Number Of Fledglings Research Articles

Double-brooding and annual breeding success of great tits in urban and forest habitats.

Urban areas differ from natural habitats in several environmental features that influence the characteristics of animals living there. For example, birds often start breeding seasonally earlier and fledge fewer offspring per brood in cities than in natural habitats. However, longer breeding seasons in cities may increase the frequency of double-brooding in urban compared with nonurban populations, thus potentially increasing urban birds' annual reproductive output and resulting in lower habitat difference in reproductive success than estimated by studies focusing on first clutches only. In this study, we investigated 2 urban and 2 forests great tit Parus major populations from 2013 to 2019. We compared the probability of double-brooding and the total number of annually fledged chicks per female between urban and forest habitats, while controlling for the effects of potentially confounding variables. There was a trend for a higher probability of double-brooding in urban (44% of females) than in forest populations (36%), although this was not consistent between the 2 urban sites. Females produced significantly fewer fledglings annually in the cities than in the forest sites, and this difference was present both within single- and double-brooded females. Furthermore, double-brooded urban females produced a similar number of fledglings per season as single-brooded forest females. These results indicate that double-brooding increases the reproductive success of female great tits in both habitats, but urban females cannot effectively compensate in this way for their lower reproductive output per brood. However, other mechanisms like increased post-fledging survival can mitigate habitat differences in reproductive success.

Nonideal nest box selection by tree swallows breeding in farmlands: Evidence for an ecological trap?

Animals are expected to select a breeding habitat using cues that should reflect, directly or not, the fitness outcome of the different habitat options. However, human‐induced environmental changes can alter the relationships between habitat characteristics and their fitness consequences, leading to maladaptive habitat choices. The most severe case of such nonideal habitat selection is the ecological trap, which occurs when individuals prefer to settle in poor‐quality habitats while better ones are available. Here, we studied the adaptiveness of nest box selection in a tree swallow (Tachycineta bicolor) population breeding over a 10‐year period in a network of 400 nest boxes distributed along a gradient of agricultural intensification in southern Québec, Canada. We first examined the effects of multiple environmental and social habitat characteristics on nest box preference to identify potential settlement cues. We then assessed the links between those cues and habitat quality as defined by the reproductive performance of individuals that settled early or late in nest boxes. We found that tree swallows preferred nesting in open habitats with high cover of perennial forage crops, high spring insect biomass, and high density of house sparrows (Passer domesticus), their main competitors for nest sites. They also preferred nesting where the density of breeders and their mean number of fledglings during the previous year were high. However, we detected mismatches between preference and habitat quality for several environmental variables. The density of competitors and conspecific social information showed severe mismatches, as their relationships to preference and breeding success went in opposite direction under certain circumstances. Spring food availability and agricultural landscape context, while related to preferences, were not related to breeding success. Overall, our study emphasizes the complexity of habitat selection behavior and provides evidence that multiple mechanisms may potentially lead to an ecological trap in farmlands.

The effect of local weather conditions and nest box location on the reproduction of the Common Kestrel (Falco tinnunculus) in the farmland of eastern Poland

Artificial nests like nest boxes are commonly used to improve the reproductive output and population status of wild birds and advance our understanding of their evolutionary ecology. To investigate how the location of nest boxes and local weather conditions affect Common Kestrel reproduction (number of fledglings), 319 broods from 173 nest boxes in east-central Poland were examined. Of the six meteorological parameters analysed, only mean temperature and maximum temperature were selected as the best model. Mean daily temperature had a positive effect but maximum temperature a negative one on Common Kestrel reproduction. The first egg laying date was negatively correlated with the number of fledglings. Contrary to the assumption that trees should offer a superior microclimate in the canopy, nest boxes placed on utility poles have the same numbers of fledglings. The area of the main habitat type is not decisive in Common Kestrel productivity either. These findings may be helpful for ongoing conservation programmes and confirm that utility poles should be the preferred form of deployment of nest boxes as they are easier to monitor and maintain.

Reproductive consequences of material use in avian nest construction

Birds’ nests represent a rich behavioural ‘fingerprint’, comprising several important decisions—not the least of which is the selection of appropriate material. Material selection in nest-building birds is thought to reflect, in part, builder-birds’ use of the ‘best’ material—in terms of physical properties (e.g., rigidity)—refined across generations. There is, however, little experimental evidence to link the physical properties of nest material to both birds’ nest-building and breeding performance. We examined individual-level material-use consequences for breeding zebra finches by manipulating the kind of material available to laboratory-housed pairs: stiff or flexible same-length string. We show that higher fledgling numbers were related to: (i) fewer pieces used in nest construction by stiff-string builders; and conversely, (ii) more pieces used in nest construction by flexible-string builders. Together, these data suggest that physical differences in nest material can affect avian reproduction (here, the trade-off between nest-construction investment and fledgling success), highlighting the adaptive significance of nest-building birds’ material selectivity.

Natural variation in yolk fatty acids, but not androgens, predicts offspring fitness in a wild bird

BackgroundIn egg-laying animals, mothers can influence the developmental environment and thus the phenotype of their offspring by secreting various substances into the egg yolk. In birds, recent studies have demonstrated that different yolk substances can interactively affect offspring phenotype, but the implications of such effects for offspring fitness and phenotype in natural populations have remained unclear. We measured natural variation in the content of 31 yolk components known to shape offspring phenotypes including steroid hormones, antioxidants and fatty acids in eggs of free-living great tits (Parus major) during two breeding seasons. We tested for relationships between yolk component groupings and offspring fitness and phenotypes.ResultsVariation in hatchling and fledgling numbers was primarily explained by yolk fatty acids (including saturated, mono- and polyunsaturated fatty acids) - but not by androgen hormones and carotenoids, components previously considered to be major determinants of offspring phenotype. Fatty acids were also better predictors of variation in nestling oxidative status and size than androgens and carotenoids.ConclusionsOur results suggest that fatty acids are important yolk substances that contribute to shaping offspring fitness and phenotype in free-living populations. Since polyunsaturated fatty acids cannot be produced de novo by the mother, but have to be obtained from the diet, these findings highlight potential mechanisms (e.g., weather, habitat quality, foraging ability) through which environmental variation may shape maternal effects and consequences for offspring. Our study represents an important first step towards unraveling interactive effects of multiple yolk substances on offspring fitness and phenotypes in free-living populations. It provides the basis for future experiments that will establish the pathways by which yolk components, singly and/or interactively, mediate maternal effects in natural populations.

Ecological traps: evidence of a fitness cost in a cavity-nesting bird

Habitat quality has direct effects on the evolutionary fitness of breeding organisms, which is why it is believed that animals tend to have an evolved preference for the best possible habitats. However, some animals may mistakenly choose to reproduce in habitats that decrease their fitness, resulting in ‘ecological traps’. In this study, we tested whether great tits (Parus major) attracted to areas affected by outbreaks of the great web-spinning sawfly (Acantholyda posticalis) had fitness detriments characteristic of ecological traps. Sawfly larvae consume pine needles, which decreases resource availability for birds co-habiting the forest. Using artificial nesting sites, we found that great tits inhabiting areas of sawfly outbreaks had similar clutch sizes as tits breeding in healthy forest patches; however, the fledgling number was significantly lower, and fledgling condition was worse in the damaged forests. While moth larvae are the most important food for bird nestlings, the forest patches damaged by sawflies had lower larval biomass. Although most ecological traps occur in environments altered by humans, this study shows that pest insects can lower habitat quality, forming ecological traps. Our results indicate that attracting cavity-nesting birds should be done with caution because it may negatively impact birds’ nutritional status and reproductive fitness.

Long-Term Population Fluctuations of a Burrowing Owl Population on Kirtland Air Force Base, New Mexico, USA

Western Burrowing Owls (Athene cunicularia hypugaea; hereafter, Burrowing Owls) were once widespread residents of grasslands throughout western North America, but their range has contracted, and abundance has declined in some regions. The causes of declines and geographic variation in population trends of Burrowing Owls are unclear but may be linked to changing land use and urbanization. Burrowing Owls are often found in association with airfields and airports, and their presence at such facilities is sometimes considered to be in conflict with those operations. Documenting the long-term persistence of Burrowing Owls at active airfields can help airfield managers who face decisions regarding compatibility of owls and airfield operations. We report the results of a long-term effort to monitor Burrowing Owls on Kirtland Air Force Base in New Mexico, USA, including the rapid recovery of Burrowing Owl numbers from near-extirpation and the relationships between abundance and other demographic traits. The number of breeding pairs of Burrowing Owls increased from one pair in 2013 to 28 pairs in 2019 and 2020, and the number of fledglings produced increased from one in 2013 to 84 in 2019 and 61 in 2020. The recovery was not uniform across all areas of Kirtland Air Force Base, and some formerly occupied areas remained unoccupied. We documented dispersal outside the Air Force base boundary and that the number of breeding pairs was more strongly influenced by the number of offspring produced in the prior year than the number of owls returning from prior years, which indicated that the population is part of a larger meta-population. Our results demonstrate that the maintenance of Burrowing Owl populations is not necessarily at odds with safe airfield operations, that Burrowing Owls exhibit complex population dynamics, and can rapidly recolonize previously occupied areas if habitat and nest sites remain suitable.

The effect of Natura 2000 network on the Eurasian Eagle-owl (Bubo bubo) population in Southeast Bulgaria: implications for conservation

Abstract The effectiveness and efficiency of the Natura 2000 network for the Eurasian Eagle-owl conservation in SE Bulgaria was assessed by comparing data collected during a long-term study on number of breeding pairs and fledglings before and after network establishment. The Natura 2000 network and non-protected areas showed similar values of the calculated indices according to the number of occupied localities. However, the pairs in Natura 2000 sites bred significantly less fledglings after the creation of the network than the pairs in non-protected ones. The Special Protection Areas (SPA) system created specifically for the preservation of birds has the lowest efficiency in respect to Eurasian Eagle-owl protection. Proposals were made after ‘gap analysis’ for real protection and optimization of the protected-area network to increase the stability of the Eurasian Eagle-owl population in the changing environment.

Breeding Ecology of the Iberian Chiffchaff Phylloscopus ibericus: First Data from North Africa

Till now, the breeding biology of several North African bird populations has been little studied, particularly that of the southern populations of Iberian chiffchaff Phylloscopus ibericus. In the present study, total of 31 nests of Iberian chiffchaff were monitored in the northeastern Algeria during 2013–2017. The nesting period, clutch and brood sizes, and reproductive success of the species were determined. The first egg-laying dates of the first broods were spread over the first twenty days of April. There were significant among-year variations in nesting seasons. The Iberian chiffchaff clutch sizes averaged 4.51 eggs. The number of hatchlings and fledglings averaged 4.09 and 3.54 nestlings, respectively. There is no correlation between the nest height above the ground and the hatching and the breeding success of the species. Predation and nest abandonment were the main causes of the breeding failure of the Iberian chiffchaff in studied population, however, in general the breeding success was high – 80.7%. Breeding data for the Iberian chiffchaff at the southern edge of its breeding range in North Africa show smaller clutches and production of fewer young compared to the common chiffchaff Phylloscopus collybita in Europe.

Sexual maturity varies with melanic plumage traits in the barn owl

The age at first reproduction can significantly impact fitness. We investigated the possible source of variation in the age at first reproduction (‘sexual maturity') and its consequences for lifetime reproductive success in a wild population of barn owls. This raptor is sexually dimorphic for two melanin‐based plumage traits shown to covary with sex‐specific behaviour and physiology. We observed that females were sexually mature earlier than males, an effect that depended on the colour of their plumage and birth date. Among females born early in the season, dark melanic (i.e. more pheomelanic with large and many black feather spots) yearlings were sexually mature earlier than light melanic females. The relationship was in the opposite direction in those born late in the season. In yearling males, the opposite result, albeit less pronounced, was discovered, i.e. lightly melanic males born early in the season were sexually mature earlier than dark melanic males, an effect that was in the opposite direction in males that were born late in the season. Individuals that matured faster produced a larger number of fledglings per year than individuals that matured slower, an effect that was found only in dark melanic females and in light melanic males. Dark melanic females also achieved a higher lifetime reproductive success (LRS) than light melanic conspecifics. Our results suggest that a light melanic plumage is beneficial in males and a dark melanic plumage in females suggesting sexually antagonist selection.

Effects of prescribed fire on fuels, vegetation, and Golden-cheeked warbler (Setophaga chrysoparia) demographics in Texas juniper-oak woodlands: An update six years post-fire

The juniper (Juniperus ashei) - oak (Quercus sp.) woodlands of central Texas are susceptible to crown fire due to climate change, land use change, and fire suppression. Low-intensity prescribed fire is one method used to reduce fuel loads and lower the risk of crown fire. Better knowledge of the impacts of prescribed fire on fuel loads, vegetation structure, and the endangered golden-cheeked warbler (Setophaga chrysoparia), a songbird that breeds exclusively in these woodlands, is needed to inform management decisions. We conducted a before-after control-impact study on three plot-pairs within Balcones Canyonlands National Wildlife Refuge, Texas, to determine the response of fuel loads, vegetation structure, and golden-cheeked warblers to prescribed fire. We measured fuel loads and vegetation structure before fire (2012), and again one year (2014) and six years (2019) after fire. We then evaluated the year × treatment interaction in each time interval to determine if there was a fire effect by fire severity score (a measure of fire impact). We found no significant year × treatment interaction on fuel loads in 2014 or in 2019, but there was a significant year × treatment interaction for juniper seedling density, juniper sapling density, non-juniper seedling density, non-juniper sapling density, canopy cover, and litter depth in one or both years. Juniper seedling and sapling density had significant declines in areas of severe fire effects in 2014, and juniper sapling density stayed lower even through 2019. Non-juniper seedling and sapling density increased dramatically in 2019 in areas that experienced severe fire effects; however, we note that the majority of sapling stems were from resprouting which is the predominate method of oak persistence in this ecosystem. Juniper seedling density, canopy cover, and litter depth all showed an interaction effect in 2014 but not in 2019, possibly indicative of recovery. We monitored golden-cheeked warblers during 2012–2014 and 2019 (although we did not determine breeding success in 2013) and found prescribed fire had varying effects on golden-cheeked warblers. There was a significant interaction for territory density in 2013 and 2014 but not in 2019; density remained similar on control plots in 2013 and 2014 but declined in 2019, whereas density declined in 2013 and 2014 but stabilized in 2019 on treatment plots. Breeding parameters were similar across time intervals, except number of fledglings per successful territory was lower on treatment plots in 2019 than 2012. Six years post-fire, golden-cheeked warblers mostly avoided areas where canopy mortality had occurred, except in woodlands categorized with a red oak-juniper canopy and a juniper understory pre-fire, where they had a relatively high probability of use in severely impacted areas. Prescribed fire achieved some management goals (e.g., lower densities of young junipers and higher densities of young oaks) but did not meaningfully reduce fuel loads in the short or intermediate time periods. Additional time is necessary to determine if oak regeneration on the treatment plots results in mature trees.

Interannual climate variation influences nest initiation date and nest productivity of the Red-cockaded Woodpecker at the northwestern edge of its range

AbstractClimate change, including directional shifts in weather averages and extremes and increased interannual weather variation, is influencing demography and distributions for many bird species. The Ouachita Mountains ecoregion in southeast Oklahoma and west-central Arkansas contains 2 populations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a federally endangered, cooperatively breeding species. Since this region is at the RCW’s northwestern range periphery, ecological thresholds likely are limiting for the species. Therefore, populations in this region may be more sensitive to climate change-associated weather variation and unpredictability. We used 26 years of nesting data (1991–2016) from the 2 RCW populations to determine if interannual weather variation has affected nesting phenology and productivity. For each population, we used daily temperature and precipitation data for 3 periods (30 and 60 days before nesting; 40 days overlapping the nesting period) to determine how weather influences median nesting date and average clutch size and numbers of fledglings. In a separate analysis, we used shorter time windows with individual nests as replicates to determine how discrete weather events (e.g., minimum and maximum temperatures and intense precipitation events) affect nest success and partial brood loss. For both Oklahoma and Arkansas populations, warmer early spring temperatures generally advanced nesting and increased clutch size and fledgling number. However, the effects of average precipitation varied depending on the amount and duration of precipitation in different time periods. At the nest level, most variables reflecting discrete temperature and precipitation events were unrelated to nest success and brood loss, suggesting that factors other than weather (e.g., habitat quality and predation) more strongly influenced the nesting output of individual RCW broods. Our results indicate RCWs are responding to interannual weather variation in complex and variable ways. However, warming trends may generally be having positive effects on the species at the northwestern edge of its range.

Phenology-mediated effects of phenotype on the probability of social polygyny and its fitness consequences in a migratory passerine

Why females engage in social polygyny remains an unresolved question in species where the resources provided by males maximize female fitness. In these systems, the ability of males to access several females, as well as the willingness of females to mate with an already mated male, and the benefits of this choice, may be constrained by the socio-ecological factors experienced at the local scale. Here, we used a 19-year dataset from an individual-monitored population of pied flycatchers (Ficedula hypoleuca) to establish local networks of breeding pairs. Then, we examined whether the probability of becoming socially polygynous and of mating with an already mated male (thus becoming a secondary female) is influenced by morphological and sexual traits as proxies of individual quality relative to the neighbours. We also evaluated whether social polygyny is adaptive for females by examining the effect of females’ mating status (polygamously-mated vs monogamously-mated) on direct (number of recruits in a given season) and indirect (lifetime number of fledglings produced by these recruits) fitness benefits. The phenotypic quality of individuals, by influencing their breeding asynchrony relative to their neighbours, mediated the probability of being involved in a polygynous event. Individuals in middle-age (2–3 years), with large wings and, in the case of males, with conspicuous sexual traits, started to breed earlier than their neighbours. By breeding locally early, males increased their chances of becoming polygynous, while females reduced their chances of mating with an already mated male. Our results suggest that secondary females may compensate the fitness costs, if any, of sharing a mate, since their number of descendants did not differ from monogamous females. We emphasize the need of accounting for local breeding settings (ecological, social, spatial, and temporal) and the phenotypic composition of neighbours to understand individual mating decisions.

Long-Term Population Fluctuations of A Burrowing Owl Population On Kirtland Air Force Base, New Mexico, USA

Abstract Western Burrowing Owls (Athene cunicularia hypugaea; hereafter, Burrowing Owls) were once widespread residents of grasslands throughout western North America, but their range has contracted, and abundance has declined in some regions. The causes of declines and geographic variation in population trends of Burrowing Owls are unclear but may be linked to changing land use and urbanization. Burrowing Owls are often found in association with airfields and airports, and their presence at such facilities is sometimes considered to be in conflict with those operations. Documenting the long-term persistence of Burrowing Owls at active airfields can help airfield managers who face decisions regarding compatibility of owls and airfield operations. We report the results of a long-term effort to monitor Burrowing Owls on Kirtland Air Force Base in New Mexico, USA, including the rapid recovery of Burrowing Owl numbers from near-extirpation and the relationships between abundance and other demographic traits. The number of breeding pairs of Burrowing Owls increased from one pair in 2013 to 28 pairs in 2019 and 2020, and the number of fledglings produced increased from one in 2013 to 84 in 2019 and 61 in 2020. The recovery was not uniform across all areas of Kirtland Air Force Base, and some formerly occupied areas remained unoccupied. We documented dispersal outside the Air Force base boundary and that the number of breeding pairs was more strongly influenced by the number of offspring produced in the prior year than the number of owls returning from prior years, which indicated that the population is part of a larger meta-population. Our results demonstrate that the maintenance of Burrowing Owl populations is not necessarily at odds with safe airfield operations, that Burrowing Owls exhibit complex population dynamics, and can rapidly recolonize previously occupied areas if habitat and nest sites remain suitable.

Weather fluctuations are linked to nesting success and renesting decisions in saffron finches

Life‐histories of neotropical birds seem to vary beyond what is expected according to patterns from northern temperate regions. This variation is well exemplified by saffron finches Sicalis flaveola in subtropical Brazil. They breed for five months on a climate that is relatively warm and rainy throughout the year. Females may attempt from one nest with two eggs up to three nests with five eggs per season. Previous work showed that age and individual quality were insufficient to explain variation in their breeding traits. Thus, other factors may still influence reproductive traits of investment and productivity in females. We asked 1) whether breeding traits of individual females were related to temperature and rain from previous weeks, and 2) whether fluctuations in weather during nest phases influenced egg and nestling survival. We monitored 237 nests of 70 marked females for four years. We found that the odds of a female starting a subsequent nest increased when temperatures on the preceding 15–6 weeks were low. Nest success decreased alongside the temperatures before laying dates. The odds of eggs surviving until hatching increased when weather was cold and rainy during incubation. There was no correlation between past weather and laying dates, clutch sizes, egg or nestling masses, incubation periods or number of fledglings per nest. The adverse effects of warmer temperatures and the survival benefit of increased rainfall are surprising and contrary to other birds' patterns. The mechanisms that link weather to renesting probability and nest success in saffron finches are still unknown, and we give some suggestions about their nature. We advocate that further studies with this widespread species might provide further insights into the variability of life‐histories in the region.

Risk‐taking behaviour relates to timing of breeding in a sub‐Antarctic rainforest bird

Within‐population variation in timing of breeding may be linked to a trade‐off between the risks and benefits of breeding earlier. This trade‐off may be mediated by individual risk‐taking behaviour, but this needs to be assessed in detail in wild populations. Here, we recorded timing of breeding and risk‐taking behaviour during three consecutive breeding seasons in a resident population of Thorn‐tailed Rayadito Aphrastura spinicauda located in Navarino Island (55°S), southern Chile. Navarino is a high‐latitude, highly seasonal continental island in southern Chile where early breeding may be risky for rayaditos, given the presence of low temperatures, storms and relatively low food abundance during early spring. We used novel environment tests to assess exploratory behaviour, which in turn was used as a proxy of risk‐taking behaviour. In addition, we evaluated the potential consequences of timing of breeding and risk‐taking behaviour on three measures of reproductive success: clutch size, number of fledglings produced and body condition of the offspring. We found that risk‐prone individuals started breeding earlier than risk‐averse individuals but we did not find evidence for an effect of timing of breeding on any of the variables of seasonal breeding success. However, we observed that fast‐exploring females tended to lay smaller clutches. Measurements reflecting lifetime reproductive success may better reflect an effect of timing of breeding and risk‐taking behaviour, but this needs to be studied. Our results support the idea that risk‐taking behaviour is linked to early breeding in high‐latitude environments. We suggest that, despite the risks that low temperatures and snowstorms pose to breeding rayaditos during early spring, it is possible that early breeders increase the probability of occupying better nesting cavities and they may adjust the timing of breeding to match brood provisioning with peak resource abundance.

Does plumage colour signal fitness in the tawny owl Strix aluco?

Plumage colour has been hypothesized to signal fitness in its component parts survival and reproduction. In the tawny owl Strix aluco, grey individuals have been considered to be more viable and productive than brown ones in cold environmental conditions. The recent increase in the frequency of the brown morph in Finland has been explained by the climate warming. However, in recent decades there have been no trends in the general mildness of winters. Therefore, trends in the abundance of owls due to climate warming per se were unexpected. In a population near the southern coast of Finland, the abundance of grey (not brown) individuals increased significantly during the period 1986–2018, suggesting that natural selection has recently favoured the grey colour morph. During snowy and cold winters grey owls seemed to survive better than brown ones, suggesting that plumage colour signals adaptations to winter weather. The proportion of brown individuals in each year was best explained by the joint effect of snow cover and winter temperature. Extreme peaks in snow fall and cold winters seemed to affect substantially and rather similarly the abundance of both colour morphs. Between population differences in the occurrence of colour morphs were probably due to local and temporal differences in the snow cover. The number of fledglings was significantly related to the colour morph and weather conditions of the preceding winter in males but not in females. This suggests that coloration of males signals fitness in reproduction.

Using long-term data for a reintroduced population to empirically estimate future consequences of inbreeding.

Inbreeding depression is an important long-term threat to reintroduced populations. However, the strength of inbreeding depression is difficult to estimate in wild populations because pedigree data are inevitably incomplete and because good data are needed on survival and reproduction. Predicting future population consequences is especially difficult because this also requires projecting future inbreeding levels and their impacts on long-term population dynamics, which are subject to many uncertainties. We illustrate how such projections can be derived through Bayesian state-space modeling methods based on a 26-year data set for North Island Robins (Petroica longipes) reintroduced to Tiritiri Matangi Island in 1992. We used pedigree data to model increases in the average inbreeding level (F) over time based on kinship of possible breeding pairs and to estimate empirically Ne /N (effective/census population size). We used multiple imputation to model the unknown components of inbreeding coefficients, which allowed us to estimate effects of inbreeding on survival for all 1458 birds in the data set while modeling density dependence and environmental stochasticity. This modeling indicated that inbreeding reduced juvenile survival (1.83 lethal equivalents [SE 0.81]) and may have reduced subsequent adult survival (0.44 lethal equivalents [0.81]) but had no apparent effect on numbers of fledglings produced. Average inbreeding level increased to 0.10 (SE 0.001) as the population grew from 33 (0.3) to 160 (6) individuals over the 25 years, giving a ratio of 0.56 (0.01). Based on a model that also incorporated habitat regeneration, the population was projected to reach a maximum of 331-1144 birds (median 726) in 2130, then to begin a slow decline. Without inbreeding, the population would be expected stabilize at 887-1465 birds (median 1131). Such analysis, therefore, makes it possible to empirically derive the information needed for rational decisions about inbreeding management while accounting for multiple sources of uncertainty.

Identifying the paths of climate effects on population dynamics: dynamic and multilevel structural equation model around the annual cycle

How environmental factors influence population dynamics in long-distance migrants is complicated by the spatiotemporal diversity of the environment the individuals experience during the annual cycle. The effects of weather on several different aspects of life history have been well studied, but a better understanding is needed on how weather affects population dynamics through the different associated traits. We utilise 77 years of data from pied flycatcher (Ficedula hypoleuca), to identify the most relevant climate signals associated with population growth rate. The strongest signals on population growth were observed from climate during periods when the birds were not present in the focal location. The population decline was associated with increasing precipitation in the African non-breeding quarters in the autumn (near the arrival of migrants) and with increasing winter temperature along the migration route (before migration). The number of fledglings was associated positively with increasing winter temperature in non-breeding area and negatively with increasing winter temperature in Europe. These possible carry-over effects did not arise via timing of breeding or clutch size but the exact mechanism remains to be revealed in future studies. High population density and low fledgling production were the intrinsic factors reducing the breeding population. We conclude that weather during all seasons has the potential to affect the reproductive success or population growth rate of this species. Our results show how weather can influence the population dynamics of a migratory species through multiple pathways, even at times of the annual cycle when the birds are in a different location than the climate signal.

Breeding biology of the Eleonora’s falcon, Falco eleonorae within the Galite archipelago

This study was carried out at Galite archipelago over two consecutive breeding seasons (2014 and 2015). We investigated the breeding ecology of Eleonora’s falcon population in Galite archipelago by providing detailed data on its breeding biology and assessing the nesting parameters. Overall, 127 Eleonora’s falcon breeding pairs were recorded in all six islets of the archipelago. The eastern part of the archipelago hosted the highest number of breeding pairs with the highest density recorded at Gallo island (5.93 pairs/ha). Eleonora’s falcon breeding pairs mainly used the protected crevices non-exposed to sun and wind. The overall mean clutch size (mean ± SE) was 1.78 ± 0.10 eggs per clutch. Clutches of two eggs and one egg were the most frequent at Gallo and Fauchelle, respectively. The average hatched eggs per clutch and fledglings per brood were 1.29 ± 0.10 and 1.24 ± 0.10, respectively. The brood size varied significantly with clutch size and nest exposition being higher related to not exposed nest and two as the clutch category was greater. Likewise, the number of fledglings significantly increased with increasing clutch category and was higher in not exposed nests. In fact, hatching or fledging probability increased significantly as nests were not exposed.