Do females adjust brood sex ratio according to males’ genetic structures in a gregarious passerine,the vinous‐throated parrotbill Paradoxornis webbianus?

A growing number of bird species are known to have fine‐scale genetic structure during the breeding season, with relatives breeding in close vicinity. Such genetic structure often has fitness consequences for parents, and sex ratio theory predicts that females should respond adaptively when they determine offspring sex. We examined whether or not females allocate offspring sex adaptively in response to the local genetic structures as well as other biotic and abiotic factors in a population of the vinous‐throated parrotbill Paradoxornis webbianus, a small passerine with strong flocking habit and various genetic structures among neighbouring males during the breeding season. The average brood sex ratio of hatchlings (secondary sex ratio) did not deviate from parity. In addition, the observed brood sex ratio was independent of the fine‐scale genetic structure and other factors including breeding density, clutch size, laying date, parents’ quality, and the presence of extrapair paternity. Accordingly, we reject the hypothesis of adaptive sex allocation by female parrotbills in association with local genetic structure and other factors. Instead we conclude that despite the plausible benefits of biased sex allocation, this species determines brood sex ratio via random sex allocation with equal probability of male and female offspring.     

Habitat selection by dispersing yellow-headed blackbirds: evidence of prospecting and the use of public information

In migratory birds individuals may prospect for potential breeding sites months before they attempt to breed and should use the cues most predictive of future reproductive success when selecting a breeding site. However, what cues individuals use when prospecting and which cues are used in selecting a breeding site are unknown for most species. I investigated whether yellow-headed blackbirds (Xanthocephalus xanthocephalus) prospect for future breeding sites and whether they select breeding habitats based on food availability, male or female density, or the average number of young produced per female in the previous year. Although it is often assumed that migratory birds prospect for potential breeding sites at the end of the breeding season, I investigated this by recording all visits to sites early and late in the breeding season. I found that males and females who visited sites other than the site at which they bred were more likely to disperse than individuals only observed at the site where they bred, and that males and females were more likely to prospect late in the breeding season. Both food availability and density in year ^x were not predictive of the number of young per female in year ^x+1; however, the number of young produced per female at a site in year ^x was predictive of the number of young per female in year ^x+1. As expected, dispersers used the most informative cue, the number of young per female and moved to sites with a relatively high number of young per female. This study suggests that individuals prospect for potential breeding sites late in the breeding season when they can use information gathered from the reproductive success of other individuals (i.e., public information) to select a breeding site.     

Do common eiders nest in kin groups? Microgeographic genetic structure in a philopatric sea duck

We investigated local genetic associations among female Pacific common eiders (Somateria mollissima v‐nigrum) nesting in a stochastic Arctic environment within two groups of barrier islands (Simpson Lagoon and Mikkelsen Bay) in the Beaufort Sea, Alaska. Nonrandom genetic associations were observed among nesting females using regional spatial autocorrelation analyses for distance classes up to 1000 m in Simpson Lagoon. Nearest‐neighbour analyses identified clusters of genetically related females with positive lr values observed for 0–13% and 0–7% of the comparisons in Simpson Lagoon and Mikkelsen Bay, respectively, across years. These results indicate that a proportion of females are nesting in close proximity to more genetically related individuals, albeit at low frequency. Such kin groupings may form through active association between relatives or through natal philopatry and breeding site fidelity. Eiders nest in close association with driftwood, which is redistributed annually by seasonal storms. Yet, genetic associations were still observed. Microgeographic structure may thus be more attributable to kin association than natal philopatry and site fidelity. However, habitat availability may also influence the level of structure observed. Regional structure was present only within Simpson Lagoon and this island group includes at least three islands with sufficient driftwood for colonies, whereas only one island at Mikkelsen Bay has these features. A long‐term demographic study is needed to understand more fully the mechanisms that lead to fine‐scale genetic structure observed in common eiders breeding in the Beaufort Sea.     

Social organization and space use in California voles: seasonal,sexual, and age-specific strategies

We intensively monitored space use and movement in Microtus californicus over a 2-year period that included 1 year of high density (maximum 618/ha) and one of low (minimum 5/ha); historically this population has exhibited cycles of 2 or 4 years. Adults of both sexes dispersed at the start of the breeding season, culminating in the establishment of intrasexually exclusive territories. In females, these territories persisted throughout life, except that many young females recruiting during the breeding season established contiguous, overlapping, or adjacent home ranges with their mothers. This female philopatry explains the conclusion of previous workers that females of this species are non-territorial. In the dry (non-breeding) season, females had smaller ranges that often overlapped and were clustered. Adult males moved breeding territories at a modal interval of 6 weeks; this is consistent with their avoidance of inbreeding with philopatric daughters. Ranges overlapped 1–4 adult females at any one time, and a cohort of 7 long-lived males overlapped an average of 16.4 females during their tenure on the grid. The period of maximum overlap with adult females varied among individual males, and did not correlate with the time of maximum body weight. Ranges of males in the dry season overlapped extensively, with persistent associations among some individuals. In the lowdensity year, ranges of some adults failed to overlap intersexually. Juvenile males dispersed gradually between 3 and 13 weeks of age (half before 9 weeks), with some leaving after reaching sexual maturity; a few remained philopatric. Of juvenile females, 47% remained philopatric with the rest disappearing before 9 weeks of age. New understanding of vole social behavior, dispersal, and space use is achieved by focusing on the seasonal dynamics of spatial relationships among individuals with respect to age, sex, and relatedness.     

Agonistic and grooming behavior of captive crowned lemurs (Lemur coronatus) during the breeding season

Captive breeding of rare and endangered prosimians may be enhanced by an increased understanding of all aspects of their seasonal mating behavior. In this study, the agonistic and grooming behaior of captiveL. coronatus were studied during their annual breeding season. Between October and March, selected aspects of agonistic and grooming behavior of four male-female groups were recorded. Males initiated significantly more allogrooming than females. The frequency of this behavior pattern increased significantly in the weeks of estrus. Females performed significantly more agonistic behavior patterns than males. The mean frequency of agonistic interactions decreased significantly during the breeding season. In successfully reproducing groups males showed much less agonism towards females, than they did in unsuccessful groups. Inter-specific comparisons demonstrated that the patterns of agonistic interactions during the breeding season are very different among closely related species of lemurids. The conclusions drawn from this study are that captive breeding of crowned lemurs may be enhanced by keeping permanent multi-male, multi-female groups.     

A one night stand? Reproductive excursions of female roe deer as a breeding dispersal tactic

Breeding dispersal, defined as the net movement between successive breeding sites, remains a poorly understood and seldom reported phenomenon in mammals, despite its importance for population dynamics and genetics. In large herbivores, females may be more mobile during the breeding season, undertaking short-term trips (excursions) outside their normal home range. If fertilisation occurs, leading to gene flow of the male genome, this behaviour could be considered a form of breeding dispersal from a genetic point of view. Here, we investigated ranging behaviour of 235 adult roe deer using intensive GPS monitoring in six populations across Europe within the EURODEER initiative. We show that excursions are common from June to August among females, with 41.8 % (vs. 18.1 % of males) making at least one excursion. Most individuals performed only one excursion per season and departure dates for females were concentrated in time, centred on the rutting period, suggesting a link with reproduction. The distance females travelled during excursions was significantly greater than the site-specific average diameter of a male home range, while travel speed decreased once they progressed beyond this diameter, indicating search behaviour or interaction with other male(s) outside the resident male’s territory. Because adults are normally highly sedentary, the potential for mating with relatives is substantial; hence, we conclude that rut excursions could be an alternative tactic enabling females to avoid mating with a closely related male. To understand better the ultimate drivers at play, it will be crucial to explore the genetic causes and consequences of this behaviour.     

Estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in captive red wolves (Canis rufus)

This study investigated possible female-related causes for inconsistent success among reproductive pairs in the zoo-based red wolf (Canis rufus) population. Females (n = 13) at seven institutions were assessed for evidence of ovulation and normal reproductive cycles through the measurement of estradiol and progesterone metabolite excretion in feces. Fecal cortisol metabolites (FCM) were also measured. Factors potentially affecting FCM and/or estrous cyclicity were recorded, including exhibit status (on vs. off), reproductive history (proven vs. unproven), copulatory behaviors (ties observed: yes or no), pregnancy/parturition (pups or no pups produced), and translocation before the observed breeding season (yes or no). No differences were observed in baseline FCM between females housed on versus off-exhibit (p = .46) or between females producing pups and those who did not (p = .19). Baseline FCM were significantly lower among females observed in copulatory ties compared to females never observed in a tie (p = .04), and tended to be higher in females translocated before the breeding season compared to females in existing reproductive pairs (p = .11), and among historically unproven females compared to proven females (p = .11). All females evaluated had an endocrine profile indicative of ovulation and among the four females translocated to be paired with a new male before the breeding season, two had successful pregnancies, producing litters. Therefore, despite observed differences in baseline FCM among factors, estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in the zoo-based red wolf population.     

Floaters as intraspecific brood parasites in the grey starling Sturnus cineraceus

The breeding season of the grey starling Sturnus cineraceus is divided into two periods: the early and late breeding season. The birds that breed in each season are referred to as early and late breeders, respectively. In this study, the late breeders mainly consisted of new immigrants that did not breed in the early season. This suggested that these new immigrants were probably floaters in the early breeding season. Because intraspecific brood parasitism occurred frequently, it is possible that the parasites were floaters without nesting boxes. To check for the presence of floaters, two field experiments were conducted and floaters were captured with traps. With additional nesting boxes provided during the breeding season, all new boxes were quickly occupied by floaters from the period of incubation to hatching in the early breeding season, but were not occupied by floaters during the egg laying period of the late breeding season. The addition of boxes before the start of the breeding season significantly decreased the parasitic rate and number of parasitic eggs per nest. There was a positive correlation between the relative occupancy of nesting boxes and the parasitic rate. The removal of boxes again increased the parasitic rate. As for the capture of floaters with traps, the number of trapped birds per day was also related to the relative occupancy of nesting boxes. The floaters trapped between incubation and nesting periods of early breeders became the late breeders. Judging from these results, many floaters were present from the incubation to hatching periods of early breeders, and were probably intraspecific brood parasites.     

Age and size-dependent variation in the seasonal timing and probability of reproduction among mature female pumpkinseed,Lepomis gibbosus

Synopsis In this study, we used pumpkinseed,Lepomis gibbosus, populations in two east-central Ontario lakes to test for age and size-dependent effects on the probability and timing of reproduction of mature females. Pumpkinseed body size characteristics differed in the two lakes; Little Round Lake harbours a stunted population and Beloporine Lake does not. Age-class distribution of mature females was determined by a maturity assessment on fish collected just prior to spawning and at the mid-spawning period, combined with an early-season capture-mark-recapture survey. Spawning females were collected throughout the breeding season to assess age and size-related temporal trends, and to compare their age and size distribution with that of mature females at large. The proportion of age 2 females in Little Round Lake that actually spawned was considerably lower than the proportion of mature age 2 females at large. Furthermore, age 2 females that spawned in this lake did not do so until late in the breeding season. In contrast, the proportion of young/small females spawning in Beloporine Lake was comparable to the proportion of young/small mature females at large, and both small and large females spawned throughout the breeding season. Small mature females in Little Round Lake may have had no other option but to spawn late in the season because of their poor body condition. In Beloporine Lake, condition factor early in the breeding season in age 2–4 females was higher than that of Little Round Lake females, suggesting that limited energy reserves in the spring may have prevented young Little Round Lake females from early spawning. Our results show that the likelihood and timing of reproduction are both age and size-dependent in some populations. Small individuals that delay seasonal maturation and spawn late in the summer probably contribute little to the population due to the restricted growth and reduced overwinter survival of their progeny.To whom correspondence should be addressed     

Reproductive seasonality and nest-site differentiation in three closely related armoured catfishes (Siluriformes: Callichthyidae)

Synopsis Three sympatric, closely related armoured catfishes showed a similar, bimodal breeding season in coastal plain swamps in Suriname (South America). The bimodal pattern of reproduction inCallichthys callichthys,Hoplosternum littorale andHoplosternum thoracatum was correlated to the annual distribution of rainfall. Floating bubble nests were constructed throughout the period of swamp inundation (rainy season). Close inspection of the timing of reproduction ofH. littorale in northern South America revealed the relationship between reproduction and rainfall, but also unexpected differences in the length of the breeding season. Strong interspecific competition among the three species was probably avoided through differentiation of nest sites with respect to water depth, distance to the nearest tree, distance to the edge of the swamp, and cover above the nest. Nests ofH. littorale were built in herbaceous swamps, whileC. callichthys andH. thoracatum build their nests in swamp-forest. Nests ofC. callichthys were observed in extremely shallow water or in holes. Few nests of the three species were observed in canals. Over large parts of their geographical rangeC. callichthys andH. thoracatum are found in small rainforest streams. Several aspects of the reproductive ecology and behaviour of both species are probably related to the unpredictability of the stream habitat.     

Seasonal variation in reproductive traits of the oriental shrimp Palaemon macrodactylus (Crustacea: Caridea: Palaemonidae) in a non-native population

The magnitude of variations in reproductive traits of Palaemon macrodactylus females throughout a breeding season was studied in a non-native population at Mar del Plata harbor, Argentina. Fecundity, egg size, reproductive output, weight and elemental composition of eggs, and larvae were analyzed in females collected at the beginning, in the mid point, and near the end of a reproductive season and designated as early, middle season, and late females. The highest reproductive output was observed in early females, while the highest fecundity and egg volume occurred in middle season females. Eggs and larvae showed larger body mass in early than in late females. Embryos from early females contained and consumed more carbon during development than embryos from late females, and they also used part of the available nitrogen. Differences in reproduction were observed among the three groups of females. On the one hand, late females matured early but had a poor first reproduction, with few embryos and high egg loss; however, they had longer reproductive life and an enhanced reproductive output in the following season when they became early females. On the other hand, females collected at the midpoint in the reproductive season matured later and had the highest fecundity and egg volume. In addition, larvae with different characteristics resulted from each type of female and were presumably well adapted to the conditions prevailing at the moment they hatched. The extended reproductive period and the diversity of embryos and larvae produced may favor the invading ability of the species.     

Proximity structure in a captive colony of Japanese monkeys (Macaca fuscata fuscata): An application of multidimensional scaling

Spatial proximity was used to investigate the social structure of a group of 14 Japanese macaques (Macaca fuscata fuscata) living in Cavriglia Park (Arezzo, Italy). Instantaneous sampling was used to collect data. From April 1984 to March 1985, 273 hr of observation were accumulated. Time spent in proximity by any two monkeys was transformed into a similarity index. Two triangular matrices were created with these indices (one for the non-breeding and the other for the breeding season) and submitted to nonmetric multidimensional scaling (MDS). During the non-breeding season proximity proved closely related to hierarchical relationships and the existence of two real social classes was suggested. Tendency to loneliness was associated in this period with old age in females and low rank in both females and males. Moreover, socially stable versus socially unstable animals had different spacing patterns. Almost the same central-peripheral structure was outlined in both seasons, consistently with a stableoikia hypothesis for this group under these conditions. During the breeding season social organization was influenced by individual sexual interest. A male spacing pattern emerged, probably in correlation with female homosexuality, which played a preeminent role in the sexual context. The relative loneliness of sexually immature individuals was evident in this season.     

杂色山雀双亲差异性育雏策略

社会性单配制鸟类的配偶双方在抚育子代时常存在性别差异,不同鸟种的雌雄双亲往往采取不同的育雏策略。以杂色山雀(Sittiparus varius)为研究对象,2017年3—7月对繁殖巢箱进行录像监测,记录杂色山雀育雏期亲代投入情况。分析结果显示:1)双亲递食率在育雏前期(4—6日龄)无显著差异,而育雏后期(10—12日龄)雌性的递食率显著高于雄性。2)雌性亲鸟后期递食率较育雏前期显著增加;而雄性亲鸟育雏前期和后期递食率无显著差异。3)雌性递食率与自身喙宽呈极显著正相关,雄性递食率与双亲体征参数均无相关关系。总的来说,在育雏阶段,杂色山雀雌性亲鸟的递食率随着雏鸟的需求和自身身体质量发生调整,雌性在育雏后期递食率显著升高,而雄性亲鸟递食率无变化,这可能与育雏期双亲投入分工不同有关。     

Territorial behaviour in corn mice, <Emphasis Type="Italic">Calomys musculinus</Emphasis> (Muridae: Sigmodontinae), with regard to mating system

We studied territorial behaviour of Calomys musculinus, a promiscuous-polygynous species, in order to test the predictions that during the breeding period, home-range-owner females are more aggressive than home-range intruders and that males do not display territorial behaviour. At the core of the breeding season, we conducted 136 intrasexual and 66 intersexual encounters. The study was carried out in four 0.25-ha enclosures, each containing one independent population. We studied territorial behaviour utilising focal animal sampling to record behaviour. Encounters were conducted in a circular opaque arena (COA) near the home-range’s activity mathematical centre (AMC). Amicable behaviour was not observed in any of the 78 trials among females. The rates of aggressive and submissive behaviour per female–female encounters varied in relation to whether they were home-range owners or intruders, the former being aggressive, the latter submissive. So we could link these drives to the territorial behaviour of C. musculinus. This result fits well with the already known territoriality of C. musculinus during the breeding season. In contrast, the 58 intrasexual male encounters did not show direct aggressive interactions between them. The rates of the different behaviours between males did not vary in relation to whether they were home-range owners or intruders. In our study, which took place during the breeding period, C. musculinus males were nonterritorial, and they never exhibited aggressiveness towards females.     

Matrilineal kin clusters and their effect on reproductive success in the field vole Microtus agrestis

Kin dusters of philopatric females are thought to form the basicsocial organization of breeding females in various vole species.The spatial association between young breeding females and theirmothers was studied in five 2500–m² enclosures in naturalhabitats during mid- and late breeding season in summer 1992.The mothers (founder females) were introduced into the enclosuresin die beginning of the study in June, whereas the young breedingfemales were born within the enclosures. Matrilineal kinshipwas determined by using radionudides. In July-August, 58% ofyoung breeding females were philopatric, but 82% of the mother-daughterassociations broke up until August-September. Of the young femalesthat started to breed in August-September, only 12% were philopatricThus the kin clusters found were short Hved and few in numberduring the late breeding season. The reduction in the incidenceof the kin clusters coincided with an increase of populationdensity. The mean reproductive success of females breeding inkin clusters was better than that of those breeding separately.In addition, among the nonphilopatric females there was a positive,significant correlation between reproductive success and thedistance to the nearest unrelated founder female. Such correlationwas not found among the philopatric females.     

Brood mixing and reduced polyandry in a maternally mouthbrooding cichlid with elevated among-breeder relatedness

Uniparental maternal brood care often coincides with multiple paternity and single maternity of broods, possibly reflecting benefits of polyandry and costs of uniparental care. Genetic data from the maternally mouthbrooding cichlid fish Simochromis pleurospilus revealed the opposite pattern--low polyandry and allomaternal care. More than 70% of the investigated females had mated with a single male, and 14% of the females had unrelated fry in their broods. Broods with foreign fry were in the late stage of brood care, in which females guard free-swimming fry and recall the broods into their mouths for protection. With one exception, fostering females were related to their adopted fry at the level of first cousins (R(QG) > 0.12), but relatedness between fosters and adopted fry was not significantly higher than between fosters and fry tended by other females. Relatedness among breeders extended to the level of first-order relatives. Mean relatedness among contemporaneously breeding dams (R(QG) = 0.08) was significantly higher than among dams breeding in different seasons (R(QG) = -0.04), which suggests a temporal or spatial concentration of mouthbrooding relatives. Indeed, females sometimes brood in small groups. This behaviour may reduce brood predation but will increase the risk of brood mixing, which is possibly mitigated by low costs of brood care and indirect benefits accrued by relatedness among the breeders in the group. Remarkably, the apparent inbreeding potential did not give rise to bet-hedging polyandry or active avoidance of relatives, as half of the mated individuals were related at R(QG) > 0.13 and polyandry did not coincide with high within-pair relatedness.     

Fine-scale genetic structure and its consequence in breeding aggregations of a passerine bird

The pattern of fine-scale genetic structure in a population may reflect current biological processes of the species, such as natal dispersal, the breeding system and demography. We investigated the spatial distribution of nests and fine-scale genetic structure during two breeding seasons in a population of a weakly territorial, flock-living passerine bird, the vinous-throated parrotbill, Paradoxornis webbianus . Nest distribution was clustered. There were two peaks of egg laying within each breeding season, and spatial clustering of nests was more extreme during the second peak after controlling for breeding density. The patterns of genetic structure during the breeding season varied with parental sex and season. Genetic structure occurred during the second laying peak: males breeding within 200 m of one another at this time were significantly more closely related than males breeding farther apart. However, no apparent genetic structure was detected in males during the first laying peak or among females in either laying peak. These results reveal male-oriented kin affiliation during part of the breeding season in this species. Furthermore, juvenile recruitment into the winter flocks was positively related to this increased relatedness among males via kin affiliation. This study implies that fine-scale genetic structure during the breeding season could be a factor determining individual fitness and may play an important role in our understanding of the evolution of social systems.     

Intra-seasonal decline of clutch size in Lesser Snow Geese

Summary Different mechanisms proposed to explain the intra-seasonal decline in clutch size of Lesser Snow Geese (Anser caerulescens caerulescens) were tested at the La Perouse Bay colony, Manitoba, Canada. Ovary examination of females collected after laying revealed that the actual number of eggs produced per female decreased over the laying period. This finding eliminates nest-parasitism, partial clutch predation and renesting attempts as sufficient explanations for seasonal clutch size decline. Follicular atresia induced by reserve depletion was also rejected since its occurrence was similar among early and late nesters. The decline in clutch size was observed within age-classes, and therefore age effects on clutch size and laying date per se do not account for the observed relationship. Clutch size and laying date were respectively positively and negatively correlated with the amount of nutrient reserves in females at the onset of laying, and also covaried within individuals observed breeding in several seasons. Laying date repeatability was estimated at 0.22. It is postulated that the seasonal decline in clutch size results mainly from a positive feed-back of female's nutrient reserves on the hormones controlling ovary development. Hatching synchrony or shortness of the breeding season may be the ultimate factors responsible for the intra-seasonal clutch size decline in Lesser Snow Geese.     

Breeding suppression in the bank vole as antipredatory adaptation in a predictable environment

Summary In northern Fennoscandia, microtine rodent populations fluctuate cyclically. The environment of an individual vole can be considered to be predictable when the risks of predation and intra- and interspecific competition change with the cycle, such that both are high during the population highs of voles. The risk of predation is also high during the vole crash. After the crash, the vole population is characterized by low intra- and interspecific competition and low predation pressure. The main predators affecting voles during the crash are the small mustelids, least weasel and stoat. The density of these specialist predators declines drastically during the winter after the vole crash. We studied experimentally the impact of the perceived presence of stoats on the breeding and mating behaviour of voles. In a series of breeding experiments with bank voles,Clethrionomys glareolus, both old and young females suppressed breeding when exposed to the odour of stoats,Mustela erminea. The weights of females decreased in both experimental and control groups, but more among the voles under odour exposition. It seems that females actively avoided copulations under high predation risk and that breeding suppression is mediated by a change in female mating behaviour. There was no change in male behaviour or physical condition between the experimental and control treatments. An alternative mechanism for the observed breeding suppression could be the one caused by decreased feeding in females mediated with low energy intake which does not allow breeding. Regardless of its mechanism, delay of breeding should increase the probability of non-breeding females to survive to the next breeding season. The females surviving the crash should gain a strong selective advantage in a predator-free environment of the subsequent breeding season, which could explain the adaptive function of this antipredatory strategy.     

Annual reproductive activity of Caiman crocodilus fuscus in captivity

We describe the gonadal and abdominal fat storage cycles for a population of Caiman crocodilus fuscus kept in captivity at a breeding farm. The reproductive cycles of males and females are clearly seasonal. Vitellogenic follicles were observed in females year‐round; however, the follicular growth that produces the preovulatory follicles for the breeding season occurs in November–May (most of the dry season to the beginning of the rainy season). These months correspond with the presence of physiologically reproductive males. Oviposition takes place during the wet season (April–August) and the births occur at the end of this season (September–November). Fat storage was not related to reproductive activity, and did not vary by month or between sexes. Although environmental and hormonal conditions have been improved for these captive animals, they maintain a strongly seasonal reproductive cycle, historically fixed to oviposit in the most favorable period for nest construction and hatching during the rainy season. Zoo Biol 22:121–133, 2003. © 2003 Wiley‐Liss, Inc.