Breeding Interval Research Articles

Breeding ecology, population size and nest site preferences of Red-billed Tropicbirds at St Helena, South Atlantic Ocean

ABSTRACT We describe the population size and breeding ecology of the Red-billed Tropicbird, Phaethon aethereus, a poorly studied pantropical seabird, at St Helena, South Atlantic. The population size of 81–246 pairs and 272–564 individuals identifies the study population as the largest colony of Red-billed Tropicbirds in the South Atlantic, but also an internationally important part of the global population. We estimated the survival from laying to fledging of 158 nests between 2004 and 2017 at only 33%, among the lowest values reported globally for the species. Most nest failures occurred during incubation, with predation identified as the predominant cause of fledging failure. Intervals between breeding attempts were longer after successful nesting attempts than failed attempts. Previous breeding interval and nest cavity fidelity further influenced the interval between breeding attempts, while the presence of replacement clutches did not. Multiple nest site and cavity characteristics were important predictors of cavity use, nest site selection and productivity. Management options for reducing mammalian predators to ensure the long-term viability of this important population at St Helena are discussed.

Novel insights into the reproductive strategies of wild Chinese sturgeon (Acipenser sinensis) populations based on the kinship analysis

Understanding the reproductive strategy of an organism is important in conservation ecology as it directly affects the population performance under changing environmental conditions. Chinese sturgeon (Acipenser sinensis) are the largest anadromous fish in the Yangtze River, China. Currently, the species has only one spawning ground and has failed to spawn in recent years, leading it to the brink of extinction. To develop effective conservation measures, a further understanding of its reproductive strategy is needed. In our study, we conducted kinship analyses by using mitochondrial and microsatellite DNA data from 216 wild juveniles collected over nine years (2006−2013, 2015) to understand the mating system, breeding interval, effective number of breeding adults, and reproductive success. The results from these analyses suggested polygynandry, with some parents contributing up to eight half-sibling juvenile genotypes. Although the spawning ground was restricted to a limited area, genetic diversity was maintained at a relatively high level (observed heterozygosity from 0.698 to 0.787 and expected heterozygosity from 0.763 to 0.787) and inbreeding coefficients in each year-class ranged from −1% to 9% (low to modest detrimental effects on offspring). A parental inference analysis revealed that Chinese sturgeon have a breeding interval of 2–6 years, indicating that it has the potential to feed, accumulate nutrition in the ocean, and then migrate back to the Yangtze River for iteroparous reproduction. The annual effective number of breeders in the Yangtze River ranged from 14 to 161 during the study period, and it decreased by 62.1% from the 2011−2014 year-classes. This sharp population decline likely contributes to the reproduction failure. However, the ratios of effective to census population size (Ne/Nc) were all larger than 0.20 after the 2010 year-class, indicating relatively even reproductive success. Based on these results, a suggested approach to protect this species is to restock parent fish to increase the reproductive stock size and optimize the discharge of the Three Gorges Dam to reduce the unsuitable hydrological conditions and rehabilitate spawning ground habitats.

Estimating contemporary migration numbers of adults based on kinship relationships in iteroparous species.

This paper describes the development of estimators for the contemporary migration number and rate of adults between two populations in iteroparous species. The proposed estimators are based on known half-sibling (HS) and/or parent-offspring (PO) relationships observed between populations across breeding seasons. The rationale is that HS and PO pairs exhibit information about the occurrence frequency of parental movements during the breeding interval. The proposed method allows for variance in the average number of offspring per parent within and between populations. In addition, coupled with the PO pairs found within the population, the estimators can be obtained using only genetic data. Generally, a sample size representing the square root of the population size is required to obtain meaningful migration information. We describe a detailed evaluation of the performance of the proposed estimators by running an individual-based model, and the results provide guidance regarding sample sizes to ensure the required accuracy and precision. In addition, given that there are few effective methods to estimate adult movement (especially when populations cannot be genetically distinct), we discuss the usefulness of the proposed kinship assignment method in terms of conservation biology and wildlife management.

Astragalus membranaceus Additive Improves Serum Biochemical Parameters and Reproductive Performance in Postpartum Dairy Cows.

The purpose of the study was to assess the recovery, immune function, and breeding efficiency of postpartum dairy cows fed Astragalus membranaceus (AM) as a feed additive. The experiment used a completely randomized design. Cows were randomly assigned to two groups: (1) Control group fed total mixed ration (TMR; CON group, n = 15); (2) AM group fed TMR and AM (AM group, n = 15). The AM group was fed 675 g/day. The experimental results showed that compared with the CON group. The breeding interval of the AM group of dairy cows had a tendency to shorten (0.05 < p < 0.1). Plasma viscosity (PV), Plasma fibrinogen (FIB), the red cell aggregation index (TRCAI), Calcitonin (CT), Immunoglobulin M (IgM), and Luteinizing hormone (LH) results of AM group showed a time-treatment interaction (p < 0.05). Furthermore, the result of the study revealed that feeding AM as feed additives to dairy cows during the postpartum period had positive effects on wound recovery, immune function, endocrine regulation, and breeding efficiency.

Genome-Wide Association Studies in Indian Buffalo Revealed Genomic Regions for Lactation and Fertility.

Murrah breed of buffalo is an excellent dairy germplasm known for its superior milk quality in terms of milk fat and solids-not-fat (SNF); however, it is often reported that Indian buffaloes had lower lactation and fertility potential compared to the non-native cattle of the country. Recent techniques, particularly the genome-wide association studies (GWAS), to identify genomic variations associated with lactation and fertility traits offer prospects for systematic improvement of buffalo. DNA samples were sequenced using the double-digestion restriction-associated DNA (RAD) tag genotyping-by-sequencing. The bioinformatics pipeline was standardized to call the variants, and single-nucleotide polymorphisms (SNPs) qualifying the stringent quality check measures were retained for GWAS. Over 38,000 SNPs were used to perform GWAS on the first two principal components of test-day records of milk yields, fat percentages, and SNF percentages, separately. GWAS was also performed on 305 days’ milk yield; lactation persistency was estimated through the rate of decline after attaining the peak yield method, along with three other standard methods; and breeding efficiency, post-partum breeding interval, and age at sexual maturity were considered fertility traits. Significant association of SNPs was observed for the first principal component, explaining the maximum proportion of variation in milk yield. Furthermore, some potential genomic regions were identified to have a potential role in regulating milk yield and fertility in Murrah. Identification of such genomic regions shall help in carrying out an early selection of high-yielding persistent Murrah buffaloes and, in the long run, would be helpful in shaping their future genetic improvement programs.

Studies of management effects on fertility of purebred and crossbred exotic gilts in two breeding farms at NSUKKA, Nigeria

Sixty healthy gilts comprising 15 Landrace (LR), Large White (LW} and LW x Hampshire (HS) breeds respectively, were selected from Federal Government (FG) breeding center at Okpuje near Nsukka and University of Nigeria Nsukka (UNN) farms. They were bred through 4 years (1993 to 1996) during which management effects on fertility were assessed. Gilts were mated on observation of third cyclic oestrus and at subsequent postweaning oestrus. Fertility was assessed from vital reproductive traits due to dams and offsprings. All gilts had successful first and second parity breeding. Thereafter there were increasing cases of abortion and anoestrus particularly among purebred groups in FG farms. Generally, 8 (53.3%), 6 (40.0%), 10 (66.7%) and 13 (86.7%) out of 15 dams in respective groups could attain fifth parity within four years. Both groups exhibited long breeding Intervals (ranging from 192-268 days). Purebred LW and LR offspring had slightly lower mean litter size of 8.5 ± 1.8 and 8.8 ± 1.5 compared with 9.5 ± 0.9 and 9.7 ± 1.4 (P&lt;0.05) for LW x LR and LW x HS crossbred counterparts respectively, Birth and weaning weights and daily weight gain were similarly lower for purebred than crossbred offsprings. Attendant mortality rates of 13.1% and 15.7% for the former were significantly higher than 9.8% and 10.1% (&lt;O.05) obtained for the latter offsprings respectively. The FG farm was more understocked, underutilized and undermanaged than the UNN farm probably because of inconsistencies arising from administrative bureaucracy. Consequently constraints are identified for improvement through efficient resources inputs, staff incentives and application of modern strategic management techniques recommended for tropical environment. Further research into stocking Hamphsire crossbred pigs in the tropics is suggested, in view of its favourable performance.

Socio-ecological factors shape the opportunity for polygyny in a migratory songbird

Abstract Why females pair with already mated males and the mechanisms behind variation in such polygynous events within and across populations and years remain open questions. Here, we used a 19-year data set from a pied flycatcher (Ficedula hypoleuca) population to investigate, through local networks of breeding pairs, the socio-ecological factors related to the probability of being involved in a polygynous event in both sexes. Then, we examined how the breeding contexts experienced by individuals shaped the spatial and temporal separation between broods of polygamous males. The probability of polygyny decreased with the distance between nests. Indeed, secondary females were often close neighbors of primary females, although the distance between both nests increased slightly with increasing synchrony between them. The probability of polygyny was also related to the breeding time of individuals because early breeding males were more likely to become polygynous with late-breeding females. Throughout the season, there was substantial variation in the temporal separation between primary and secondary broods, and this separation was, in turn, related to the breeding asynchrony of the polygamous males (in the primary nest) relative to the neighbors. Polygynous males that bred late relative to their neighbors had a short time window to attract a second female and, thus, the breeding interval between their primary and secondary broods was reduced. Overall, the spatial proximity between polygynous males’ broods and, if the opportunity existed, their temporal staggering are compatible with a male strategy to maximize paternity and reduce the costs of caring for two broods, though the effect of female’s interest, either primary or secondary, cannot be fully ruled out. We highlight that a comprehensive assessment of the breeding contexts faced by individuals is essential to understand mating decisions and reconcile the discrepancies raised by previous work on social polygyny.

Survival and breeding interval of an endangered marine vertebrate, the leatherback turtle Dermochelys coriacea, in French Guiana

In the context of global change, endangered species such as sea turtles undergo strong population dynamics changes. Understanding demographic processes inducing such changes is critical for developing appropriate measures for conservation and management. Nesting females of the French Guiana population of leatherback sea turtles Dermochelys coriacea represented 40% of the world’s total in 2001; today, they represent only 10%. Here, we analyze data from the long-term monitoring program of leatherbacks in French Guiana, based on 28 yr of capture-mark-recapture data from 46051 individuals in northwestern French Guiana. We used multievent models (multistate capture-recapture models with state uncertainty) to represent the main peculiarity of the life cycle, intermittent reproduction, and to take advantage of the use of several different types of marks to account for mark loss and incomplete detection. The average annual adult survival probability (mean ± SE) 0.789 ± 0.009 is low compared to published estimates for this species. By combining the estimates of departure and return probabilities, we provide an estimate of the interval among laying seasons equal to 2.777 ± 0.118 yr, which matches previous findings. Taking survival into account, this interval translates into an average of 1.704 ± 0.034 further reproductive seasons for an adult female having just bred, which is remarkably low compared to other long-lived vertebrates. The representation of the life cycle and mark loss in our models provides a sound structure for broader and richer analyses to extract biological information from marked individuals and offers an invaluable source of demographic information on leatherbacks, a species for which only a small segment of the population is accessible to intermittent sampling.

Follicular wave synchronization prior to ovum pick-up

Among the reproductive biotechnologies, in vitro embryo production (IVEP) is an important tool for multiplying genetic material of superior merit. Recently, the number of embryos produced and transferred in vitro became significantly higher than that produced in vivo worldwide. In this context, the enhancement was attributable to ovum pick-up (OPU). With the advent of genomic technology, shortened breeding intervals, and increased selection accuracy, IVEP has attracted increasing attention for commercial use. The IVEP technique is well-established, but the embryo production rate has reached a plateau at 30–40%. Despite constant advances, the OPU/IVEP programs face some challenges that hinder the efficient application of the technique. Previous studies have shown that the quantity and quality of aspirated oocytes are essential factors for successful IVEP. This paper presents a brief overview of alternatives that can be employed to improve the process-seeking methods that assist in the recovery of better-quality oocytes and higher competence in OPU to improve embryo production. These strategies include using follicular wave synchronization prior to OPU, employing the influence of antral follicle populations, using the pre-OPU gonadotrophic stimulus and applying non-hormonal methods for selecting female donors.

Herd and environmental determinants of reproductive performance in Swedish dairy herds, 2001–2009

This was a retrospective cohort study of Swedish dairy herds. Summary measures of production and reproductive performance, details of soil, moss mineral concentrations, and temperature and rainfall measurements at each herd location were available for the period September 2001 to August 2009. A Bayesian mixed-effects regression model including spatial and non-spatial heterogeneity terms was developed to quantify associations between hypothesised explanatory variables and mean herd breeding interval, defined as the difference between mean calving to last service interval and mean calving to first service interval for each fiscal year.Mean herd breeding intervals were shorter in herds with greater than 80% Swedish Red Cattle, herds with lower mean age at first calving, herds comprised of older cows and in larger herds. None of the soil composition or moss mineral concentration estimates were associated with mean herd breeding interval and the effect of temperature and rainfall on mean herd breeding interval was small. We conclude that environmental conditions (soil composition, moss mineral concentrations, environmental temperature and rainfall) had relatively minor effects on dairy herd reproductive performance in Sweden between 2001 and 2009.

Management practices associated with reproductive performance in Holstein cows on large commercial dairy farms

As a result of the increase in herd size and the intensification of production, the complexity of reproductive management has been growing in dairy herds. The aim of our study was to examine the associations of management practices and reproductive performance in Holstein cows on large commercial dairy farms. Management practices applied to cows were surveyed between 22 May and 6 November 2015 in 34 large Holstein-Friesian dairy herds in Hungary. Individual data of 23 784 cows that calved between 1 January 2014 and 31 December 2014 in the surveyed herds were gathered. Associations between the management practices and the reproductive parameters were analyzed by mixed effects models. Regarding heat abatement we found that ventilation with sprinklers was associated with the shortest breeding interval (P<0.01), the shortest calving to conception interval (P<0.01), and the highest odds of being pregnant by 200 days in milk (P<0.01). Solely ventilation showed similar (P>0.05) results to lack of heat stress protection. It was also revealed, that lack of a well-established voluntary waiting period (VWP) or a VWP shorter than 50 days was associated with less days to first service (P<0.01), shorter breeding interval (P<0.01) and calving to conception interval (P<0.05), as well as higher odds of carrying a calf by 200 days in milk (P<0.01) compared with those using a VWP of at least 50 days. Those farms that applied transrectal ultrasonography were more likely to use ventilation with sprinklers (P<0.05), hormonal synchronization (P<0.01) and to perform early pregnancy diagnosis followed by pregnancy recheck (P<0.05). The application of transrectal ultrasonography with one of the aforementioned practices was associated with reduced days to first service (P<0.05), shorter breeding interval (P<0.05) and higher odds of pregnancy at 200 days in milk (P<0.05). Our study highlights the management practices most closely related to improved reproductive performance, which are, therefore, suggested to be applied on dairy farms, considering the local circumstances of the individual farms.

Reproductive Parameters of Female Long- finned Pilot Whales (Globicephala melas edwardii) from the Southwestern Atlantic.

Soto Florencia Anabella, Grandi María Florencia, García Néstor Aníbal, Crespo Enrique Alberto, and Dans Silvana Laura (2017) Mass strandings represent a valuable source of information, especially when it comes to difficult-to-access pelagic species, such as Globicephala melas edwardii. We collected reproductive organs from 27 female pilot whales stranded in Caleta Malaspina, Chubut, Argentina. Our main objective was to analyze reproductive parameters of female long- finned pilot whales in the southern hemisphere. To achieve this, we studied age and reproductive status in order to approximate age and body length at sexual maturity, breeding interval, and fertility of this subspecies. The maturity state was determined by recording different ovulation bodies obtained from histological sections and by assessing the presence of milk in the mammary glands and a fetus, and we concluded that 5 of the females were immature and 22 were mature females. Finding mature females in different reproductive states (resting, in lactation, pregnant, or pregnant and in lactation) along with the great variety of fetus sizes would indicate that copulation and birth are not governed by seasonality. Age at sexual maturity was 8 years old and length at sexual maturity would reach 365.50 cm. The annual pregnancy rate was constant with age for mature females at 0.41 ovul / year, with a breeding interval of 2.4 years. The average fertility varied between 0.19 and 0.21. All the parameters are within the estimated range for females of the North Atlantic subpopulation, except for the breeding interval, which was significantly lower than estimates for the northern subspecies. This study could be limited because all individuals come from a single mass stranding. While this study allowed us to reach some conclusions about the reproductive biology of female G. melas edwardii in the Southwestern Atlantic Ocean, further studies are needed to fully comprehend the behavior and biology of this species.

Effects of HACCP system implementation on reproduction, milk quality, and milk sanitation on dairy farms in Korea

The objective of this study was to investigate the influence of hazard analysis critical control point (HACCP) system implementation on the reproductive efficiency of dairy cattle, milk quality, and veterinary medicine use in dairy farms across Korea. Data were collected from 50 dairy farms before and after the implementation of the HACCP system. Importantly, somatic cell number and bacterial count in raw milk, and monthly expenses for medicine were lower after HACCP system implementation (p&lt;0.05). However, the breeding interval, use of different classes of antibiotics, milk protein, and milk fat content were not changed by implementing the HACCP system. These results indicated that implementation of the HACCP system on dairy farms may reduce the use of veterinary medicine and improve milk sanitation levels.

A deterministic, dynamic systems model of cow-calf production: The effects of breeding replacement heifers before mature cows over a 10-year horizon.

Some cattle production experts believe that cow-calf producers should breed replacement heifers (nulliparous cows) before cows (primiparous and multiparous cows), sometimes referred to as providing a heifer lead time (tHL). Our objective was to model the effects different durations of tHL may have on measures of herd productivity, including the percent of the herd cycling before the end of the first 21 d of the breeding season (%C21), the percent of the herd pregnant at pregnancy diagnosis (%PPD), the distribution of pregnancy by 21-d breeding intervals, the kilograms of calf weaned per cow exposed (KPC), and the replacement percentage (%RH), using a deterministic, dynamic systems model of cow-calf production over a 10-yr horizon. We also wished to examine differences in the effect of tHL related to the primiparous duration of postpartum anestrus (dPPA). The study model examined 6 different dPPA for primiparous cows (60, 70, 80, 90, 100, or 110 d). The multiparous cow duration of postpartum anestrus was set to 60 d. The breeding season length for nulliparous cows was 63 d, as was the breeding season length for primiparous and multiparous cows. Nulliparous cows were modeled with a tHL of 0, 7, 14, 21, 28, 35, or 42 d. Results are reported for the final breeding season of the 10-yr horizon. Increasing tHL resulted in a greater %C21 for the herd and for primiparous cows. Length of tHL had minimal impact on the %PPD unless the dPPA was 80 d or greater. For a dPPA of 110 d, a 0 d tHL resulted in the herd having 88.1 %PPD. When tHL was 21 d, the %PPD increased to 93.0%. The KPC was 161.2 kg when the dPPA was 110 d and tHL was 0 d and improved to 183.2 kg when tHL was increased to 42 d. The %RH did not vary much unless the dPPA was 90 d or greater, but increasing tHL resulted in decreased %RH. Based on the model results, increasing tHL improves the production outcomes included in the analysis, but herds with dPPA of 90 d or greater had the greatest degree of improvement. For these herds, approximately two-thirds of the improvement in outcomes by increasing tHL from 0 d to 42 d was realized when tHL was 21 d. Costs are likely incurred when implementing tHL in a breeding management program, and an ideal tHL likely depends on the dPPA of the herd, the expected improvement in productivity, and the costs associated with increasing tHL. Determining the dPPA of a herd could help veterinarians and producers develop optimal herd management strategies.

A deterministic, dynamic systems model of cow-calf production: The effects of the duration of postpartum anestrus on production parameters over a 10-year horizon

The duration of postpartum anestrus (dPPA) is important to consider for reproductive performance and efficiency in cow-calf operations. We developed a deterministic, dynamic systems model of cow-calf production over a 10-yr horizon to model the effects that dPPA had on measures of herd productivity, including the percentage of cows cycling before the end of the first 21 d of the breeding season (%C21), the percentage of cows pregnant at pregnancy diagnosis (%PPD), the distribution of pregnancy by 21-d breeding intervals, the kilograms of calf weaned (KW), the kilograms of calf weaned per cow exposed (KPC), and the replacement percentage. A 1,000-animal herd was modeled, with the beginning and ending dates for a 63-d natural service breeding season being the same for eligible replacement heifers (nulliparous cows) and cows (primiparous and multiparous cows). Herds were simulated to have a multiparous cow dPPA of 50, 60, 70, or 80 d, with the dPPA for primiparous cows being set to 50, 60, 70, 80, 90, 100, or 110 d. Only combinations where the primiparous dPPA was greater than or equal to the multiparous dPPA were included, resulting in 22 model herds being simulated in the analysis. All other model parameters were held constant between simulations. In model season 10, the %C21 was 96.2% when the multiparous cow and primiparous cow dPPA was 50 d and was 48.3% when the multiparous cow and primiparous cow dPPA was 80 d. The %PPD in model season 10 for these same herds was 95.1% and 86.0%, respectively. The percentage of the herd becoming pregnant in the first 21 d of the breeding season also differed between these herds (61.8% and 31.3%, respectively). The 10-yr total KW was more than 275,000 kg greater for the herd with a 50-d multiparous cow and primiparous cow dPPA when compared with the herd with the 80-d multiparous and primiparous cow dPPA and had a model season 10 KPC of 180.8 kg compared with 151.4 kg for the longer dPPA. The model results show that both the multiparous cow and primiparous cow dPPA affect herd productivity outcomes and that a dPPA less than 60 d results in improved production outcomes relative to longer dPPA. Veterinarians and producers should consider determining the dPPA to aid in making management decisions to improve reproductive performance of cow-calf herds.

Preliminary Remarks in Hormonal Treatments Effects on Reproduction Period in Cows

The early resumption of estrous cycles following calving is important for high reproductive efficiency and for the cows which haven’t been observed in estrus during the first 60 days after calving have a significantly higher risk of being culled than cows that have displayed estrus (Opsomer et al., 2000). The aim of this study was to determine the effect of hormonal treatment on reproduction period in cows, but also to establish if there is any significant difference in some reproductive parameters between cows treated with hormonal medication and cows which resumed ovarian cyclicity before 60 days postpartum. This study was performed in a dairy cows farm in North-Eastern Moldavia, over a period of 2 consecutive years, on Romanian Black Spotted cows in order to determine hormonal treatments influence on reproduction period. Hormonal treatments used for the above mentioned diseases were represented by luteolytic agent prostaglandin F2I±, one of its potent analogues (Proliz, Biotur, Romania) and by administration of exogenous gonadotrophin releasing hormone (Receptal, Intervet, Romania). We noticed that average reproduction period (52.1 days) and the other breeding intervals that were taken under study (over a two years period), presented different values for cows that have been under hormonal medication treatment, compared to those that resumed ovarian cyclicity before 60 days postpartum (52.7 days). Thus, this preliminary study supports the development of a more detailed study on several dairy cows farms in order to investigate the answer of different types of hormonal treatments against persistent corpus luteum and cystic ovarian disease.

Tough decisions: Reproductive timing and output vary with individuals' physiology, behavior and past success in a social opportunistic breeder

This article is part of a Special Issue "SBN 2014".Photoperiod and the hormonal response it triggers are key determinants of reproductive timing in birds. However, other cues and physiological traits may permit flexibility in the timing of breeding and perhaps facilitate adaptation to global change. Opportunistic breeders are excellent models to study the adaptive significance of this flexibility, especially at the individual level. Here, we sought to quantify whether particular male physiological and behavioral traits were linked to reproductive timing and output in wild-derived zebra finches. We repeatedly assessed male stress-induced corticosterone levels (CORT), basal metabolic rate (BMR), and activity before releasing them into outdoor aviaries and quantifying each pair's breeding timing, investment, and output over a seven-month period. Despite unlimited access to food and water, the colony breeding activity occurred in waves, probably due to interpair social stimulations. Pairs adjusted their inter-clutch interval and clutch size to social and temperature cues, respectively, but only after successful breeding attempts, suggesting a facultative response to external cues. When these effects were controlled for statistically or experimentally, breeding intervals were repeatable within individuals across reproductive attempts. In addition, males' first laying date and total offspring production varied with complex interactions between pre-breeding CORT, BMR and activity levels. These results suggest that no one trait is under selection but that, instead, correlational selection acts on hormone levels, metabolism, and behavior. Together our results suggest that studying inter-individual variation in breeding strategy and their multiple physiological and behavioral underpinnings may greatly improve our understanding of the mechanisms underlying the evolution of breeding decisions.

The Sub-Annual Breeding Cycle of a Tropical Seabird

Breeding periodicity allows organisms to synchronise breeding attempts with the most favourable ecological conditions under which to raise offspring. For most animal species, ecological conditions vary seasonally and usually impose an annual breeding schedule on their populations; sub-annual breeding schedules will be rare. We use a 16-year dataset of breeding attempts by a tropical seabird, the sooty tern (Onychoprion fuscatus), on Ascension Island to provide new insights about this classical example of a population of sub-annually breeding birds that was first documented in studies 60 years previously on the same island. We confirm that the breeding interval of this population has remained consistently sub-annual. By ringing >17000 birds and re-capturing a large sample of them at equivalent breeding stages in subsequent seasons, we reveal for the first time that many individual birds also consistently breed sub-annually (i.e. that sub-annual breeding is an individual as well as a population breeding strategy). Ascension Island sooty terns appear to reduce their courtship phase markedly compared with conspecifics breeding elsewhere. Our results provide rare insights into the ecological and physiological drivers of breeding periodicity, indicating that reduction of the annual cycle to just two life-history stages, breeding and moult, is a viable life-history strategy and that moult may determine the minimum time between breeding attempts.

Observation of intra‐group and extra‐group copulation and reproductive characters in free ranging groups of western black crested gibbon (Nomascus concolor jingdongensis)

Black crested gibbons (Nomascus concolor) are 1 of only 3 gibbon species that have been observed in long-term polygynous groups, but their mating behavior and reproductive characters have never been reported. Based on population monitoring over 7 years and direct observation for 26 months of the study groups in Wuliang Mountain, central Yunnan, we describe for the first time the copulation behavior and breeding pattern of free-ranging western black crested gibbons. The gestation period of black crested gibbons is estimated to be between 6 and 7 months. The average breeding interval is 3.5 years, with infant independence at approximately 2.5 years. We observed 2 intra-group copulations and 5 extra-group copulations. Copulations were initiated when a female gave a 'solicitation' gesture. When a male made any mating attempt, the female might refuse it. These results demonstrate direct female mate choice. Both male and female gibbons dispersed from their natal groups and sometimes replaced paired adults in other groups. We observed no evidence of infanticide during inter-group conflicts or after replacement of adults. Together with extra-group copulations, these phenomena indicate a flexible social organization and complex mating system. We also observed a male-biased sex ratio among offspring. More genetic work is necessary to describe the effects of inter-group copulation and the genetic diversity of this population.

Examination of multi-perturbation methods for ensemble prediction of the MJO during boreal summer

The impact of initialization and perturbation methods on the ensemble prediction of the boreal summer intraseasonal oscillation was investigated using 20-year hindcast predictions of a coupled general circulation model. The three perturbation methods used in the present study are the lagged-averaged forecast (LAF) method, the breeding method, and the empirical singular vector (ESV) method. Hindcast experiments were performed with a prediction interval of 10 days for extended boreal summer (May–October) seasons over a 20 year period. The empirical orthogonal function (EOF) eigenvectors of the initial perturbations depend on the individual perturbation method used. The leading EOF eigenvectors of the LAF perturbations exhibit large variances in the extratropics. Bred vectors with a breeding interval of 3 days represent the local unstable mode moving northward and eastward over the Indian and western Pacific region, and the leading EOF modes of the ESV perturbations represent planetary-scale eastward moving perturbations over the tropics. By combining the three perturbation methods, a multi-perturbation (MP) ensemble prediction system for the intraseasonal time scale was constructed, and the effectiveness of the MP prediction system for the Madden and Julian oscillation (MJO) prediction was examined in the present study. The MJO prediction skills of the individual perturbation methods are all similar; however, the MP‐based prediction has a higher level of correlation skill for predicting the real-time multivariate MJO indices compared to those of the other individual perturbation methods. The predictability of the intraseasonal oscillation is sensitive to the MJO amplitude and to the location of the dominant convective anomaly in the initial state. The improvement in the skill of the MP prediction system is more effective during periods of weak MJO activity.