Temporal patterns of territory settlement and detectability in mated and unmated Nightingales Luscinia megarhynchos

In many bird species the sex ratio of adults is male-biased, which is likely to have consequences for the ecology as well as for the conservation of a species. For example, when some males remain unpaired in a population, there should be strong selection on behavioural traits that enhance pairing success. A surplus of males is also likely to have important implications for the interpretation of breeding bird survey data. In our study population of Nightingales Luscinia megarhynchos , about half of the males stayed unpaired, suggesting that the number of males encountered singing was greater than the number of breeding pairs. Furthermore, the detectability (the probability of encountering a male singing) of mated males was only two-thirds that of unmated males when censused in the morning or late in the breeding season. The relative detectability was more similar early in the season and during the twilight periods before sunrise and after sunset. Males that arrived earlier on the breeding grounds were more successful in attracting a mate than males arriving later. Some of the unmated males deserted their territories and prospected areas up to 4000 m distant, whereas others settled on the study site only late in the season and may actually have changed territories. We suggest that adult sex ratios and the time of the census should be taken into account when interpreting the results of breeding bird surveys.     

Cost of reproduction: a comparison of survival rates of breeding and non‐breeding male ortolan buntings

The cost of reproduction is expected to influence survival or future reproduction. Most previous studies have assessed cost of reproduction in relation to natural and experimental variation in number of offspring produced. The ortolan bunting Emberiza hortulana is a passerine bird species with biparental care, and the Norwegian population of the species has an extraordinarily skewed sex ratio with only about half of the males attracting a female, and therefore provides a rare opportunity to compare survival of males that have paired and bred with that of non‐breeders (unpaired males), which have not paid a cost of reproduction. Results showed that survival rates of paired (65.0%) and unpaired (64.2%) males did not differ. However, when comparisons were restricted to paired males that definitely had nestlings, their survival rate (76.8%) was significantly higher than that of unpaired males, and the same was the case when comparisons were further restricted to paired males that had offspring recruiting to the population the next year (76.8% survived). Males breeding successfully are likely to be a biased subset of high quality males. In analyses of a subset of males that had bred successfully when young, there was no difference in survival of paired and unpaired individuals when these males were older. In conclusion, breeding male ortolan buntings did not appear to pay a cost of reproduction in terms of reduced survival to the next year compared to non‐breeding males. These results may be explained by non‐breeding males also incurring extra costs during the breeding season, and that costs of reproduction are not shared equally among sexes in the ortolan bunting and other bird species with biparental care.     

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.     

Yaws disease in a wild gorilla population and its impact on the reproductive status of males

We evaluated the prevalence of skin lesions in a gorilla population in the Republic of Congo. The observed lesions were typical of yaws, a treponematosis described in gorillas and humans living in tropical regions. Among the 377 gorillas identified, 17% presented skin lesions, mainly on their faces. The worst cases presented physical handicaps because of the deep lesions. As in humans, lesions break out when individuals are young. Lesions were more prevalent among males than females above 8 years old. This sex-bias prevalence could result from the behavioral characteristics of males through a greater exposure to wounds. Lesions were also more prevalent in unmated adult males (either solitaries or those living in nonbreeding groups) than in males leading breeding groups. In the case of the latter, nonaffected and affected leading males had a similar number of infants and juveniles. Still, none of the leading males ever presented serious handicaps because of the skin lesions. This suggests that adult females could favor males without lesions. Finally, lesions were more prevalent among immature animals in nonbreeding groups than in breeding groups, suggesting that either young animals with lesions disperse earlier from their natal groups, or that the disease spreads faster in nonbreeding groups. Our results provide some insights into the spread of a disease in a wild population. Further studies are required to determine if the vigor of males affects the development of the disease and if affected individuals experience social discrimination inducing a negative impact on population dynamics.     

Male ornamentation and its condition-dependence in a paternal mouthbrooding cardinalfish with extraordinary sex roles

Cardinalfishes, in which males alone provide mouthbrooding, are likely candidates for sex-role reversal because of a higher potential reproductive rate for females than for males. In the gregarious cardinalfish, Apogon notatus, females establish breeding territories to form pairs prior to the breeding season. Within breeding pairs, females are more active in courtship and in attacks against conspecific intruders. Sex roles thus seem to be behaviorally reversed. The operational sex ratio is, however, male-biased because females suffer higher mortality than males and consequently males predominate in number in the adult population, leading to the prediction that males would be sexually selected. In the present study, morphological measurements showed that males had a protrudent lower lip that was expressed markedly during the breeding season. Field observation revealed that males with a longer and wider lip were preferentially accepted as a mating partner by territorial females. The male lip size positively correlated with their somatic condition, suggesting that the ornamental lip has evolved through indicator mechanisms of sexual selection. By contrast, females had longer fins than males, but these sexual dimorphisms were less pronounced and most of them were seasonally constant. These results support the prediction that sexual selection acts on males in this fish. Electronic Publication     

Reconnaissance for future breeding sites by spotted sandpipers

We studied the sex-role-reversed, polyandrous spotted sandpiper(Actitis macularia) from 1974 to 1990 in northern Minnesota,USA. After peak arrival of breeding birds and before peak departureat the end of the breeding season, there were many short-termvisitors (transients) to the study site. Stepwise discriminantfunction analysis (DFA) was used to determine the importanceof absolute sex ratio (males/female), sex of the transient bird,number of nests, and number of breeding males and females duringthe week of visit in predicting whether a visiting bird wouldreturn the following year. In addition, multiple regressionwas used to determine how much variability in the number oftransient birds returning in subsequent yearscould be explainedby annual values during the year of transience for numbers ofbreeding males and females, numbers of eggs laid and hatched,and absolute sex ratio. Annual recruitment of foreign adultsranged from 1 to 20 birds, of which 0–56% were seen visitingin previous years. Female recruits were more likely than malesto have been observed previously as transients. Twenty-two chickshatched at our study site returned and bred for the first timemore than 1 year after hatching. Of these, 9 (41%) were seenas transients between the year of hatch and breeding. The DFAshowed that transient females returned more often than transientmales and that the number of transients returning in subsequentyears was positively associated with the absolute sex ratioduring the week visited. When the sexes were analyzed separately,none of the weekly variables significantly discriminated femalereturn, but sex ratio was positively associated with male return.Regression showed that the number of transient birds returningin subsequent years was positively associated with the numberof male breeders at our study site during the year a bird visited.Percentage return the year after transience was positively associatedwith the number of eggs laid at our study site during the yeara bird visited. When sexes were analyzed separately, the higherthe number of female breeders during the year a bird visited,the greater the number of males returning in subsequent years,and greater numbers of breeding males were positively associatedwith transient female return. Based on our results, we suggestthat transient birds were searching for better breeding areasfor future breeding and that intrasexual competition made thisinformation more important to females than to males.     

Notoedric mange in western gray squirrels from Washington

From February 1998 to July 1999, 65 western gray squirrels (Sciurus griseus griseus) were trapped at three sites in Klickitat County, Washington (USA) as part of a home range and habitat use study. No squirrels (0/9) with mange lesions were identified in the initial trapping session (February and March 1998). During all subsequent trapping sessions (August 1998 through July 1999), squirrels with lesions consistent with notoedric mange, caused by the mite Notoedres centrifera (douglasi), were captured or recaptured at all three study sites. The diagnosis was confirmed by histopathology and examination of mites obtained from skin scrapings from two affected squirrels. Of the 56 squirrels captured from August 1998 to July 1999, 33 (59%) had characteristic mange lesions, and 14 (42%) affected squirrels died directly of mange or of secondary complications of mange. Only four breeding females of 22 radio-collared animals (males and females) in the study population were known to have survived the mange outbreak (12 died, 6 missing). Factors potentially contributing to this mange outbreak include a mast crop failure in the fall of 1998 and transmission of mites from animial to animal during trapping and processing sessions.     

Senescence and carryover effects of reproductive performance influence migration,condition, and breeding propensity in a small shorebird

Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animal's breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus ), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; β_sex = ?0.21, 95% CI: ?0.38 to ?0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.     

Ecological and Phylogenetic Effects on Song Sharing in Songbirds

As a consequence of vocal learning, the songs of male songbirds often vary geographically. We examined three proximate hypotheses that predict variation in the incidence of local song sharing among species: the annual cycle, breeding season duration, and epiphenomenon hypotheses. To test these hypotheses, we compiled data from the literature on local song sharing, annual cycle, breeding location isophane (an index of breeding season duration), repertoire size, and phylogenetic relationships of 65 populations in the family Fringillidae. Mapping characters on the phylogenetic tree revealed that local song sharing, migratory status, and breeding location isophane were randomly distributed on the phylogeny. Breeding isophane and migratory status were themselves correlated and had significant effects on the probability of sharing local songs. As predicted by the annual cycle and breeding season duration hypotheses, males in sedentary populations and populations breeding at low isophanes were more likely to share local songs. In subsets of the data, the annual cycle hypothesis received more support than did the breeding season duration hypothesis. Neither hypothesis explained more than 17% of the variation in the incidence of song sharing, and we suggest that detailed information on song function, male dispersal, and constraints on the timing of song learning will be needed to better predict the occurrence of local song sharing.     

Costs of reproduction in male lizards, Sceloporus virgatus

Models of life history evolution typically assume a balance between the benefits of current reproductive activity and the costs to future reproductive success or survivorship, but empirical studies often find positive correlations between such components of fitness in undisturbed animal populations. I examined possible survivorship costs of reproduction in free-ranging male lizards, Sceloporus virgatus , and found that males with low levels of mating success were less likely to survive to the following breeding season. I also investigated two possible indicators of reproductive effort, increase in ectoparasite load and decrease in body weight during the breeding season. Levels of parasitism with trombiculid mites at the end of the breeding season were not associated with any measure of fitness or body condition (mating success, survivorship to the following year, relative weight loss). Yearling males (which have low levels of mating success) usually gained weight during the breeding season, while older males generally lost weight during this period. This suggests that young males may have postponed reproduction in favor of body growth and that seasonal weight loss of older males might reflect reproductive effort. Within the group of older males, individuals with the highest levels of mating success did not have high levels of either weight loss or mortality. Mate guarding behavior, an alternative to the aggressive territorial behavior typical of many lizard species, may allow certain males to obtain mates without expending large amounts of energy or exposing themselves to great mortality risks.     

Seasonal variation in male alternative reproductive tactics

Genetic parentage analyses reveal considerable diversity in alternative reproductive behaviours (e.g. sneaking) in many taxa. However, little is known about whether these behaviours vary seasonally and between populations. Here, we investigate seasonal variation in male reproductive behaviours in a population of two‐spotted gobies (Gobiusculus flavescens) in Norway. Male two‐spotted gobies guard nests, attract females and care for fertilized eggs. We collected clutches and nest‐guarding males early and late in the breeding season in artificial nests and used microsatellite markers to reconstruct parentage from a subset of offspring from each nest. We hypothesized that mating, reproductive success and sneaking should be more prevalent early in the breeding season when competition for mates among males is predicted to be higher. However, parentage analyses revealed similar values of mating, reproductive success and high frequencies of successful sneaking early (30% of nests) and late (27% of nests) in the season. We also found that multiple females with eggs in the same nest were fertilized by one or more sneaker males, indicating that some males in this population engage in a satellite strategy. We contrast our results to previous work that demonstrates low levels of cuckoldry in a population in Sweden. Our results demonstrate marked stability in both the genetic mating system and male alternative reproductive tactics over the breeding season. However, sneaking rates may vary geographically within a species, likely due to local selection influencing ecological factors encountered at different locations.     

Song-type matching between neighbouring song sparrows

In our study population, neighbouring song sparrows typically share two or more of their 6-10 song types. In an earlier experiment, we found that established neighbours typically reply to playback of neighbour-shared song with a different song they share with that neighbour ('repertoire matching'), rather than with the same song ('type matching') or with a nonshared song. In the present experiment, we considered the hypothesis that type matching is a threat or warning signal (Krebs et al. 1981, Animal Behaviour, 29, 918-923). We tested the specific prediction that a bird is more likely to type-match early in the breeding season when territory boundaries are new and still unstable, and more likely to repertoire-match later in the season, once those boundaries have become well established. Birds were played a shared song of a new neighbour once early (April) and again late (June) in the breeding season. As predicted, early in the season birds usually type-matched the playback (73% of the trials) but late in the season they type-matched only rarely (18%); birds never replied (early or late) with a nonshared song type. Copyright 2000 The Association for the Study of Animal Behaviour.     

Age,condition and dominance‐related sexual ornament size before and during the breeding season in the black grouse Lyrurus tetrix

Male ornaments function as honest cues of male quality in many species and are subject to intra‐ and intersexual selection. These ornaments are generally studied during peak expression, however their size outside the breeding season may determine ultimate ornament size and costliness, and as such reproductive success. We investigated whether male black grouse Lyrurus tetrix eye comb size was related to age, condition and measures of male dominance before and during the breeding season. Total combined eye comb size began to increase ~70 d before the start of the breeding season. Adult males (aged ≥ 2 yr old) had consistently larger eye combs than younger males (1 yr old) both before and during the breeding season. Heavier and more dominant adult males (attending the lek more frequently and successfully reproducing) had larger eye combs. For younger males, those that were heavier had larger eye combs. Additionally, males that spent more time on the lek showed increased eye comb size as the breeding season approached. Overall we find that ornament size is positively related to dominance and condition before and during the breeding season. Since dominance is accrued through year‐round interactions in many species, the ability to maintain larger signals over prolonged periods, including outside of the breeding season, is likely to be beneficial for adults. For younger males, it is likely that they cannot sustain or are constrained from producing larger eye combs over long periods of time. They therefore prioritise growth of their ornaments later, and according to the amount of time they spend on the lek.     

Avian responses to forest fragmentation during the breeding and non-breeding seasons

Forest fragmentation represents a threat to several bird species worldwide. Several factors can change across seasons (e.g. bird perception of the landscape, weather conditions, biotic interactions), which can modify the response of bird populations to forest fragmentation. However, most studies have been conducted only during the breeding season. Here we assessed the relationship between forest fragmentation (patch area and patch isolation) with population abundances of resident species during both the breeding and the non-breeding seasons. Bird population abundances (all species in the community, subsets of forest and habitat generalist species and for individual species) were estimated across a gradient of area-isolation in a semi-arid forest in Cordoba, Argentina. Population abundance of the overall avian community and of the subset of forest species declined with patch area reduction independently of the season. By contrast, the subset of habitat generalist species was not affected by patch area reduction or by the increase in patch isolation, either during the breeding or during the non-breeding season. When the analyses were carried out for individual species, we found four forest species and one habitat generalist species whose responses (the relationship between population abundance and patch area or with isolation) were different between breeding and non-breeding seasons. The negative effects of forest fragmentation were found mainly during the breeding season. Our results suggest that reduction of patch area may lead to a reduction of more than 65% of the population abundance of forest bird species, during both the breeding and the non-breeding season. Therefore, there is an urgent need to conserve large forest patches within the region as irreplaceable elements for the conservation of populations of several species.     

灰椋鸟身体大小和内脏器官形态的两性差异

鸟类性二态现象广泛存在,比如身体大小、羽色等,性二态很可能是自然选择和性选择共同作用的结果.为了探索和更好地了解雀形目鸟类身体大小性二态的进化,在2019年繁殖季节早期研究了灰椋鸟(Sturnus cineraceus)野外种群身体大小和内脏器官形态的两性差异.结果表明,除嘴宽外,其他身体特征参数均雄性显著大于雌性,表...     

Seasonal and age-related changes in blood parasite prevalence in Dark-eyed Juncos (Junco hyemalis, Aves, Passeriformes)

We determined seasonal changes in blood parasite infections in a free-living population of Dark-eyed Juncos (Junco hyemalis) breeding in interior Alaska (65 degrees N; 148 degrees W). The common parasites found in blood smears were Leucocytozoon fringillinarum (56%), Trypanosoma avium (33%), and Haemoproteus fringillae (9%). In males, parasite prevalences were relatively high at arrival on breeding grounds and increased during the breeding season. Intensity of infection with Leucocytozoon also increased between spring and summer, and then decreased at the time of migration (September). This decrease did not occur in adult females. Elevated prevalences during the breeding season probably reflected the addition of new cases via vector activity to positive status resulting from spring relapse. We observed neither an association between parasite species nor a consistent relationship between parasite intensity and body condition. To further study relationships between reproductive system activity and parasite infections, we compared prevalences in adult males that were undergoing their first cycle of gonadal development and regression (males in their second calendar year, or SY) with those of older males (males in their third or more calendar year, i.e., after-second-year males or ASY). Circulating testosterone concentrations declined in both groups between arrival on breeding grounds (end of April-early May) and the end of the reproductive period (July), and they were higher in May in ASY than in SY males. At the peak of the breeding season (June), ASY males also had a higher parasite prevalence than SY males. This difference may have resulted from immunosuppressive effects of gonadal hormones and/or from behavioral differences between SY and ASY males such that older males were exposed to more insect vectors than younger males. .     

First report of a hawfinch (Coccothraustes coccothraustes) parasitized by Harpirhynchus nidulans in the Iberian Peninsula

Some avian Harpirhynchidae mites live under the skin and develop cutaneous cysts. Despite the obvious lesions that these parasites can produce, little is currently known about the behavioural disturbances that cyst-forming mites may cause in infected wild birds. We report an infection by Harpirhynchidae mites in a hawfinch (Coccothraustes coccothraustes) in southeast Spain. The bird was easily captured due to its inability to fly. During clinical examination it was found to have multiple severe traumatic injuries, possibly due to a blow or a fall, as result of which the bird was euthanized. At necropsy, the hawfinch was found to be in good body condition. Two yellowish and friable mite-filled cysts were detected in the subalar region of both wings. Mites were morphologically identified as Harpirhynchus nidulans, and histological analysis of the cystic lesions was also performed. This is the first time that the occurrence of a hawfinch infected by H. nidulans in the Iberian Peninsula has been reported.     

秦岭羚牛中独栖现象的初步观察

在群栖的秦岭羚牛种群中,存在着少数单独活动的羚牛, 称为独牛。野外见到独牛50只次, 占见到羚牛总数的4.59 %。独牛中有老年雄性个体、青壮年雄性个体、雌性个体、亚成体和幼仔。在繁殖季节独牛出现的次数最多, 其中大部分是雄性个体, 也有雌性个体。与羚牛的四川亚种不同, 在秦岭亚种中很少见到公牛集群的现象。羚牛种群中独牛的形成主要与繁殖有关, 同时还与疾病及防御迁移有关。独牛在不同季节、不同生境内均可见到 , 绝大多数老年独牛活动区域的海拔高度低于集群的羚牛活动的高度。老年独牛在离群活动后,其活动节律与群体中的雄牛有一定的差异, 这种差异在夜间的活动时间和活动率方面表现得更加明显。     

Delayed plumage maturation increases overwinter survival in North Island robins

Many bird species show delayed plumage maturation (DPM), retaining sub-adult plumage until after their first breeding season. Most explanations assume that DPM increases fitness over the breeding season. However, unless birds undergo a full moult before breeding, DPM could also be an adaptation to increase survival over the previous winter. The winter adaptation hypothesis has never been tested owing to the difficulty of measuring overwinter survival. We experimentally tested this hypothesis in North Island robins (Petroica longipes) using a closed island population where we could accurately estimate survival. The experiment involved dyeing 41 juveniles to mimic adult males, and comparing their survival with 41 control juveniles treated with the same peroxide base minus the pigment. The population was monitored with a series of resighting surveys, and mark-recapture analysis used to estimate overwinter survival. Survival probability was estimated to be 10% for dyed birds versus 61% for control birds in 2001, and 29% for dyed birds versus 40% for control birds in the winter of 2002, supporting the winter adaptation hypothesis for DPM. Access to suitable habitat is the key factor limiting juvenile survival in this population, and the locations where dyed juveniles were sighted suggest that they were often excluded from suitable areas.     

Patterns of territory settlement and consequences for breeding success in the Northern Wheatear Oenanthe oenanthe

We examined the pattern of territory settlement and its consequences for breeding success in the Northern Wheatear Oenanthe oenanthe on Bardsey Island, Wales, during the breeding seasons of 1991-93. Males returned earlier than females, and older males returned earlier than first-year breeders. Although their boundaries shifted between years, the general location of territories was consistent during the three-year study. There was a high degree of fidelity to area and territory between years for both sexes. The order of territory settlement, from which a territory rank was calculated, was highly consistent for males between years irrespective of individual settlement patterns and territory fidelity. Patterns of territory settlement were less predictable for females, although there was a significant correlation between the mean territory ranks of paired males and females. There was a male-biased sex ratio in each year, and between 5% and 26% of males remained unpaired throughout the breeding season. Male mating status and breeding success were dependent on arrival date, territory rank and breeding density. Early-arriving, usually older, males were able to settle on territories first and were more likely to pair, while later-arriving individuals were more likely to remain unmated. These effects were consistent between years, and consequently territories could be classified as either preferred (accounting for proportionately more breeding attempts) or non-preferred. Territory quality as opposed to individual quality appeared to explain much of the variation in breeding success, and both sexes benefited by breeding on preferred territories through enhanced breeding success and an increased probability that their offspring would be recruited to the population.