Successive Breeding Seasons Research Articles

Food supplementing peregrine falcon (Falco peregrinus tundrius) nests increase reproductive success with no change in mean parental provisioning rate.

Parents are expected to exhibit intermediate levels of investment in parental care that reflect the trade-off between current versus future reproduction. Providing parents with supplemental food may allow for increased care to the current brood (additive model), re-allocation of parental effort to other behaviours such as self-maintenance (substitution model), or may provide parents with a buffer against provisioning shortfalls (insurance model). We investigated the impact of parental food supplementation on provisioning behaviour and breeding success in Arctic-breeding peregrine falcons (Falco peregrinus tundrius) over five successive breeding seasons (2013-2017). We found that supplemental feeding had no impact on mean provisioning rates, yet resulted in increased nestling survival probability, increased nestling body mass and decreased variance in nestling body mass and provisioning rates. These results are consistent with parents adopting a hybrid of the additive and substitution models. We suggest that food supplementation enables increased investment in other forms of parental care (e.g. nest defence, brooding) without altering mean provisioning rates. The lack of observed effects on mean provisioning rates, coupled with increased survival and body mass of offspring, suggests a potential reallocation of parental effort. The findings contribute to understanding the responses of peregrine falcons to food supplementation, highlighting the need for future studies to explore broader environmental contexts and potential long-term effects on parental survival and future reproduction.

Nesting habitat of the Brown-throated Martin Riparia paludicola mauritanica in Morocco

The Brown-throated Martin Riparia paludicola (subspecies mauritanica) of family Hirundinidae is endemic to Morocco and known for its ability to dig tunnels in earthen banks in which it nests. The nature of the sediment and the morphological features of the nest holes and riverbank habitat have not been thoroughly described across the species’ range in Morocco. Here, we present a qualitative and quantitative analysis of the textural characteristics of the sediment chosen by the martins in two successive breeding seasons, using a sample of 104 nests, which covered most of the species’ distribution range in Morocco. We also studied the surrounding landscape and morphological features of a total of 114 nests. Our observations show that besides nesting in natural riverbank habitat, the Brown-throated Martin can use both manmade embankments and substrates (even cement and concrete) to carry out a successful breeding cycle. This study provides important information on the nesting habitat of the Brown-throated Martin across Morocco. We believe that such descriptive work can help with the conservation of this Moroccan endemic by better targeting the right habitat to either protect or restore. The findings also include information useful to assist in creating new nesting sites for the species.

Embryo recovery on consecutive days from Day 6.5 to obtain small embryos for vitrification: Is it effective?

To successfully vitrify equine embryos without aspiration or puncture of the blastocoele cavity, current methodology requires embryos ≤300µm. Such embryos are obtained by flushing mares shortly after the presumed time of entry of the embryo into the uterus (6–6.5 days post ovulation). Ovulation, and hence the timing of the flush, is usually calculated from expected ovulation times following administration of an induction agent. However, recovery rates tend to be lower at 6.5 days. A precise time for ovulation helps, but its determination is management intensive, and entry into the uterus varies by a reported 12h. The aim of this study was to determine if flushing donor mares on successive days after they failed to give an embryo on Day 6.5-7 increased recovery rates of embryos ≤300µm. During successive breeding seasons 442 inseminated cycles from donor mares, aged 3-21 years, were flushed for embryos on Day 6.5-7 with the aim of obtaining embryos ≤300µm for vitrification. Mares were flushed with Ringer's Lactate in a closed system and oxytocin given before the third flush. Filter contents were placed in a Petri dish prior to rinsing the filter with 10% PVA in Ringer's Lactate. If no embryo was found flunixin meglumine was administered and the mare re-flushed 24h later. From 442 first flushes 151 (34.2%) were positiveand 168 embryos were recovered with a median diameter of 170 µm (range; 140-320µm). The 292 negative mares, and 3 double-ovulating mares that yielded only one embryo at the first flush, were re-flushed the following day with 49 (16.6%) positive flushes yielding 51 embryos (180µm; 150-400µm). A subset of the negative mares from the second recovery attempt (n=35) were flushed the following day and 7 (20.6%) gave embryos with a median diameter of 170µm (range; 150-200 µm). Combining all flushing days, 226 embryos were recovered of which only 4 (1.8%) were ≥300µm. Although approaching significance, no difference existed in the size of embryos recovered at the first, second or third flush (P=0.051). Mare age did not appear to be a factor on the likelihood of embryo recovery on the first, second or third attempt (12 vs. 14 vs. 12 y.o., respectively; P=0.130). Therefore, when flushing donor mares to recover embryos ≤300µm, re-flushing negative mares on consecutive days results in recovery of embryos suitable for vitrification without the need for blastocoele collapse. From a physiological aspect and allowing for the lack of a precise time for ovulation in the study, there appears to be a wider margin than Day 6–6.5 for entry of the embryo into the uterus.

Outcomes from an anti-gonadotropin-releasing hormone immunotherapeutic trial in large flying foxes (Pteropus vampyrus)

The anti-GnRH immunotherapeutic product Improvest was administered to intact male large flying foxes (Pteropus vampyrus) under managed care for androgen mitigation, leading to a decrease in agonistic behaviors, falls, and injuries from conspecific attention. 12 males were included in this study. Eleven bats received subcutaneous (SC) Improvest interscapular, and 1 animal received Improvest SC in its leg. Assessments included clinical presentation, treatment, behavior, and urine and fecal glucocorticoid metabolites and testosterone (T5) concentrations. Eleven of the 12 bats developed reactions, which included facial edema, localized irritation, swelling of the head and neck, and pruritus with varying degrees of skin ulceration and subsequent necrosis. Three of the animals required extensive treatments, and the 1 animal who received the injection in its leg was unaffected. Posttreatment, fecal glucocorticoid metabolite and/or T5 values were at or below the nonbreeding season baseline for 3 successive breeding seasons, and there was a reduction in agonistic interactions, falls, and injuries. A behavioral characteristic of this species is to focus on areas of irritation that exacerbated the extent of the skin wounds. Some cases required medical, surgical, and behavioral intervention. Large flying foxes may be particularly sensitive to this immunotherapeutic when given subcutaneously in the interscapular region. Despite this reaction, the positive long-term effects on behavior and multiyear reduction of hormones suggest that the use of this immunotherapeutic warrants further investigation, although the results should be taken into consideration with other factors such as handling, treatments, chronicity of lesions.

Does anthropization affect physiology, behaviour and life‐history traits of Montagu's harrier chicks?

AbstractThe last century has seen a steep decline in biodiversity, and anthropization is considered one of the major drivers of this decline. Anthropogenic disturbances, due to human presence and/or activities, may be perceived as chronic stressors by wildlife and potentially lead to deleterious effects on traits related to fitness. The main objective of the present study was to highlight the effects of these anthropogenic elements on wild birds on sparsely urbanized farmland, far less studied than in urbanized areas. We investigated during four successive breeding seasons whether the anthropization level, assessed by infrastructure density around nests, and the harvesting conditions around nests may impact physiological, behavioural and life‐history traits of Montagu's harrierCircus pygarguschicks. Higher anthropization levels were associated with higher basal corticosterone levels in nestlings during only one breeding season and a lower body condition at fledging for females, probably because they suffered from higher starvation than males. Nestlings reared in more anthropized areas or in harvested crops before their fledging harboured more fault bars on rectrices than those reared in less anthropized areas or in unharvested crops regardless of year and sex, which is suggestive of higher stress during development. Nestling behaviours were also impacted by anthropization level and harvesting conditions: chicks in harvested crops were more aggressive and in areas with higher anthropization levels more prone to escape than others. Because Montagu's harrier is a protected species, the impacts highlighted in the present study are a matter of concern, especially regarding farmland landscape modifications, and we advise limiting perturbations in areas where Montagu's harriers usually nest.

Soft coral reproductive phenology along a depth gradient: Can "going deeper" provide a viable refuge?

Many species across a wide range of taxa and habitats display phenological shifts and differences in response to both environmental gradients and climate change. Moreover, the wide‐scale decline of numerous ecosystems is leading to increasing efforts to identify zones that might serve as natural refuges from various disturbances, including ocean warming. One such refuge was suggested to be that of the deep coral reefs, but whether depth can provide coral populations with a viable and reproductive refuge remains unclear. Given the global coral‐reef degradation and the key role that corals play as ecosystem engineers, their reproductive ecology has been widely studied. A particular knowledge gap nonetheless exists regarding coral reproductive phenology along a depth gradient. Filling in this gap may uncover the environmental cues that regulate coral reproduction, leading to better predictions of population connectivity, and their possible responses to climate change and other environmental changes. Here, using long‐term in situ observations of the soft coral Rhytisma fulvum's reproductive activity along its entire depth range (0–45 m), we examined the relationship among several environmental factors and the coral's reproductive phenology and activity over five successive annual breeding seasons. Compared with the shallow depths, a lower number of reproducing colonies was found in habitats deeper than 30 m, highlighting possible constraints on coral reproduction at the deeper end of their range. Our results further revealed that an increase in seawater temperature over 1–2‐day intervals during the breeding season correlated with the onset of reproductive activity along the depth gradient, leading to different reproductive periodicities in different depths. These differences suggest that differential temperature regimes and reproductive timing across depth may create intraspecific temporal reproductive segregation, possibly reducing connectivity among populations along a depth gradient. Moreover, we found high variability among years in both the timing of breeding activities and in the level of reproductive synchrony among corals from different depths. Overall, our study questions whether depth can provide a long‐term and viable refuge for corals in the face of global environmental changes.

Developing artificial nest boxes for a large aquatic mammal

Abstract Nest boxes and other human‐made constructions have been widely and successfully used as conservation tools to increase nest‐availability for hollow‐dependent fauna, especially birds and some small and medium mammals. This study applies, for the first time, this recovery technique to a large aquatic mammal, aiming to improve resting, birthing and nursing sites of endangered Saimaa ringed seals (Pusa hispida saimensis) by developing artificial nest boxes. This landlocked subspecies' breeding habitat is severely affected by climate change. Because of mild winters, sufficient ice and snow habitat for subnivean lairs is lacking. In this study, floating nest boxes were developed. It was found that free‐ranging ringed seals accept nest boxes as sites for resting, birthing and nursing. Thirty‐four boxes in total were offered during six successive breeding seasons. Almost half (47%) of the available boxes were used by seals, and two pups were born and reared in the boxes during the 6‐year study. Our study indicates that this innovative technique can be a valuable tool for the Saimaa ringed seal conservation in the changing climate.

Perineuronal nets in HVC and plasticity in male canary song.

Songbirds learn their vocalizations during developmental sensitive periods of song memorization and sensorimotor learning. Some seasonal songbirds, called open-ended learners, recapitulate transitions from sensorimotor learning and song crystallization on a seasonal basis during adulthood. In adult male canaries, sensorimotor learning occurs each year in autumn and leads to modifications of the syllable repertoire during successive breeding seasons. We previously showed that perineuronal nets (PNN) expression in song control nuclei decreases during this sensorimotor learning period. Here we explored the causal link between PNN expression in adult canaries and song modification by enzymatically degrading PNN in HVC, a key song control system nucleus. Three independent experiments identified limited effects of the PNN degradation in HVC on the song structure of male canaries. They clearly establish that presence of PNN in HVC is not required to maintain general features of crystallized song. Some suggestion was collected that PNN are implicated in the stability of song repertoires but this evidence is too preliminary to draw firm conclusions and additional investigations should consider producing PNN degradations at specified time points of the seasonal cycle. It also remains possible that once song has been crystallized at the beginning of the first breeding season, PNN no longer play a key role in determining song structure; this could be tested by treatments with chondroitinase ABC at key steps in ontogeny. It would in this context be important to develop multiple stereotaxic procedures allowing the simultaneous bilateral degradation of PNN in several song control nuclei for extended periods.

Seasonal and diel activity patterns of the endangered taiga bean goose (Anser fabalis fabalis) during the breeding season, monitored with camera traps.

Taiga bean goose (Anser fabalis fabalis) is an endangered subspecies that breeds sporadically in remote habitats in the arctic and boreal zones. Due to its elusive behaviour, there is a paucity of knowledge on the behaviour of taiga bean goose during the breeding season, and survey methods for monitoring numbers in the breeding areas are lacking. Camera traps are a useful tool for wildlife monitoring, particularly when there is a need for non-invasive methods due to the shy nature of the species. In this study, we tested the use of camera traps to investigate seasonal and diel activity patterns of taiga bean goose in Finland over two successive breeding seasons, 2018 and 2019. We did this by modelling counts of geese from images with generalized linear and additive mixed models. The camera type (cameras placed by experts specialized in bean goose ecology vs randomly placed cameras) did not influence the count of taiga bean goose (p = 0.386). However, the activity varied significantly by region, Julian day, time of day and temperature, with the study site (individual peatland) and year adding substantial random variation and uncertainty in the counts. Altogether, the best fitting model explained nearly 70% of the variation in taiga bean goose activity. The peak in activity occurred about a month later in the southernmost region compared to the more northern regions, which may indicate behaviours related to migration rather than breeding and moulting. Our results show that long-term monitoring with game camera traps provide a potential unobtrusive approach for studying the behavioural patterns of taiga bean goose and can increase our ecological knowledge of this little-known subspecies. The results can be applied to planning of the annual censuses and finding the optimal time frame for their execution.

Nest site selection and breeding ecology of the Ferruginous Duck (Aythya nyroca) in Algeria

Ecologically, the Nature Reserve of Tonga Lake (northeastern Algeria) is very important for waterbirds. This study investigates breeding biology of an emblematic species of this region: The Ferruginous Duck (Aythya nyroca), a duck ranked globally 'Near Threatened' on the IUCN Red List. This study aimed to determine wetland environmental variables influencing nest site selection and breeding success of the species. Over two successive breeding seasons (2016 and 2017), the effects of habitat characteristics and nest traits on breeding parameters of 50 nests constructed on alder carr of the lake and offshore floating vegetation islets in the center of the waterbody were analyzed using generalized linear models (GLM). Clutch size averaged 9.8 ± 0.7 eggs (range: 2–26 eggs) with 66% hatching success. Desertion of the nest (i.e. nest abandonment by the parents during the period of egg-laying and/or incubation) was the main cause for breeding failure (18% of total nests). Clutch size was positively related to nest surface and nest depth, but it decreased with the increase in the distance of nest on the vegetation platform to water. GLM revealed that breeding success was positively associated with late clutches; with a negative effect of conspecific nest density on clutch size and breeding success. Nest-site choice is resulted from interspecific competition and/or is affected by the reduced number of favorable nesting sites. Nine nests (18%) were parasitized by the same species of which 67% were central nests. Only 2% of the nests studied were parasitized by Oxyura leucocephala nesting at the site. Possible explanations of nest site selection of Aythya nyroca in the study area are discussed. Variations in selection pressures may explain the relationships between the choice and characteristics of nest site in the Ferruginous duck at Lake Tonga.

Technological approaches to the problem of double ovulation and twin pregnancies in mares

The aim of the work was to determine and justify the correct technological approach in cases of double ovulation and twin pregnancies in mares. The frequency of single and double ovulations (n=2207), the level of twin pregnancies and the results of manual reduction of excess embryo in mares were studied. The average level of double ovulations was 9.5 % per year, and it had no significant difference in mares of different breeds (Russian Trotter, French Trotter, Standardbred and others). The number of poliovulations in February-March (3.2–4.9 %) and August (5.1 %) was significantly (p <0.05) lower than it was in April-July (9.9–11.3 %). The number of multiple ovulations gradually decreased from young (4–8 yo) to old (>14 yo) mares (11.9 – 5.1 %) (p <0.05). The third part of all mares (35.8 %) with poliovulations repeated it during one season, and after 1–3 successive breeding seasons. The mating of mares with double ovulation resulted in 35.0 % of twin embryos and 28.1 % of single embryos. The success rate of manual reduction of the second embryo on days 12–14 was 85.3 %.

Pair bonding in Eurasian Bullfinches Pyrrhula pyrrhula: observations from a colour-ringing study

ABSTRACT A colour-ringing project was used to study pair-bond formation by Eurasian Bullfinches Pyrrhula pyrrhula visiting a garden in northern England. During the period July 2011 to April 2017, 427 Bullfinches were colour ringed, and 235 (55%) resighted at a seed feeder. Thirty-six pairs were identified with both partners carrying a colour ring. There was evidence that some couples might initiate pair-bond formation from as early as November, but most new bonds were first identified from January onwards. The earliest bonds were formed between birds over one year old, and older females appeared to preferentially select older males. Nearly all partnerships continued until the disappearance of one or both birds, consistent with death or dispersal, and for 12 pairs where one bird disappeared the other was subsequently observed to form a new partnership. For two longer-surviving pairs the bond was maintained over two successive breeding seasons (23 and 27 months) and, for another, from winter to winter (13 months). The findings support the previous supposition that the typical breeding strategy for this species is one of bond fidelity until the death of one or both partners, and the subsequent formation of a new bond by the surviving partner. However, there was evidence that three couples had separated and survived to form new partnerships, with the female separating in one case from a bigamous male. The study provides novel information about the pair-bond system of this species.

Reactive stress-coping styles show more variable reproductive expenditure and fitness outcomes

Stress-coping styles dictate how individuals react to stimuli and can be measured by the integrative physiological parameter of resting heart-rate variability (HRV); low resting HRV indicating proactive coping styles, while high resting HRV typifies reactive individuals. Over 5 successive breeding seasons we measured resting HRV of 57 lactating grey seals. Mothers showed consistent individual differences in resting HRV across years. We asked whether proactive and reactive mothers differed in their patterns of maternal expenditure and short-term fitness outcomes within seasons, using maternal daily mass loss rate to indicate expenditure, and pup daily mass gain to indicate within season fitness outcomes. We found no difference in average rates of maternal daily mass loss or pup daily mass gain between proactive and reactive mothers. However, reactive mothers deviated more from the sample mean for maternal daily mass and pup daily mass gain than proactive mothers. Thus, while proactive mothers exhibit average expenditure strategies with average outcomes, expenditure varies much more among reactive mothers with more variable outcomes. Overall, however, mean fitness was equal across coping styles, providing a mechanism for maintaining coping style diversity within populations. Variability in reactive mothers’ expenditures and success is likely a product of their attempts to match phenotype to prevailing environmental conditions, achieved with varying degrees of success.

Impact of Annual Bacterial Epizootics on Albatross Population on a Remote Island

The reduced species richness typical of oceanic islands provides an interesting environmental setup to examine in natura the epidemiological dynamics of infectious agents with potential implications for public health and/or conservation. On Amsterdam Island (Indian Ocean), recurrent die-offs of Indian yellow-nosed albatross (Thalassarche carteri) nestlings have been attributed to avian cholera, caused by the bacterium Pasteurella multocida. In order to help implementing efficient measures for the control of this disease, it is critical to better understand the local epidemiology of P. multocida and to examine its inter- and intra-annual infection dynamics. We evaluated the infection status of 264 yellow-nosed albatrosses over four successive breeding seasons using a real-time PCR targeting P. multocida DNA from cloacal swabs. Infection prevalence patterns revealed an intense circulation of P. multocida throughout the survey, with a steady but variable increase in infection prevalence within each breeding season. These epizootics were associated with massive nestling dies-offs, inducing very low fledging successes (≤ 20%). These results suggest important variations in the transmission dynamics of this pathogen. These findings and the developed PCR protocol have direct applications to guide future research and refine conservation plans aiming at controlling the disease.

Reproductive Performance, Mate Fidelity and Nest Cavity Fidelity in Red-Billed Tropicbirds Phaethon aethereus mesonauta on St. Eustatius, Caribbean Netherlands

Mate choice and nest cavity selection are directly linked to reproductive performance in seabirds, and disruption of these can result in breeding failure. The Red-billed Tropicbird Phaethon aethereus mesonauta breeds on inaccessible and remote islands, nesting primarily in natural rock cavities. I examined the relationship between reproductive performance and mate and nest cavity fidelity on St. Eustatius from 2012 to 2016, corresponding to four successive breeding seasons. The majority of nest failures occurred during the incubation stage. Pairs that failed in their first breeding attempt and laid a replacement clutch were more likely to be faithful to their mate and nest cavity within and between seasons than pairs that bred successfully. Only two replacement clutches (3.8%) were laid after the loss of a chick in the first breeding attempt, whereas the remaining 50 replacement clutches (96.2%) were laid after the loss of an egg. The stage at which pairs split had no influence on mate or nest cavity retention the following season. There were no significant differences in the weight or morphological measurements of chicks from pairs that retained their nest mate and/or cavity and those that switched. The results of this study suggest that switching nest mate or nest cavity does not necessarily improve subsequent breeding success among Red-billed Tropicbirds on St. Eustatius.

Seasonal changes of perineuronal nets and song learning in adult canaries (Serinus canaria)

Songbirds learn their song during a sensitive period of development associated with enhanced neural plasticity. In addition, in open-ended learners such as canaries, a sensitive period for sensorimotor vocal learning reopens each year in the fall and leads to song modifications between successive breeding seasons. The variability observed in song production across seasons in adult canaries correlates with seasonal fluctuations of testosterone concentrations and with morphological changes in nuclei of the song control system (SCS). The sensitive periods for song learning during ontogeny and then again in adulthood could be controlled by the development of perineuronal nets (PNN) around parvalbumin-expressing interneurones (PV) which limits learning-induced neuroplasticity. However, this relationship has never been investigated in the context of adult vocal learning in adult songbirds. Here we explored PNN and PV expression in the SCS of adult male Fife Fancy canaries in relation to the seasonal variations of their singing behaviour. We found a clear pattern of seasonal variation in testosterone concentrations and song production. Furthermore, PNN expression was significantly higher in two specific song control nuclei, the robust nucleus of the arcopallium (RA) and the Area X of the basal ganglia, during the breeding season and during the later stages of sensorimotor song development compared to birds in an earlier stage of sensorimotor development during the fall. These data provide the first evidence that changes in PNN expression could represent a mechanism regulating the closing-reopening of sensitive periods for vocal learning across seasons in adult songbirds.

Vocal instability over time in individual male European nightjars, Caprimulgus europaeus: recommendations for acoustic monitoring and surveys

ABSTRACTAcoustic monitoring of birds is developing rapidly as equipment, methods and analyses improve. However, most population monitoring studies still utilise traditional techniques like mark-recapture or line transects. Previous researchers used vocal recordings of male European nightjars, Caprimulgus europaeus, to identify individuals, finding that four acoustic parameters correctly assigned 98.5% of calls to individuals. We tested their methods on a population of European nightjars recorded over two successive breeding seasons and found that percentage of males correctly classified within a season reached a maximum of 73.5%, rising to 75% if full-length calls and 13 acoustic parameters were used. We tested whether males could be re-identified over a two-year period and found that only 20% of calls were assigned to the same putative territorial individuals, despite separate ringing data showing that males can maintain site fidelity for up to eight years. Our results indicate that the characteristics of male nightjar vocalisations may alter over time. We therefore recommend that vocal discrimination be used in conjunction with existing monitoring techniques when surveying for population monitoring, that as many call parameters as possible are used and that recording for automated presence/absence surveys takes place over a short time-frame.

Nestling White-backed Vulture (&lt;i&gt;Gyps africanus&lt;/i&gt;) eaten by a Verreaux’s Eagle (&lt;i&gt;Aquila verreauxii&lt;/i&gt;) at a nest occupied for a record 21 years.

An adult Verreaux’s Eagle ( Aquila verreauxii ) was observed eating a White-backed Vulture ( Gyps africanus ) nestling at a nest at Sango in the Save Valley Conservancy, south-eastern Zimbabwe on 13 October 2017. This nest has been regularly occupied for 21 successive breeding seasons. To our knowledge, this observation represents a previously unrecorded species in the diet of Verreaux’s Eagle, and it is also apparently the longest known continually-occupied White-backed Vulture nest.

Relationship between anti-Müllerian hormone and fertility in the mare

The objectives of this study were to evaluate; 1) the stability of measured serum anti-Müllerian hormone (AMH) concentrations in samples after multiple freeze-thaw cycles, 2) the repeatability of AMH concentrations within mares during the same breeding season as well as across breeding seasons, and 3) the relationship between serum AMH concentrations and fertility (measured as first cycle pregnancy rates) in thoroughbred mares. For the first aim, AMH concentrations (n = 9) were examined across four freeze-thaw cycles with no significant change in measured AMH concentrations. For the second aim, serum AMH concentrations (n = 12) were examined over three successive estrous cycles and over two successive breeding seasons and AMH levels were significantly correlated for individual animals within (r; 0.71–82) or across breeding seasons (r = 0.81). For the third aim, Thoroughbred mares (n = 419) on farms in central Kentucky had blood samples taken during estrus. Pregnancy was determined with transrectal ultrasonography at Days 13–18 after mating and ovulation, and pregnancy outcome was recorded as open, pregnant or twins. The relationships between mare age, serum AMH concentrations and the interaction of age and AMH with pregnancy outcome was examined by nominal logistic regression, and the relationship between serum AMH concentrations and mare age, pregnancy outcome and the interaction of age and pregnancy outcome was examined by ANOVA. Data in this study were then stratified according to quartiles into lower (25%), mid-50% (second and third quartiles combined - 50%) and upper (25%) quartiles for age and serum AMH concentration for further analysis by logistic regression. There were significant effects of mare age and pregnancy outcome, but not their interaction on serum AMH concentrations which were higher (P = 0.04) in pregnant than in open mares (0.65 ± 0.03 vs 0.55 ± 0.04 ng/mL, respectively). Likewise, logistic regression revealed significant effect of mare age and AMH but not their interaction on pregnancy outcome on the first mated cycle. Mares in the lower AMH quartile were more likely to be open at Day 13–18 than mares in the middle (odds ratio (OR) = 1.87)=13 or upper quartile (OR = 2.62) for AMH concentrations. Mares in the mid-50% (OR = 3.91) or upper (OR = 4.97) age quartile were more likely to be open at Day 13–18 compared to mares in the young age quartile. Based upon a Chi-squared analysis, the proportion of pregnant mares differed across age quartiles (P < 0.0001) and was greater (P < 0.05) in the young mare quartile. The proportion of pregnant mares tended to differ across AMH quartile (P = 0.1), and when adjusted for age quartile using the Cochran-Mantel-Haenszel Test, the proportion of pregnant mares differed (P < 0.05) across AMH quartile. In conclusion, mares with peripheral AMH concentrations in the lowest quartile had lower fertility compared to mares in the mid-50% or upper quartile.

Foraging plasticity in seabirds: A non-invasive study of the diet of greater crested terns breeding in the Benguela region.

Marine predators, such as seabirds, are useful indicators of marine ecosystem functioning. In particular, seabird diet may reflect variability in food-web composition due to natural or human-induced environmental change. Diet monitoring programmes, which sample diet non-invasively, are valuable aids to conservation and management decision-making. We investigated the diet of an increasing population of greater crested terns Thalasseus bergii in the Western Cape, South Africa, during three successive breeding seasons (2013 to 2015), when populations of other seabirds feeding on small pelagic schooling fish in the region were decreasing. Breeding greater crested terns carry prey in their bills, so we used an intensive photo-sampling method to record their diet with little disturbance. We identified 24,607 prey items from at least 47 different families, with 34 new prey species recorded. Fish dominated the diet, constituting 94% of prey by number, followed by cephalopods (3%), crustaceans (2%) and insects (1%). The terns mainly targeted surface-schooling Clupeiformes, with anchovy Engraulis encrasicolus the most abundant prey in all three breeding seasons (65% overall). Prey composition differed significantly between breeding stages and years, with anchovy most abundant at the start of the breeding season, becoming less frequent as the season progressed. The proportion of anchovy in the diet also was influenced by environmental factors; anchovy occurred more frequently with increasing wind speeds and was scarce on foggy days, presumably because terns rely in part on social facilitation to locate anchovy schools. The application of this intensive and non-invasive photo-sampling method revealed an important degree of foraging plasticity for this seabird within a context of locally reduced food availability, suggesting that, unlike species that specialise on a few high-quality prey, opportunistic seabirds may be better able to cope with reductions in the abundance of their preferred prey.