The diet of a declining Red-billed Chough Pyrrhocorax pyrrhocorax population on Islay,Scotland

Capsule: We quantify Red-billed Chough Pyrrhocorax pyrrhocorax diet from faecal samples collected on Islay. Dung invertebrates formed the majority of prey biomass in dune pasture and Tipulid larvae in mixed pasture but Aphodius larvae were scarce in the diet, whereas they had been a major component in the 1980s. There are management implications from the indication of a reduction in availability of preferred food.     

Arthropods in diet of Little Bustards Tetrax tetrax during the breeding season in western France

Capsule Seasonal, age- and sex-related variations in the diet were studied during March to October.

Aims To determine which arthropod orders contributed most during the laying–rearing period and those important in determining breeding success of the species in an intensive agricultural habitat.

Methods Faeces (n = 388, 345 g) and three gut samples were dissected to determine which arthropod orders contributed most to the diet, especially during the laying–rearing period.

Results Coleoptera were the most numerous prey followed by Orthoptera, Dermaptera and Hymenoptera. No difference was observed in the diet of adult males and females. Although adults ate arthropods throughout the breeding season, plant material contributed 97–99% of faecal contents by weight in each month. Chicks, however, only ate arthropods, notably Coleoptera and Orthoptera, at least until 2–3 weeks old.

Conclusion Increasing arthropod availability would be a useful management tool for maintaining endangered Little Bustard populations by potentially increasing chick survival.     

A comprehensive demographic assessment of the endangered Fiordland crested penguin Eudyptes pachyrhynchus

ABSTRACT

Many species of Eudyptes penguin have shown substantial population declines and in response, there have been efforts to identify the key demographic parameters. Here, we present the demographic parameters of one of the least well known and the least abundant species of crested penguin, the endangered Fiordland crested penguin Eudyptes pachyrhynchus. A population study incorporating mark–recapture, nest occupancy and breeding success was conducted over 16 years at several sites in the northern half of the range of the species. Survival probabilities were calculated using standard Cormack–Jolly–Seber models and the Burnham Live and Dead model. The annual probability of true survival for banded birds and apparent survival for birds with transponders were both estimated at 89% during their adult years, which is similar to that reported for Eudyptes penguin species inhabiting more southerly latitudes. Annual juvenile survival was assessed for Fiordland crested penguins until their first return at 77%. The mean breeding success (0.61?±?0.02 chicks/pair) was higher than is observed for other crested penguin species, except the southern rockhopper penguin, which may be due to having lower A-egg ejection rates and higher rates of fledging two chicks per pair. Breeding success was related to the niche of predators present.     

The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet,survival, nest predation and moment of fledging

Capsule: The diet of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region was dominated by Viviparous Eelpout Zoarces viviparus. Risk of nest predation by avian and mammalian predators was perceived to be low, and hatching and fledging success were high.

Aims: To gain insight into the ecology of nestling Black Guillemots in the Baltic Sea region to fill knowledge gaps and benefit its conservation.

Methods: Two island groups in the Baltic Sea were visited several times during the breeding season of 2014 and 2015 to monitor nestling survival and fledging. In addition, camera traps were used in 2014 to monitor prey brought to chicks by adults and record possible nest predation events.

Results: Hatching success was 0.89 and 0.73 in 2014 and 2015, respectively, and fledging success was very high (0.95 and 0.97). No incidences of avian or mammalian predation were observed. Chicks fledged at night between 32 and 38 days after hatching. Viviparous Eelpout made up 95% of the prey items brought to the chicks by adults.

Conclusions: The hatching rate and fledging rate of the Black Guillemot was high in our study region. Juveniles seemed highly dependent on the availability of eelpout. Changes in the abundance of this species may therefore have negative effects on chick survival.     

Vocalizations and morphology: interpreting the divergence among populations of Chough Pyrrhocorax pyrrhocorax and Alpine Chough P. graculus

Capsule Differences in vocalizations among populations are mostly explained on morphological bases, but historical factors may have played a significant role in differentiation processes.

Aims To investigate the relationships among vocal and morphological variation in two corvids: Chough and Alpine Chough.

Methods We used data from 11 populations of Chough and seven populations of Alpine Chough spanning the Palearctic distribution of the two species. Three data sets (morphometry, spectrotemporal parameters of trill calls and acoustic repertoire) were analysed and their variation compared with uni- and multivariate techniques.

Results In both species, morphological differences among populations were correlated to spectro-temporal variation of trills; in particular, frequencies of calls were negatively correlated to wing length (an indicator of body size). By considering only co-existing populations of the two species, the magnitude of morphological and spectrotemporal divergence was similar.

Conclusions In both species, birds from populations with similar morphology uttered similar call types and trills with close spectrotemporal features. In particular, larger-sized populations, as expressed by wing length, emitted lower pitched calls. However, the fact that dissimilarities in repertoire and morphology were correlated cannot be explained only by appealing to functional explanations, as the observed intraspecific morphological variability does not seem to be high enough to promote consistent changes in the pool of calls. In this case, historical factors might have contributed to the present pattern of differentiation.     

Enhanced invertebrate prey production following estuarine restoration supports foraging for multiple species of juvenile salmonids (Oncorhynchus spp.)

Estuaries provide crucial foraging resources and nursery habitat for threatened populations of anadromous salmon. As such, there has been a global undertaking to restore habitat and tidal processes in modified estuaries. The foraging capacity of these ecosystems to support various species of out‐migrating juvenile salmon can be quantified by monitoring benthic, terrestrial, and pelagic invertebrate prey communities. Here, we present notable trends in the availability of invertebrate prey at several sites within a restoring large river delta in Puget Sound, Washington, U.S.A. Three years after the system was returned to tidal influence, we observed substantial additions to amphipod, copepod, and cumacean abundances in newly accessible marsh channels (from 0 to roughly 5,000–75,000 individuals/m²). In the restoration area, terrestrial invertebrate colonization was dependent upon vegetative cover, with dipteran and hymenopteran biomass increasing 3‐fold between 1 and 3 years post‐restoration. While the overall biodiversity within the restoration area was lower than in the reference marsh, estimated biomass was comparable to or greater than that found within the other study sites. This additional prey biomass likely provided foraging benefits for juvenile Chinook, chum, and coho salmon. Primary physical drivers differed for benthic, terrestrial, and pelagic invertebrates, and these invertebrate communities are expected to respond differentially depending on organic matter exchange and vegetative colonization. Restoring estuaries may take decades to meet certain success criteria, but our study demonstrates rapid enhancements in foraging resources understood to be used for estuary‐dependent wildlife.     

Buffering against food availability? The physical environment has little influence on breeding performance of fairy prions (Pachyptila turtur)

The breeding performance of seabirds is constrained by the availability of marine‐based prey, which may be influenced by competition with other seabirds, and environmental conditions. Fairy prion (Pachyptila turtur) populations have declined substantially in New Zealand since the introduction of mammalian predators; remaining small populations provide an opportunity to examine the effect of environmental factors on reproductive success in the absence of competition. Using 11 years of nest monitoring data and eight years of chick measurements we investigated (i) the link between physical environmental factors, breeding success rates and chick fledging size, and (ii) the relationship between chick fledging size and likelihood of natal‐colony recapture. Despite annual variations in the Southern Oscillation Index (SOI) and sea surface temperatures (SST), breeding success and chick fledging weights remained similar throughout the entire period, possibly due to the use of behavioural buffering mechanisms by parents. Fledgling wing lengths differed among years, and were predicted by early winter and early spring values of the SOI and late spring and summer SSTs. In years of high SOI and high SST, fairy prions fledged with longer wings, possibly due to increased availability of the euphausiid Nyctiphanes australis, their main prey. River flows and rainfall were unrelated to breeding success or chick measurements: the influence of freshwater on the marine system at this locality acts at smaller timescales than those studied here. Using the 2004 and 2005 cohorts, there was no link between fledging size and likelihood of recapture, except for the 2005 cohort which had unusually low 6‐year recapture rates, and shorter‐than‐average wing lengths. A combination of low sea temperatures and an El Niño event in 2005 may have led to a reduction in euphausiid availability, ultimately affecting post‐fledging survival.     

Effects of habitat fragmentation on provisioning rates, diet and breeding success in two species of tit (great tit and blue tit)

The aim of this study was to examine the effects of forest fragmentation on the ability of parent birds to provide their young with an adequate food supply. To examine whether prey population densities of the great tit (Parus major L.) and the blue tit (P. caeruleus L.) vary between study areas in different forest size classes we compared provisioning rates and chick diet and related these parameters to breeding success. We filmed 217 nests over two breeding seasons and collected data on frass fall as a general estimate of caterpillar availability. Nests which were attended by none or one parent only during filming (n = 46) were excluded from the analyses. In both years and for both species feeding rates were highest in the smallest fragments and lowest in the large forest. There was also a suggestion that differences in feeding rates between areas vary between years. We found no consistent tendency for prey size to change with forest size, although both species brought slightly smaller prey items to the nest in the smallest forest fragments and feeding rates correlated negatively with prey size. Caterpillars were the main item fed to nestlings, in both species. We found no evidence to suggest that either frass fall or the proportion of caterpillars in the diet varied with forest size. There was also no correlation between mean frass fall and the total number of caterpillars brought to the nests, in either species. Breeding success, as measured by clutch size, brood size, fledging weight and fledging success, did not differ between the small fragments and the large forest, in either species. There was also no relationship between provisioning rate (as concerns volume of prey fed to nestlings and the quality of chick diet) and breeding success parameters. In conclusion, this study does not suggest suboptimal foraging or breeding conditions in small fragments compared to a nearby large forest, for either species. Received: 23 June 1997 / Accepted: 29 December 1997     

Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

Impact of weather and climate variation on Hoopoe reproductive ecology and population growth

Preserving peripheral populations is a key conservation issue because of the adaptive potential to environmental change they provide for the species as a whole. Yet, peripheral populations are often small and isolated, i.e. more vulnerable to stochastic events and prone to extinction. We studied a peripheral population of Hoopoe (Upupa epops), a rare insectivorous farmland bird, in the Swiss Alps. We first investigated the effect of weather variation on food provisioning to chicks by Hoopoe parents. Second, while accounting for density-dependence, we tested the extent to which breeding success is governed by weather circumstances and assessed the possible consequences of climate variation on population growth. Provisioning rate and provisioned prey biomass were negatively affected by adverse weather (cool, rainy days), were higher in males and also increased with brood size. Much smaller proportions of molecrickets (Gryllotalpa gryllotalpa; the most profitable prey locally, constituting 93% of chicks’ food biomass) were provisioned on days with adverse weather, irrespective of brood size. Rainfall prior to hatching and during the first days of chick life had a negative impact on their survival, and there was a positive effect of temperature on chick survival just before fledging. Reproductive output was negatively affected by precipitation during the hatching period, but was enhanced by warm temperature just before hatching and in the last days before fledging. Our model showed that the variable reproductive output has a strong impact on the population growth: a succession of adverse, rainy springs would cause a rapid decline of the population. This case study confirms that conservation efforts may be obliterated if risks linked to increasing climate variability are not properly accounted for in the management of small peripheral populations.     

Reproductive measures and chick provisioning of Cory's Shearwater Calonectris diomedea borealis in the Azores

Capsule Timing of breeding influenced wing-length at fledging, and egg size may be an indicator of fledging weight and the amount of food received by chicks.

Aims To investigate chick growth, temporal patterns of chick food provisioning and the importance of indices of parental condition or quality, egg size and hatching date, to predict nestling body mass and wing-length at fledging, and compare breeding and chick feeding characteristics between colonies in the northeast Atlantic.

Methods A survey of Cory's Shearwater nests was carried out at Vila islet. A sample of 52 chicks, ringed and weighed at hatching, was selected to study chick growth and food provisioning.

Results Hatching success (51%) was much lower than fledging success (87%). Both hatching date and egg size contributed to explain wing-length at fledging, but hatching date, which was negatively correlated with wing-length at fledging, had the most important contribution (22%). There was some indication that egg size may explain variation in fledging weight and the amount of food received by chicks. Food delivery and feeding frequency of chicks varied throughout the chick development stage and three phases were distinguished: (1) 0–29 days, the highest feeding frequency values and a linear increase in food delivery; (2) 30–69 days, an oscillation in food delivery and medium feeding frequencies; (3) 70–90+ days, a sharp decrease in both food delivery and feeding frequency.

Conclusion Variation in food availability did not seem sufficient to override the overall importance of indices of parental quality in determining reproductive measures and chick provisioning. Breeding and feeding characteristics were similar between colonies in the northeast Atlantic, with variability in chick provisioning higher further south.     

Breeding biology and mating system of Brown Accentors Prunella fulvescens on the Tibet Plateau

ABSTRACT

Capsule: The mating system of the Brown Accentor Prunella fulvescens in the high altitudes of the Tibeta plateau is mainly monogamous but polyandry was recording in 9.7% of breeding groups.

Aims: To describe the poorly known breeding biology of Brown Accentors in the high-altitude environment of the northeastern Tibet plateau.

Methods: Individually colour-ringed birds were observed during two breeding seasons. Biometrics were recorded for breeders, and reproductive variables were quantified.

Results: Brown Accentors were territorial during the breeding season and were resident year-round. Most groups (90.3%, n?=?31 groups) were socially monogamous and the remainder (9.7%) were polyandrous, with two males sharing a female’s territory. Mean group size was 2.1 adults and the population adult sex ratio was 52% male. The birds raised a single brood during the breeding season. Nests were invariably located in Sea Buckthorn Hippophae rhamnoides. Eggs were laid between late June and late July, and mean clutch size was 3.4?±?0.6 (SD) eggs. Incubation was undertaken by the female and lasted 12.9?±?0.9 (SD) days. Both sexes provisioned young in the nest for 13.9?±?1.2 (SD) days. Females provided significantly more feeding visits than did males. Brood size at estimated fledging dates averaged 2.2?±?0.7 (SD) nestlings. Forty-five per cent of nesting attempts (n?=?37) fledged at least one nestling.

Conclusions: Like other species in the family Prunellidae, the Brown Accentor exhibits remarkable variation in its mating system.     

Environmental correlates of lake occupancy and chick survival of Black-throated Divers Gavia arctica in Scotland

Capsule Lake occupancy was related to the abundance of fish prey for adults (salmonids) and chick survival was related to type of diet, prey abundance and weather.

Aims To identify the factors determining lake occupancy and chick survival of Black-throated Divers breeding in Scotland.

Methods Measures of water chemistry, fish, invertebrates and physical characteristics were made for 90 lakes where occupancy had been monitored in at least five years between 1984 and 1995. Data on chick survival were available over this period for a smaller sample of lakes.

Results High occupancy rates were associated with a high abundance of small salmonids (the birds' principal prey) and complex shorelines. The mean number of chicks fledged per nest that hatched was 0.95 at lakes where Three-spined Sticklebacks Gasterosteus aculeatus and/or Minnows Phoxinus phoxinus were present; the mean number of chicks fledged was 0.64 where they were absent (and chicks are fed invertebrates). Chick survival on lakes with sticklebacks/Minnows was positively and significantly related to June temperature, and the abundance of these fish. At lakes lacking these small fish, chick survival was inversely related to sunshine duration in June. It is suggested that sunny weather in June can accelerate the emergence of aquatic insect larvae (especially Ephemeroptera) and lead to food shortage for small diver chicks.

Conclusions It is likely that there are sufficient suitable lakes to accommodate a moderate expansion of the Scottish Black-throated Diver population. An abundance of suitable fish prey, especially small-sized (<230 mm) salmonids, is of fundamental importance for diver conservation.     

Nest and foraging‐site selection in Yellowhammers Emberiza citrinella: implications for chick provisioning

Capsule Vegetation structure and invertebrate abundance interact to influence both foraging sites and nestling provisioning rate; when invertebrate availability is low, adults may take greater risks to provide food for their young.

Aims To investigate nesting and foraging ecology in a declining farmland bird whose fledging success is influenced by the availability of invertebrate prey suitable for feeding to offspring, and where perceived predation risk during foraging can be mediated by vegetation structure.

Methods Provisioning rates of adult Yellowhammers feeding nestlings were measured at nests on arable farmland. Foraging sites were compared with control sites of both the same and different microhabitats; provisioning rate was related to habitat features of foraging‐sites.

Results Foraging sites had low vegetation density, probably enhancing detection of predators, or high invertebrate abundance at high vegetation density. Parental provisioning rate decreased with increasing vegetation cover at foraging sites with high invertebrate abundance; conversely, where invertebrate abundance was low, provisioning rate increased with increasing vegetation cover.

Conclusions Vegetation structure at foraging sites suggests that a trade‐off between predator detection and prey availability influences foraging site selection in Yellowhammers. Associations between parental provisioning rate and vegetation variables suggest that where invertebrate abundance is high birds increase time spent scanning for predators at higher vegetation densities; however, when prey are scarce, adults may take more risks to provide food for their young.     

Breeding success and lutein availability in great tit (Parus major)

The relationship among temporal variation in the availability of carotenoid-rich food, tissue carotenoid levels and breeding success are poorly known. We studied how diet quality and quantity affect the carotenoid profile and fledging success of great tit (Parus major) nestlings along a pollution gradient. We found declining seasonal trend in lutein concentration of caterpillars, which may be the explanation for the declining trend in nestlings' lutein concentration of plasma with season, despite the increase in caterpillar biomass. This may be because the biomass of most lutein-rich caterpillars (autumnal moths) decreased and less lutein-rich caterpillars (sawflies) increased during the breeding season. The temporal difference in occurrence of different caterpillar species means that peak lutein availability does not coincide with peak caterpillar abundance. However the positive association between total larval biomass and the number of great tit fledglings may suggest that fledging success depends more on total caterpillar availability than on lutein concentration of caterpillars.     

Gauging resource exploitation by juvenile Chinook salmon (Oncorhynchus tshawytscha) in restoring estuarine habitat

In the context of delta restoration and its impact on salmonid rearing, success is best evaluated based on whether out‐migrating juvenile salmon can access and benefit from suitable estuarine habitat. Here, we integrated 3 years of post‐restoration monitoring data including habitat availability, invertebrate prey biomass, and juvenile Chinook salmon (Oncorhynchus tshawytscha) physiological condition to determine whether individuals profited from the addition of 364 ha of delta habitat in South Puget Sound, Washington, United States. Productivity in the restored mudflat was comparable to reference sites 3 years after dike removal, surpassing a mean total of 6 million kJ energy from invertebrate prey. This resulted from the development of a complex network of tidal channels and a resurgence in dipteran biomass that was unique to the restoration area. Consequently, a notable shift in invertebrate consumption occurred between 2010 and 2011, whereby individuals switched from eating primarily amphipods to dipteran flies; however, dietary similarity to the surrounding habitat did not change from year to year, suggesting that this shift was a result of a change in the surrounding prey communities. Growth rates did not differ between restored and reference sites, but catch weight was positively correlated with prey biomass, where greater prey productivity appeared to offset potential density‐dependent effects. These results demonstrate how the realized function of restoring estuarine habitat is functionally dependent. High prey productivity in areas with greater connectivity may support healthy juvenile salmon that are more likely to reach the critical size class for offshore survival.     

Niche dynamics of sympatric non-breeding shearwaters under varying prey availability

Variation in prey availability can cause changes in species interactions among marine predators. Foraging theory predicts that niche breadth will expand when resources become limited, possibly leading to higher niche overlap among sympatric species; however, a species’ niche can become constrained by interactions with other similar species, resulting in an inability to shift niche breadth or position. In coastal Newfoundland, Capelin Mallotus villosus is the main forage fish species and its availability (i.e. biomass) during the summer has varied considerably following a population collapse in the 1990s. During the summer, non-breeding Great and Sooty Shearwaters Ardenna gravis and A. grisea migrate and aggregate at annually persistent Capelin spawning sites. We used stable isotope ratios (δ¹³C, δ¹⁵N) of blood components (plasma, red blood cells) to investigate variation in isotopic niche breadth (95% prediction ellipse areas) and overlap of the two shearwater species during 2014, 2015 and 2016. Capelin availability varied among years, illustrated by lower peak biomass in 2015 (0.126 g/m²) and 2016 (0.027 g/m²) relative to 2014 (0.254 g/m²). The isotopic niche breadth (plasma) of both shearwater species expanded similarly from 2014 (0.65–0.66‰²) to 2015 (2.22–2.57‰²) and 2016 (1.15–1.42‰²), suggesting the incorporation of alternative prey types into their diet during years of lower prey availability. Isotopic niche overlap between Great and Sooty Shearwaters remained high across years (44–63%), however, providing little evidence for dietary niche partitioning during years of lower prey availability. Findings suggest that both shearwater species are flexible foragers and can modify their diet during the non-breeding season to accommodate fluctuations in prey availability.     

The breeding biology of Rose-ringed Parakeets Psittacula krameri in England during a period of rapid population expansion

Capsule The reproductive rate of Rose-ringed Parakeets in the UK was higher in 2001-2003 than previously estimated.

Aim To measure reproductive rate and the factors affecting this in Rose-ringed Parakeets in England during a period of rapid expansion in population of this potential invasive species.

Methods During 2001–2003, 108 nests were located and monitored in southwest London, southeast London and the Isle of Thanet. Nest survival using the Mayfield method, fledging success and the characteristics of the nest and surrounding vegetation were measured.

Results The mean date of first egg was 26 March?±?1.3 days and the median clutch size was 4 eggs. Mayfield nest survival rate was 72%. Reproductive success was 1.4?±?0.3 young fledged per nest. Parakeets bred predominantly in ash (Fraxinus) and oak (Quercus). Nest trees had a diameter at breast height (DBH) of 73.7?±?4.7?cm (mean?±?se).

Conclusion Reproductive success in this parakeet was higher than previously estimated (0.8 young fledged per nest prior to 1999). This reproductive output is sufficient to explain the rapid increase in Rose-ringed Parakeet numbers (from an estimated 1500 birds in 1996 to nearly 10,000 birds by 2004) if Rose-ringed Parakeets have a low death rate similar to other parrots.     

Fledging success of little auks in the high Arctic: do provisioning rates and the quality of foraging grounds matter?

Long-lived birds often face a dilemma between self-maintenance and reproduction. In order to maximize fitness, some seabird parents alternate short trips to collect food for offspring with long trips for self-feeding (bimodal foraging strategy). In this study, we examined whether temporal and spatial variation in the quality of foraging grounds affect provisioning and fledging success of a long-lived, bimodal forager, the little auk (Alle alle), the most abundant seabird species in the Arctic ecosystem. We predicted that an increase in sea surface temperature (SST), with an associated decrease in the preferred Arctic zooplankton prey, would increase foraging trip durations, decrease chick provisioning rates and decrease chick fledging success. Chick provisioning and survival were observed during three consecutive years (2008–2010) at two colonies with variable foraging conditions in Spitsbergen: Isfjorden and Magdalenefjorden. We found that a change in SST (range 1.6–5.4 °C) did not influence trip durations or provisioning rates. SST was, however, negatively correlated with the number of prey items delivered to a chick. Furthermore, provisioning rates did not influence chick’s probability to fledge; instead, SST was also negatively correlated with fledging probability. This was likely related to the prey availability and quality in the little auk’s foraging grounds. Our findings suggest that predicted warmer climate in the Arctic will negatively influence the ability of parents to provide their chicks, and consequently, the fledging prospects of little auk chicks.     

Linking life history traits in successive phases of a complex life cycle: effects of larval biomass on early juvenile development in an estuarine crab, Chasmagnathus granulata

In marine benthic invertebrates with complex life cycles, recruitment success, juvenile survival, and growth may be affected by variation in both maternal factors and environmental conditions prevailing during preceding embryonic or larval development. In an estuarine crab, Chasmagnathus granulata, previous investigations have shown that initial larval biomass is positively correlated with the biomass of recently extruded eggs, and it depends also on the salinity experienced during embryogenesis. Biomass at hatching has consequences for the subsequent larval development which, in this species, comprises two alternative developmental pathways with four or five zoeal instars (short or long pathway) and a megalopa. Larvae hatching with a lower than average biomass tend to develop through the long pathway and metamorphose to megalopae with higher biomass. In the present study, we show experimentally that the long pathway produces also significantly larger juveniles (crab size measured as carapace width, biomass as dry mass, carbon and nitrogen contents). Compared with juveniles originating from the short pathway, those from the long pathway showed in successive instars longer moulting cycles and larger carapace width, but lower size increments at ecdysis. In consequence, differences in size or biomass of long pathway vs short pathway crabs tended to disappear in later instars (after stage V). Furthermore, we tested in juveniles the tolerance of starvation at three salinities (5‰, 15‰, 32‰). Tolerance of starvation was significantly higher in juveniles originating from the long pathway, indicating higher energy reserves. While salinity played only a minor role for survival, it exerted significant effects on the time of moulting to the second juvenile instar, regardless of the preceding developmental pathway. The biomass of first juveniles obtained from the short pathway showed a significant positive correlation with the biomass of the freshly hatched zoea I, but not in those from the long pathway. In conclusion, the fitness of juvenile C. granulata is linked with previous developmental processes and environmental conditions during the embryonic and larval phase. Hence, a better understanding and prediction of the recruitment success of marine benthic invertebrates with a complex life cycle may require more comprehensive life‐history investigations.