. On the return of the "missing" birds, the fidelity both to the former mate and the former nest site is low, and more so if the length of the absence has been over 1 year, because the former mate and the former nest site are then seldom available. Divorce is frequent and the breeding success is low. Comparisons with other Procellariiformes reveal few differences in the intermittent breeding except for the proportions involved, which are six times greater for some species than for others.     

Prospecting in the collared flycatcher: gathering public information for future breeding habitat selection?

Visiting breeding patches can allow prospecting individuals to gather information on local patch quality to make optimal decisions about selecting a breeding habitat in the following year. This prospecting behaviour has been described in many bird species. However, the nature of the information gathered by prospectors often remains unknown. We collected data on prospecting behaviour in the collared flycatcher, Ficedula albicollis, a small hole-nesting passerine bird, to investigate whether prospectors could gather information on their conspecifics' reproductive success, that is, ‘public information’. If they could, they would be expected to inspect conspecific nests, prospect at the time when public information is reliable, and be attracted to, and spend time at, successful sites. Prospecting at conspecific nests was frequent. Prospectors were mainly males, and prospecting activity closely matched the peak of nesting activity. The probability of observing a prospector at a nest increased with parental activity, measured by feeding rate and vigilance behaviour, but did not depend on direct measures of success of the inspected nest (nestling number and condition), or on female characteristics. Because feeding rate and vigilance behaviour were predictors of breeding success at fledging, prospectors were attracted to the most successful nests when cueing on conspicuous parental activity. Therefore, prospectors could gather accurate information on local conspecific reproductive success that may be used for breeding patch choice in the following year. We discuss alternative explanations for our results, and the need to test experimentally whether prospectors gather public information. We also discuss the role of breeding constraints on, and the origin of sex differences in, prospecting.     

Cooperation between non-relatives in a primitively eusocial paper wasp,Polistes dominula

In cooperatively breeding vertebrates, the existence of individuals that help to raise the offspring of non-relatives is well established, but unrelated helpers are less well known in the social insects. Eusocial insect groups overwhelmingly consist of close relatives, so populations where unrelated helpers are common are intriguing. Here, we focus on Polistes dominula—the best-studied primitively eusocial wasp, and a species in which nesting with non-relatives is not only present but frequent. We address two major questions: why individuals should choose to nest with non-relatives, and why such individuals participate in the costly rearing of unrelated offspring. Polistes dominula foundresses produce more offspring of their own as subordinates than when they nest independently, providing a potential explanation for co-founding by non-relatives. There is some evidence that unrelated subordinates tailor their behaviour towards direct fitness, while the role of recognition errors in generating unrelated co-foundresses is less clear. Remarkably, the remote but potentially highly rewarding chance of inheriting the dominant position appears to strongly influence behaviour, suggesting that primitively eusocial insects may have much more in common with their social vertebrate counterparts than has commonly been thought.     

Mate fidelity in a polygamous shorebird,the snowy plover (Charadrius nivosus)

Social monogamy has evolved multiple times and is particularly common in birds. However, it is not well understood why some species live in long‐lasting monogamous partnerships while others change mates between breeding attempts. Here, we investigate mate fidelity in a sequential polygamous shorebird, the snowy plover (Charadrius nivosus), a species in which both males and females may have several breeding attempts within a breeding season with the same or different mates. Using 6 years of data from a well‐monitored population in Bahía de Ceuta, Mexico, we investigated predictors and fitness implications of mate fidelity both within and between years. We show that in order to maximize reproductive success within a season, individuals divorce after successful nesting and re‐mate with the same partner after nest failure. Therefore, divorced plovers, counterintuitively, achieve higher reproductive success than individuals that retain their mate. We also show that different mating decisions between sexes predict different breeding dispersal patterns. Taken together, our findings imply that divorce is an adaptive strategy to improve reproductive success in a stochastic environment. Understanding mate fidelity is important for the evolution of monogamy and polygamy, and these mating behaviors have implications for reproductive success and population productivity.     

Mate fidelity in monogamous birds: a re-examination of the Procellariiformes

Mate retention is classically considered advantageous for reproduction in monogamous birds: because of their low fecundity, long-lived species should show the highest year-to-year mate fidelity. However, this hypothesis remains controversial: several studies have found no correlation between mate fidelity and longevity, possibly because they did not control for potential confounding factors on each of these parameters, and one study found a negative correlation in the Procellariiformes (albatrosses and petrels). We re-examined the relations between mate fidelity and longevity, and between mate fidelity and site fidelity, in this group, using our data on 13 species and data from the literature, and after eliminating confounding factors. Procellariiformes are the most long lived of birds despite important interspecific variation in body size, and they show strong mate fidelity and bear high costs of divorce. All species lay only one egg, and the most long lived breed biennially. Because large organisms live longer than small ones and their reproductive effort is lower, we had to control for breeding frequency and body size. Mate fidelity and adult life expectancy were positively correlated, regardless of whether we controlled for these two parameters. We also evaluated whether mate fidelity was related to site fidelity. Biennial albatrosses show high mate fidelity, but low nest fidelity, although they are extremely faithful to a small area around their previous nest. After controlling for body size, adult life expectancy and breeding frequency, we found no correlation between mate fidelity and site fidelity. Because divorce is costly and mate retention advantageous in Procellariiformes, we suggest that mate fidelity does not passively result from site fidelity in these species. Rather, site fidelity would be a means for pairs to reunite, with sites serving as meeting points. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Breeding performance,mate fidelity,and nest site fidelity in a long‐lived seabird: behaving against the current?

There is evidence that breeding failure is associated with divorce and dispersal in many bird species. However, deviations from the general pattern “success‐stay/failure‐leave” seem to be common, suggesting that factors other than breeding performance may importantly influence mate and habitat selection. Moreover, variability in response to performance suggests coexistence of different evolutionary strategies of mate and site selection within a population. In this study, we assessed how individuals conform to the success‐stay/failure‐leave pattern in kittiwakes (Rissa tridactyla), and aimed to identify categories of individuals presenting different behavioural patterns. We considered individual attributes (experience, prior residence at the nest site, performance in multiple breeding attempts), pair attributes (arrival asynchrony, timing of failure, pair duration), and productivity in habitat patches. Timing of failure was an important factor. Pair reunion probability was close to 0.5 in failed pairs, but it was consistently higher in early failed than in late failed pairs. Prior residence better explained variability in probability of reunion in failed pairs than pair duration. However, the positive influence of prior residence on the probability of reunion was perceptible only in early failed pairs. Divorce probability in successful pairs increased with arrival asynchrony, and was higher in first‐time than in experienced breeders. Local productivity positively influenced site fidelity probability in early failed birds, but not in late failed ones. Using memory models, we found that dispersal decisions integrate information on individual breeding performance in a temporal scale longer than one year. This study contributed to the identification of relevant states to be considered when addressing mate and nest site choice. Natural selection may operate on slight fitness differences that cannot be detected without high levels of stratification according to the appropriate individual and habitat attributes.     

Effects of pair migratory behavior on breeding phenology and success in a partially migratory shorebird population

In migratory systems, variation in individual phenology can arise through differences in individual migratory behaviors, and this may be particularly apparent in partial migrant systems, where migrant and resident individuals are present within the same population. Links between breeding phenology and migratory behavior or success are generally investigated at the individual level. However, for breeding phenology in particular, the migratory behaviors of each member of the pair may need to be considered simultaneously, as breeding phenology will likely be constrained by timing of the pair member that arrives last, and carryover effects on breeding success may vary depending on whether pair members share the same migratory behavior or not. We used tracking of marked individuals and monitoring of breeding success from a partially migrant population of Eurasian oystercatchers (Haematopus ostralegus) breeding in Iceland to test whether (a) breeding phenology varied with pair migratory behavior; (b) within‐pair consistency in timing of laying differed among pair migratory behaviors; and (c) reproductive performance varied with pair migratory behavior, timing of laying, and year. We found that annual variation in timing of laying differed among pair migratory behaviors, with resident pairs being more consistent than migrant and mixed pairs, and migrant/mixed pairs breeding earlier than residents in most years but later in one (unusually cold) year. Pairs that laid early were more likely to replace their clutch after nest loss, had higher productivity and higher fledging success, independent of pair migratory behavior. Our study suggests that the links between individual migratory behavior and reproductive success can vary over time and, to a much lesser extent, with mate migratory behavior and can be mediated by differences in laying dates. Understanding these cascading effects of pair phenology on breeding success is likely to be key to predicting the impact of changing environmental conditions on migratory species.     

Delayed timing of breeding as a cost of reproduction

Timing of breeding is a trait with considerable individual variation, often closely linked to fitness because of seasonal declines in reproduction. The drivers of this variation have received much attention, but how reproductive costs may influence the timing of subsequent breeding has been largely unexplored. We examined a population of northern wheatears Oenanthe oenanthe to compare three groups of individuals that differed in their timing of breeding termination and reproductive effort to investigate how these factors may carry over to influence reproductive timing and reproductive output in the following season. Compared to females that bred successfully, females that put in less effort and terminated breeding early due to nest failure tended to arrive and breed earlier in year 2 (mean advancement = 2.2 and 3.3 d respectively). Females that spent potentially more effort and terminated breeding later due to production of a replacement clutch after nest failure, arrived later than other females in year 2. Reproductive output (number of fledglings) in year 2 differed between the three groups as a result of group‐level differences in the timing of breeding in combination with the general seasonal decline in reproductive output. Our study shows that the main cost of reproduction was apparent in the timing of arrival and breeding in this migratory species. Hence, reproductive costs can arise through altered timing of breeding since future reproductive success (including adult survival) is often dependent on the timing of breeding in seasonal systems.     

Cooperative breeding behaviors in the Hawaiian Stilt (Himantopus mexicanus knudseni)

Cooperative breeding, which is commonly characterized by nonbreeding individuals that assist others with reproduction, is common in avian species. However, few accounts have been reported in Charadriiformes, particularly island‐nesting species. We present incidental observations of cooperative breeding behaviors in the Hawaiian Stilt (Himantopus mexicanus knudseni), an endangered subspecies of the Black‐necked Stilt (Himantopus mexicanus), during the 2012–2020 nesting seasons on the Hawaiian islands of O‘ahu and Moloka‘i. We describe two different behaviors that are indicative of cooperative breeding: (a) egg incubation by multiple adults; (b) helpers‐at‐the‐nest, whereby juveniles delay dispersal and reproduction to assist parents and siblings with reproduction. These observations are the first published accounts of cooperative breeding in this subspecies and merit further investigation, as cooperative breeding may improve population viability of the endangered, endemic Hawaiian Stilt.     

Offspring pay sooner,parents pay later: experimental manipulation of body mass reveals trade-offs between immune function,reproduction and survival

Introduction

Life-history theory predicts that organisms trade off survival against reproduction. However, the time scales on which various consequences become evident and the physiology mediating the cost of reproduction remain poorly understood. Yet, explaining not only which mechanisms mediate this trade-off, but also how fast or slow the mechanisms act, is crucial for an improved understanding of life-history evolution. We investigated three time scales on which an experimental increase in body mass could affect this trade-off: within broods, within season and between years. We handicapped adult skylarks (Alauda arvensis) by attaching extra weight during first broods to both adults of a pair. We measured body mass, immune function and return rates in these birds. We also measured nest success, feeding rates, diet composition, nestling size, nestling immune function and recruitment rates.

Results

When nestlings of first broods fledged, parent body condition had not changed, but experimental birds experienced higher nest failure. Depending on the year, immune parameters of nestlings from experimental parents were either higher or lower than of control nestlings. Later, when parents were feeding their second brood, the balance between self-maintenance and nest success had shifted. Control and experimental adults differed in immune function, while mass and immune function of their nestlings did not differ. Although weights were removed after breeding, immune measurements during the second brood had the capacity to predict return rates to the next breeding season. Among birds that returned the next year, body condition and reproductive performance a year after the experiment did not differ between treatment groups.

Conclusions

We conclude that the balance between current reproduction and survival shifts from affecting nestlings to affecting parents as the reproductive season progresses. Furthermore, immune function is apparently one physiological mechanism involved in this trade-off. By unravelling a physiological mechanism underlying the trade-offs between current and future reproduction and by demonstrating the different time scales on which it acts, our study represents an important step in understanding a central theory of life-history evolution.

     

To breed or not to breed: Physiological correlates of reproductive status in a facultatively biennial iguanid

It is unusual for seasonal breeders to frequently skip opportunities for reproduction. We investigated the relationship between physiological state and reproductive decision-making in Galápagos marine iguanas (Amblyrhynchus cristatus), a species in which females typically reproduce biennially, although the proportion of breeding individuals varies significantly across years. Nearly all adult-sized females initiated follicular development prior to the lekking period, but 38% of females resorbed all developing follicles 5-15 days before the start of copulations. Receptive and non-receptive females differed in reproductive hormones during the mate choice period. Testosterone peaked in receptive females immediately prior to copulation, indicating that testosterone or its derivative estradiol likely mediates female receptivity in Galápagos marine iguanas. Non-receptive females showed significant peaks in both testosterone and progesterone during follicular atresia, suggesting that these hormones may be involved in inhibiting vitellogenesis. Two to three weeks prior to the period of reproductive decision-making (and the onset of follicular atresia in non-receptive females) receptive females were in higher body condition, were developing larger follicles, and had lower levels of both baseline and stress-induced corticosterone. Reproduction is extremely costly in this long-lived species, and increases the likelihood of mortality in the year following breeding; females could therefore gain significant benefits from being attuned to indicators of reproductive success. We suggest that corticosterone may modulate reproductive decisions by altering individual sensitivity to both internal and external cues of the likelihood of successful reproduction.     

Effects of site fidelity and breeding performance on mate retention in a short‐lived passerine,the tree swallow Thachycineta bicolor

We studied the relationship among re‐mating, site fidelity and breeding performance in the tree swallow Tachycineta bicolor using 16 y of data on reproductive biology in a population breeding in nest boxes near Ithaca, New York. Of 217 pairs for which both members survived the non‐breeding season, 76% mated with a new partner and 24% reunited with their previous mate. Pairs did not increase their breeding success by breeding together for more than one breeding season. Males produced fewer fledglings after breeding with a new partner, but females neither increased nor decreased their success when breeding with a new mate. Females who bred with a new partner were younger than females that reunited with their previous mates, and they were more likely to move to a different nest box. Males that bred with a new mate were of similar age to males that reunited, and they did not move more often. The probability of breeding with a new partner was better predicted by female age than by previous breeding success, suggesting that re‐mating was not strongly affected by past breeding performance. Because younger females change breeding sites more frequently than do older females and females that mated with a new partner were younger than females that reunited with their previous mates, we suggest that the tendency of tree swallows to change partners between years is a by‐product of lower site fidelity of younger females rather than a strategy for increasing breeding success.     

Optimal level of inbreeding in the common lizard

Mate choice with regard to genetic similarity has been rarely considered as a dynamic process. We examined this possibility in breeding populations of the common lizard (Lacerta vivipara) kept for several years in semi-natural conditions. We investigated whether they displayed a pattern of mate choice according to the genetic similarity and whether it was context-dependent. Mate choice depended on genetic similarity with the partner and also on age and condition. There was no systematic avoidance of inbreeding. Females of intermediate ages, more monogamous, did not mate with genetically similar partners, whereas younger and older females, more polyandrous, did but highest clutch proportions were associated with intermediate values of pair-relatedness. These results indicate dynamic mate choice, suggesting that individuals of different phenotypes select their partners in different ways according to their genetic similarity. We consider our results in the light of diverse and apparently contradictory theories concerning genetic compatibility, and particularly, optimal inbreeding and inclusive fitness.     

Nest positioning by male Daito White‐eyes Zosterops japonicus daitoensis improves with age to reduce nest predation risk

Age‐related improvement in reproductive success is widely observed in birds, and the mechanisms by which productivity is enhanced have received considerable attention. However, little is known about how parental age affects the loss of eggs or nestlings despite the fact that age effects on nesting success are often reported. We examined parental age effects on reproductive success in relation to the avoidance of nest predation in an island subspecies of the Japanese White‐eye, the Daito White‐eye Zosterops japonicus daitoensis. Clutch size and annual number of breeding attempts did not differ between parental age classes. Reproductive success was affected only by male age through an increase in nesting success. Nest failure was attributed only to predation in this species and nest concealment and nest height were important nest characteristics promoting successful fledging. Older males built their nests in more concealed and higher positions than first‐year birds, regardless of vegetation status around the nest. Analysis of individual birds suggested that by shifting the nest to a safer position, male White‐eyes achieved higher nesting success than in the previous year. Of three hypotheses of age‐related improvement in reproductive success considered, our data favoured the hypothesis that as individuals grow older, their breeding competence improves.     

How social network structure affects decision-making in Drosophila melanogaster

Animals use a number of different mechanisms to acquire crucial information. During social encounters, animals can pass information from one to another but, ideally, they would only use information that benefits survival and reproduction. Therefore, individuals need to be able to determine the value of the information they receive. One cue can come from the behaviour of other individuals that are already using the information. Using a previous extended dataset, we studied how individual decision-making is influenced by the behaviour of conspecifics in Drosophila melanogaster. We analysed how uninformed flies acquire and later use information about oviposition site choice they learn from informed flies. Our results suggest that uninformed flies adjust their future choices based on how coordinated the behaviours of the informed individuals they encounter are. Following social interaction, uninformed flies tended either to collectively follow the choice of the informed flies or to avoid it. Using social network analysis, we show that this selective information use seems to be based on the level of homogeneity of the social network. In particular, we found that the variance of individual centrality parameters among informed flies was lower in the case of a ‘follow’ outcome compared with the case of an ‘avoid’ outcome.