Nest predation and trampling as management risks in grazed coastal meadows

Livestock grazing is an important management tool of agri-environment schemes initiated within the European Union to maintain and restore biodiversity of grassland birds. However, grazing can affect bird populations negatively by depressing reproduction through nest trampling and increasing nest predation. These effects are, however, considered low when using recommended stocking rates. By simulating wader nests, we experimentally quantify and examine the causes of variation in trampling rates on managed Baltic coastal meadows. Secondly, we examine whether livestock presence increases nest predation of one management target, the critically endangered southern dunlin (Calidris alpina schinzii). Trampling rates of experimental nests were high. Only 21% of nests would have survived a three week incubating period early in the grazing season. Trampling rates were most severe at the onset of grazing and decreased with time. Thus, timing of grazing plays a crucial role in determining breeding success on managed meadows. Predation rates of dunlin nests were moderate and did not depend on livestock presence suggesting that incubating dunlin are not disturbed by cattle. While grazing is vital in habitat restoration and in conserving grassland biodiversity, our results suggest that grazing may also threaten the viability of populations if negative effects are underestimated. Therefore, management plans, especially for endangered species, should not only rely on general recommendations on stocking rates but instead planners need to evaluate the significance of negative effects in terms of local conditions (timing of breeding and grazing, space use of cattle and birds, measured trampling rates) and adjust grazing practises accordingly.     

Light grazing of saltmarshes is a direct and indirect cause of nest failure in Common Redshank Tringa totanus

The Common Redshank Tringa totanus breeding population on British saltmarshes has declined by over 50% since 1985, with declines linked to changes in grazing management. Conservation initiatives have encouraged low‐intensity grazing of less than one cattle per hectare, but Redshank have continued to decline, even in regions where light grazing was predominant. This study quantified effects of grazing intensity on Redshank nest survival over six lightly grazed saltmarshes with livestock densities between 0 and 0.82 cattle per hectare, in the Ribble Estuary, northwest England. We assessed whether grazing resulted in nest mortality directly through cattle trampling and/or indirectly through grazer modification of habitat that accelerates predation risks. Cattle density was recorded both during the Redshank breeding season and for 1 year prior to the study, to account for both short‐term trampling effects and the longer term effects on vegetation. Results showed that risk of nest loss to trampling increased from 16% at 0.15 cattle per hectare to 98% at 0.82 cattle per hectare in the breeding season. The risk of a nest being predated increased from 28% with no grazing to 95% at 0.55 cattle per hectare based on all year grazing data. These results suggest that even light conservation grazing at less than one cattle per hectare can reduce Redshank nest survival rates to near zero. It may therefore be appropriate to reduce saltmarsh grazing intensities, or change the timing of saltmarsh grazing to reduce the number of livestock present during the Redshank breeding season.     

Nest trampling and ground nesting birds: Quantifying temporal and spatial overlap between cattle activity and breeding redshank

Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low‐intensity grazing at <1 cattle/ha, but even these levels of grazing can result in high levels of nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications: Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid‐April and mid‐July when nests are active, through delaying the onset of grazing or introducing a rotational grazing system.     

Age‐dependent dispersal and habitat choice in black‐tailed godwits Limosa limosa limosa across a mosaic of traditional and modern grassland habitats

Whether to disperse, and where to, are two of the most prominent decisions in an individual's life, with major consequences for reproductive success. We studied natal and breeding dispersal in the monogamous black‐tailed godwit Limosa limosa limosa in the Netherlands, where they breed in agricultural grasslands. The majority of these grasslands recently changed from wet herb‐rich meadows into well‐drained grassland monocultures, on which godwits have a lower reproductive success. Here we examine habitat selection with a multistate mark–recapture analysis. Habitat transition probabilities between meadows and monocultures were estimated on the basis of 1810 marked chicks and 531 adults during seven years in a 8500 ha study area. Young and adult godwits may differ in habitat selection because: 1) adults may have gained experience from previous nest success where to settle, 2) younger individuals may find it harder to compete for the best territories. Both young and adults moved at a higher rate from the predominant monocultures to meadows than the other way around, thus actively selecting the habitat with better quality. However, dispersal distance of adults was not affected by previous nest success. The average dispersal distance from place of birth of godwits breeding for the first time was ten times larger than that of adult godwits. That godwits breeding in their second calendar year arrived and laid at similar dates and were equally able to select territories in areas with high breeding densities, suggests that young birds were not competitively inferior to adults. Although on monocultures reproduction is insufficient to maintain constant populations, birds sometimes moved from meadows to monocultures. This explains why even after 30 years of land‐use intensification, godwits still breed in low‐quality habitat. The adjustment to changing habitat conditions at the population level appears to be a slow process.     

Management of modern agricultural landscapes increases nest predation rates in Black‐tailed Godwits Limosa limosa

Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb‐rich meadows has been replaced by grassland monocultures. The timing of agricultural activities in these monocultural grasslands is critical, as they often coincide with the nesting phase of breeding birds. Here, we aim to identify the effect of habitat management and targeted nest protection on nest survival of Black‐tailed Godwits Limosa limosa in the Netherlands, a population that has shown a 70% reduction in breeding population size since the 1970s. To protect nests in monocultures from destruction, farmers are paid to either delay mowing or leave a patch of unmown grass around the nest, a patch which in practice varied in size. In herb‐rich meadows, which are typically managed for bird conservation purposes, mowing occurs after hatching. Nest survival declined as the season advanced, more steeply on monocultures than on meadows. Targeted nest protection was only partially successful, as nest predation was considerably higher on mown grassland monocultures with small unmown patches around the nest than in mown monocultures with large unmown patches and in unmown fields. Increased predator densities over the years have been suggested as an important cause of the trend towards lower nest survival, but here we show that nest survival was higher on herb‐rich meadows than on monocultures, and similar to the 1980s. It thus seems that increased predator densities are an increased threat during the egg stage only if habitat quality is low. High‐quality habitat in the form of herb‐rich meadows therefore provides a degree of protection against predators.     

Habitat suitability and demography,a time‐dependent relationship

The habitat suitability index, which reflects spatial variability in species occurrence probability, has been shown to exhibit various contrasting relationships with local demographic performances (survival, productivity) in several species. One proposed explanation for these discrepancies is that the link between the habitat suitability index and demography is influenced by density‐dependent, temporally variable processes. Based on the survival rates of more than 3,000 nests monitored over 12 years in the North African Houbara Bustard, we investigated whether the habitat suitability index computed over the species breeding range is related to nest survival throughout the breeding season, accounting for variation in meteorological conditions. We found that the relationship between the habitat suitability index and nest survival progressively changes along the breeding season and that this intra‐annual variation is consistent between years. Our results support the hypothesis that variation in space use occurs intra‐annually and that biotic interactions throughout the breeding season strongly influence the habitat suitability index–demography relationship.     

Is the large‐scale decline of the starling related to local changes in demography?

The decline of one farmland bird, the migratory European starling, has been attributed to both agricultural intensification and farmland abandonment and to factors operating both during the winter and during the breeding season. We analysed population data from thirty‐three Swedish nestbox colonies over more than two decades to determine if the national decline was caused by a common factor affecting all colonies or by local changes in the breeding grounds affecting starling colonies. We found that numbers of breeding starling had declined significantly, but at different rates in different colonies. The local population sizes were affected by previous years’ productivity at both national and local scales, suggesting that changes in habitat quality at both scales could affect local population trends. There were no long‐term trends in reproductive output, but fledgling production was lowest at intermediate years. The local population changes were positively related to local changes in reproductive output, but only when including complete nest‐failures. A relationship between population declines and low mean local productivity was the result of the association between population sizes and reproductive success over time, since decline rates of starlings were not related to the average success during the first part of the study, but to the average success during the later part of the study. The relationship between population change and changes in reproductive output was evident, but fledgling production showed negative density‐dependence. In conclusion this study suggests that the decline of the starling population in Sweden has been affected by processes at small spatial scales during the breeding season affecting reproductive success, but does not exclude an additional role for processes at large spatial scales or outside the breeding season.     

Rapid response of a long-lived species to improved water and grazing management: The case of the European pond turtle (Emys orbicularis) in the Camargue,France

Among human activities, the effect of habitat management by grazing on population viability is ambiguous. Indeed, beneficial effects of grazing are expected by maintaining open meadows, but overgrazing is supposed to increase mortality by trampling. Grazing has been shown to negatively impact the survival of European pond turtle (Emys orbicularis) in the Camargue. Consequently, a new management plan was defined. We investigated the consequences of this management using capture–recapture methods to estimate variations of population sizes in this managed site and a control site over a 17 years period. Results show an increase of the number of adults and juveniles on the managed site after the management change. Our results suggest that improved water management with flooding in autumn provided better hibernation conditions, and that reduced grazing intensity in autumn/winter likely decreased the risk of trampling. Population size significantly increased in less than 4 years following the management change, probably by the relaxation of density-dependence. It is an original result for a long lived-species supposed to have an important time of resilience to perturbations.     

Nesting in an uncertain world: information and sampling the future

Seasonal fecundity is strongly influenced by the number of nests attempted (including renests following nest failure) in a season. This number is often assumed to be set by the length of the breeding season or through some predetermined maximum. Instead, the decision to renest likely results from a cost–benefit analysis honed by natural selection where the ultimate components of fitness, i.e. reproduction and survival, tradeoff with one another. Moreover, reproductive decision making should not occur in an information‐vacuum. In a world where habitat quality (i.e. likelihood of nest success) is uncertain females should use nest failures to update the probability their renest nest will succeed, and this estimate in turn can affect the decision to renest. We develop a model of renesting behavior based on these conceptual ideas using the framework of statistical decision theory (SDT) and the process of Bayesian updating. We assume that renesting incurs 1) a cost to future reproductive success and 2) a reduction in expected reproductive success for each successive replacement nest. We show, all else equal, birds should curtail renesting with (1) increased residual reproductive success, (2) increased cost to future reproduction, (3) declines in current reproduction with successive attempts, and (4) increasing nest predation rates. We also explore several ecological implications of the model. First, uncertainty in habitat quality and the process of information updating, based on nest outcomes, link changes in the quality or proportion of one habitat type to the behavior in the other habitat. Second, females may use their estimate of habitat quality, based on a sample of nesting attempts, to decide whether to return or disperse to a new site between years. We compare this to the win‐stay: lose‐switch rule for dispersal and discuss the implications for population dynamics.     

Causes of variable reproductive performance by Southern Ground‐hornbill Bucorvus leadbeateri and implications for management

Range occupancy of the cooperatively breeding Southern Ground‐Hornbill Bucorvus leadbeateri in South Africa has decreased by 65% in the last three generations and the effective management of the remaining populations is hampered by a lack of fundamental understanding of the factors determining reproductive performance. We examined the influence of social and environmental factors on the species' reproductive success in South Africa using data gathered from 23 groups over eight breeding seasons. Some groups had access to artificial nest‐sites, others did not. High rainfall (> 500 mm) over the breeding season led to a decrease in reproductive success, with groups being most successful in years when rain in the vicinity of the nest ranged from 300 to 500 mm. Groups breeding in natural nests were successful only when the proportion of open woodland surrounding the nest‐site was high. Those that bred in artificial nests, where overall breeding success was more than twice as high as those in natural nests, were less dependent on the availability of open woodland. Large groups (more than three birds) bred more successfully than groups comprising only two to three individuals. Group size, helper effects and rainfall cannot be managed to increase the productivity of Ground‐Hornbills but the fact that the availability of artificial nest‐sites and the amount of open woodland around the nest‐site both contribute positively to breeding performance identifies practical and simple management options for increasing the reproductive output of Southern Ground‐Hornbill populations.     

Group composition and reproductive success of cooperatively breeding white‐winged choughs (Corcorax melanorhamphos) in urban and non‐urban habitat

Abstract: White‐winged choughs (Corcorax melanorhamphos, Corcoracidae) are a common, breeding resident in and around the city of Canberra in the Australian Capital Territory. We compared five measures of reproductive success between the urban and non‐urban populations of choughs to investigate the effect of urbanization on this cooperatively breeding species. Urban choughs initiated breeding earlier than their non‐urban counterparts and were more likely to suffer nest failures. However, there was no difference in the number of successful nests in a season or the number of fledglings produced per successful nesting attempt. A greater proportion of fledglings survived their first 12 months in the non‐urban habitat. We suggest that increased rates of nest predation and fledgling mortality in the urban environment may have a negative effect on reproductive success and remove any advantage that might be gained through a longer breeding season. Possible effects of urbanization on the social and genetic structure of white‐winged choughs are also discussed.     

Seasonal variation in male alternative reproductive tactics

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

Nesting success in Redshank Tringa totanus breeding on coastal meadows and the importance of habitat features used as perches by avian predators

Capsule Nest survival rates could not be explained by distance to habitat edges or other features used by predators.

Aims To investigate if predation on Redshank nests was affected by habitat characteristics at a local scale.

Methods We examined survival rates of Redshank nests on coastal meadows on the Baltic island of Gotland, Sweden, over two breeding seasons. We analysed nest survival rates in relation to several habitat characteristics that may benefit predators searching for nests. We examined existing studies concerning predation rates on wader nests in relation to edges and habitat features potentially used by avian predators.

Results We found no significant effects of distance to habitat edge or to nearest potential lookout for avian predators or to shoreline. Abundance of Lapwings Vanellus vanellus, an aggressive species with active nest-defence, did not have any significant effect on nest survival rate, nor did vegetation concealment of nests. Nest survival rates were significantly different between years and lower later in the season.

Conclusions There is only weak support for general effects on wader nest predation rates of proximity to edges and features used by avian predators. Simple mechanical management actions such as removal of trees and bushes on coastal meadows may not directly, and by itself, result in higher reproductive success of waders. Further understanding is needed of the behaviour of predators and the composition of the predator community in different landscapes in order to increase the efficiency of management actions to remove threats to vulnerable species on coastal meadows.     

Remotely sensed forest understory density and nest predator occurrence interact to predict suitable breeding habitat and the occurrence of a resident boreal bird species

Habitat suitability models (HSM) based on remotely sensed data are useful tools in conservation work. However, they typically use species occurrence data rather than robust demographic variables, and their predictive power is rarely evaluated. These shortcomings can result in misleading guidance for conservation. Here, we develop and evaluate a HSM based on correlates of long‐term breeding success of an open nest building boreal forest bird, the Siberian jay. In our study site in northern Sweden, nest failure of this permanent resident species is driven mainly by visually hunting corvids that are associated with human settlements. Parents rely on understory nesting cover as protection against these predators. Accordingly, our HSM includes a light detection and ranging (LiDAR) based metric of understory density around the nest and the distance of the nest to the closest human settlement to predict breeding success. It reveals that a high understory density 15–80 m around nests is associated with increased breeding success in territories close to settlements (<1.5 km). Farther away from human settlements breeding success is highest at nest sites with a more open understory providing a favorable warmer microclimate. We validated this HSM by comparing the predicted breeding success with landscape‐wide census data on Siberian jay occurrence. The correlation between breeding success and occurrence was strong up to 40 km around the study site. However, the HSM appears to overestimate breeding success in regions with a milder climate and therefore higher corvid numbers. Our findings suggest that maintaining patches of small diameter trees may provide a cost‐effective way to restore the breeding habitat for Siberian jays up to 1.5 km from human settlements. This distance is expected to increase in the warmer, southern, and coastal range of the Siberian jay where the presence of other corvids is to a lesser extent restricted to settlements.     

Sprague's pipit breeding biology and reproductive success in planted and native grasslands

Much of the native grasslands in agricultural regions have been converted to cropland or tilled and seeded with non‐native grasses for livestock production. Several grassland songbird species occupy planted grasslands, but occupancy or density may not be a reliable indicator of habitat quality. I studied the breeding biology of Sprague's pipit Anthus spragueii from 2004 to 2008 in Saskatchewan, Canada. My objective was to determine the extent to which the breeding biology, density and reproductive success of pipits varied in planted and native grasslands. Peak clutch initiation occurred in mid‐ to late‐May in planted and native grassland. Peak pipit density also occurred in May, but density drastically declined over the breeding season in planted grassland. Clutch size varied among years and declined over the breeding season, but was similar in planted (4.7  0.1 SE) and native grasslands (4.5  0.1 SE). Daily nest survival rates varied with age of the nest and date, but the relationships differed in the two habitats and was likely a result of lower nestling survival in planted grassland compared to native grassland. The number of young fledged per nest increased as the season progressed and tended to be greater in native (1.2  0.1 SE) than planted (0.9  0.2 SE) grasslands. Seasonal productivity was much greater in native grassland. Only three nests were initiated after May in planted grassland and all were unsuccessful, whereas pipit young fledged at higher rates from nests initiated in native grassland in June and July than planted grassland nests initiated in May. The number of fledged young from successful nests did not vary strongly with habitat, date or year. This research indicates that planted grasslands attract pipits at the beginning of the breeding season, but habitat suitability and reproductive success substantially declines as the breeding season progresses compared to that found in native grassland.     

Spatio‐temporal variation in European starling reproductive success at multiple small spatial scales

Understanding population dynamics requires spatio‐temporal variation in demography to be measured across appropriate spatial and temporal scales. However, the most appropriate spatial scale(s) may not be obvious, few datasets cover sufficient time periods, and key demographic rates are often incompletely measured. Consequently, it is often assumed that demography will be spatially homogeneous within populations that lack obvious subdivision. Here, we quantify small‐scale spatial and temporal variation in a key demographic rate, reproductive success (RS), within an apparently contiguous population of European starlings. We used hierarchical cluster analysis to define spatial clusters of nest sites at multiple small spatial scales and long‐term data to test the hypothesis that small‐scale spatio‐temporal variation in RS occurred. RS was measured as the number of chicks alive ca. 12 days posthatch either per first brood or per nest site per breeding season (thereby incorporating multiple breeding attempts). First brood RS varied substantially among spatial clusters and years. Furthermore, the pattern of spatial variation was stable across years; some nest clusters consistently produced more chicks than others. Total seasonal RS also varied substantially among spatial clusters and years. However, the magnitude of variation was much larger and the pattern of spatial variation was no longer temporally consistent. Furthermore, the estimated magnitude of spatial variation in RS was greater at smaller spatial scales. We thereby demonstrate substantial spatial, temporal, and spatio‐temporal variation in RS occurring at very small spatial scales. We show that the estimated magnitude of this variation depended on spatial scale and that spatio‐temporal variation would not have been detected if season‐long RS had not been measured. Such small‐scale spatio‐temporal variation should be incorporated into empirical and theoretical treatments of population dynamics.     

Columbian sharp-tailed grouse female and nest survival in northwestern Colorado

Wildlife management and conservation can be challenging when the demography of a focal species is unknown or limited given that fecundity and adult survival influence population growth. The Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) have been reduced to ≤10% of their former range since the early 1900s. We conducted a 3-year study (2015–2017) across 4 study sites in northwestern Colorado, USA, to evaluate female hazard and nest survival. We trapped and marked 270 female sharp-tailed grouse and identified 275 nests for our hazard and survival analyses. Females during the breeding stage of the reproductive season experienced more hazard compared to the nesting and the early and late post-nesting stages for females without broods. Females experienced a higher degree of hazard during the breeding stage and mortality risk was >3 times higher than the nesting stage, >7 times higher than early post-nesting (EPN)-no brood stage, and >5 times higher than the late post-nesting (LPN)-unsuccessful stage. Two reproductive season stages (LPN-successful and EPN-brood) provided marginal inference. Nest incubation initiation date and nest age best described nest daily survival. Females that initiated incubation of initial nests earlier in the season experienced lower nest daily survival than later in the incubation season. Because female Columbian sharp-tailed grouse hazard varied among different reproductive season stages, we recommend that wildlife managers develop management actions that reduce hazard during the specific reproductive season stages (i.e., the breeding season). For Columbian sharp-tailed grouse in Colorado, we recommend that Colorado Parks and Wildlife collaborate with federal farm program agencies to implement a no-tillage restriction from 1 May through 30 June for active agricultural fields within 2 km of active Columbian sharp-tailed grouse leks to enhance nest survival.     

Immigration stabilizes a population of threatened cavity‐nesting raptors despite possibility of nest box imprinting

Nest box provisioning is a common management tool intended to increase population size or stability of threatened birds, but its effectiveness is rarely assessed. The provisioning of nest boxes may lead to unexpected results if nest type imprinting prevents naïve adult birds from immigrating into the nest box population, or limiting the ability of juveniles reared in nest boxes to emigrate to areas with only natural nesting substrates. We analyzed the population trends from 2008 to 2010 of southeastern American kestrels Falco sparverius paulus associated with a network of nest boxes in north‐central Florida, USA, with Bayesian integrated population models (IPMs) that simultaneously considered mark–recapture data sets, fledgling production, and population surveys. We evaluated the demography of the nest box population by comparing population growth rates, apparent survival probabilities, and recapture probabilities between an IPM that explicitly modeled immigration and one that did not. Overall population growth rates suggested that the population was stable, and that immigration was apparently important in maintaining this stability, with approximately 0.3 and 0.5 female immigrants per resident female kestrel each year. Explicitly modeling immigration resulted in lower estimates of juvenile kestrel apparent survival probability, suggesting that a large proportion of locally produced juveniles emigrated rather than recruited locally. We concluded that neither preference for natural cavities nor imprinting on artificial nest boxes appeared to prevent immigration from maintaining the stability of the local population. Natal habitat preference imprinting on nest sites may occur to some degree, but it did not preclude the adoption of nest boxes by most breeding kestrels. We also found additional indications that many juvenile kestrels fledged from nest boxes emigrated to the surrounding natural areas.     

Human-resource subsidies alter the dietary preferences of a mammalian top predator

Seasonal fitness declines are common, but the relative contribution of different reproductive components to the seasonal change in the production of reproductive young, and the component-specific drivers of this change is generally poorly known. We used long-term data (17 years) on breeding time (i.e. date of first egg laid) in northern wheatears (Oenanthe oenanthe) to investigate seasonal reproductive patterns and estimate the relative contributions of reproductive components to the overall decline in reproduction, while accounting for factors potentially linked to seasonal declines, i.e. individual and habitat quality. All reproductive components—nest success (reflecting nest predation rate), clutch size, fledging success and recruitment success—showed a clear decline with breeding time whereas subsequent adult survival did not. A non-linear increase in nest predation rate caused nest success to decline rapidly early in the season and level off at ~80 % success late in the breeding season. The combined seasonal decline in all reproductive components caused the mean production of recruits per nest to drop from around 0.7–0.2; with the relative contribution greatest for recruitment success which accounted for ~50 % of the decline. Our data suggest that changing environmental conditions together with effects of nest predation have strong effects on the seasonal decline in fitness. Our demonstration of the combined effects of all reproductive components and their relative contribution shows that omitting data from later stages of breeding (recruitment) can greatly underestimate seasonal fitness declines.     

3. THE GOLDEN ORIOLE (Oriolus oriolus) IN HOLLAND

Even though Sfax salina in Tunisia hosts a significant part of the Mediterranean population of Pied Avocet Recurvirostra avosetta, data on the breeding ecology of this species in this area are lacking. Such data are nonetheless necessary, not only for the understanding of the ecology and dynamics of this species in general, but also for conservation purposes. In this paper we use the results of a one-year monitoring of nests in Sfax salina to provide information on its nesting parameters, in particular nesting phenology, colony size and hatching success. Our results show that Pied Avocets formed dense colonies at the beginning of the nesting season, but colony size decreased as the nesting season advanced. Clutch size varied between 1 and 7 eggs, similar to other Mediterranean and European populations. Hatching success, estimated by the Mayfield method, was relatively low, mainly due to predation by stray dogs. Overall, our work shows that relatively high nest losses occur here. It also highlights the need for management efforts aiming to enhance the reproductive success in this artificial habitat. Creation of suitable and safe nesting sites is proposed.