Lesser Kestrel Falco Naumanni Research Articles

Itinerant lifestyle and congregation of lesser kestrels in West Africa

Trans‐Saharan migrants often spend a large proportion of their annual cycle wintering in the Sahel. Advances in fieldwork and tracking technology have greatly enhanced our ability to study their ecology in these areas. Using GPS‐tracking we aimed to investigate the little known non‐breeding movements of the lesser kestrel Falco naumanni in sub‐Saharan Africa. We segment non‐breeding tracks (n = 79 tracks by 54 individuals) into staging events (131 ± 25 days per non‐breeding cycle), itinerant movements between staging sites (11 ± 10 days), and non‐directed exploratory movements (6 ± 5 days). We then describe timing and directionality of itinerant movements by male and female kestrels throughout the non‐breeding season. Regardless of sex, lesser kestrels spent on average 89% of the non‐breeding season staging at two (range = 1–4) sites in West Africa. At the end of September, kestrels arrived along a broad front throughout the northern Sahel. By December, however, they congregated into two distinct clusters in Senegal and along the Malian–Mauritanian border. The birds stayed for longer periods and showed greater daily activity in the latter areas, compared to their first and intermediate ones. Among 24 individuals tracked along multiple annual cycles, 20 individuals consistently used the Senegalese or Malian–Mauritanian cluster. The remaining four birds either used these clusters in the 2nd or 3rd year of tracking or alternated between them across different years. The eastward and westward itinerant movements of lesser kestrels during the non‐breeding season, coupled with their tendency to cluster geographically towards the end, differ from the southward movements of other insectivorous raptors in West Africa. While 31% of Spanish lesser kestrels converged in Senegal, where roosts of > 20 000 birds are known, 68% moved into the Malian‐Mauritanian border region where more groundwork is needed.

Lesser kestrels of the same colony do not overwinter together

Abstract Migratory connectivity describes the linkage between breeding and nonbreeding sites, having major ecological implications in birds: 1 season influence the success of an individual or a population in the following season. Most studies on migratory connectivity have used large-scale approaches, often considering regional populations, but fine-scale studies are also necessary to understand colony connectivity. The lesser kestrel Falco naumanni, an insectivorous migratory raptor which form colonies during the breeding period, was considered to have strong connectivity based on regional populations. However, no small-scale studies on migratory connectivity have been conducted. Therefore, we GPS (Global Positioning System)-tracked 40 adult lesser kestrels from 15 different Spanish breeding colonies, estimating the overlap index between home ranges and the distance between their centroids. It was found that lesser kestrels from the same breeding colony placed their nonbreeding areas at 347 ± 281 km (mean ± standard deviation) away from each other (range = 23–990), and their home ranges overlapped by 38.4 ± 23.6%. No differences between intra-colony and inter-colony metrics were found, which suggests that lesser kestrels from the same breeding cluster do not overwinter together, but they spread out and mixed independently of the colony belonging throughout the nonbreeding range of the species. Ultimately, this study highlights the importance of performing connectivity studies using fine-scale approaches.

Within‐colony segregation of foraging areas: from patterns to processes

Spatial segregation of foraging areas among conspecifics breeding in neighbouring colonies has been observed in several colonial vertebrates and is assumed to originate from competition and information use. Segregation between foraging individuals breeding in different parts of a same colony has comparatively received limited attention, even though it may have strong impacts on colony structure and individual fitness, and thus on population dynamics of colonial species. To shed light on the processes (namely competition and memory) driving small‐scale spatial segregation of foraging areas in colonial species, we used empirical data and developed an individual based model (IBM). By GPS tracking lesser kestrels Falco naumanni breeding in an urban area and foraging in the surrounding farmland, we found that foraging areas of individuals nesting in two close‐by (ca 600 m) roof terraces (i.e. nest clusters) were significantly spatially segregated. Individuals from different nest clusters showed different departure bearings and encountered different habitats but showed similar fitness traits. Individuals from the same cluster did not seem to follow conspecifics when leaving for a foraging trip. The IBM, based on data from seven roof terraces, showed that such collective spatial segregation does not necessitate social information use: personal information and memory may be sufficient to mechanistically explain intra‐colony segregation of foraging areas. Besides, there was a clear distance‐dependent segregation: individuals from distant clusters segregated more, matching what is observed at large spatial scales (i.e. among neighbouring colonies). Our results do not question the fact that colonial species may use social information during foraging or that colonies can act as information centres. Instead, they suggest that within‐colony foraging range spatial segregation, arising from simple mechanisms not necessarily involving information sharing, might be widespread in colonial systems. These results thus further challenge the long‐standing view that colonies should be regarded as single cohesive entities.

The occurrence of a flagship raptor species in intensive agroecosystems is associated with more diverse farmland bird communities: Opportunities for market-based conservation

Traditional livestock systems have supported farmland biodiversity for millennia. However, modern intensive husbandry is challenging wildlife persistence in agroecosystems. We assessed the multiscale determinants of the species richness of breeding bird communities, as well as the occurrence of a flagship raptor species, the lesser kestrel Falco naumanni, in an intensive agroecosystem mostly dedicated to the production of the world-renowned Parmigiano Reggiano cheese. We relied on three avian community richness metrics reflecting a gradient of increasing association with farmed landscapes, i.e. the overall breeding bird species richness, the richness of farmland species, and the richness of ground-nesters (i.e. species that mostly breed within crops) and tested their association with the landscape, agricultural, and pedological variables as well as with lesser kestrel occurrence. We showed that environmental variables determining overall richer avian assemblages did not coincide with those shaping farmland and ground-nesting species richness, thus challenging the potential effectiveness of conservation actions. However, such actions could be optimized by taking into account different spatial scales affecting different species groups. Indeed, landscape heterogeneity, semi-natural/marginal habitats, and a moderate cover of build-up areas enhanced overall species richness at a small spatial scale. At a broader scale, landscape heterogeneity enhanced farmland species richness, whereas fragmentation determined by urbanization negatively affected ground-nesters. Avian community richness metrics were maximized at an intermediate cover of three prevailing crops (winter, summer, and hay crops), increasing when they co-occurred, i.e., in the presence of crop rotation. Lesser kestrel occurrence was associated with richer assemblages of ground-nesting species because this raptor and ground-nesters showed analogous ecological requirements. These findings suggest that the lesser kestrel can be regarded as an ideal flagship for market-based conservation initiatives (e.g., tailored to the production of biodiversity-friendly agri-food products) in intensive agroecosystems since actions aimed at improving the foraging habitats of the species are likely to benefit co-occurring farmland birds of conservation interest.

A first insight into the post-breeding dispersal strategies of adult Lesser Kestrels Falco naumanni in Italy

ABSTRACT Capsule After breeding, Lesser Kestrels Falco naumanni do not migrate directly to Africa but exhibit a post-breeding dispersal that lasts several weeks. Tracking of four adult individuals provides the first data on distances and direction of travel, and suggests sex differences in post-breeding dispersal. Aims We aimed to: (a) detect the dispersal routes and stopover sites used by adult Lesser Kestrels during the post-breeding period in Italy, (b) deduce the strategies behind the observed dispersal behaviour, and (c) advance hypotheses about the determinants of such strategies. Methods Using Argos satellite telemetry, we tracked four individuals at neighbouring urban colonies at Gravina and Altamura (Apulia region), within the geographical area (Alta Murgia) which has the world’s highest known density of urban nesting Lesser Kestrels. Results Argos devices provided 4930 high-quality locations for 72 ± 13 (mean ± SD) days for four individuals tracked during July–September. July corresponded to the post-nestling period, with recorded dispersal distances less than 66 km from the breeding site. At the beginning of August, the birds entered the pre-migration period, with recorded dispersal distances up to 667 km from the colony. We detected four dispersal strategies: absolute fidelity to the breeding site, and short-range, mid-range, and long-range dispersal. The males had long-range and mid-range dispersal routes parallel to the eastern side of the Apennine ridge, and selected several stopover sites in central and northern Italy. The females showed absolute fidelity to the breeding site and short-range dispersal. We hypothesize that males and females had different body conditions at the beginning of the pre-migration period, which forced females to remain close to the breeding site while males could disperse further. Conclusions This work sheds light, for the first time, on the post-reproductive dispersal behaviour and schedule of the Lesser Kestrel in Italy.

Overlap and Segregation among Multiple 3D Home Ranges: A Non-Pairwise Metric with Demonstrative Application to the Lesser Kestrel Falco naumanni.

In this study we solved the issue of measuring the degree of overlap/segregation among an arbitrarily large number (n ≥ 2) of 3D volumetric home ranges (i.e., x, y, and hg; where hg is height above ground level) for the first time. For this purpose, we introduced the novel non-pairwise index MVOI (Multiple Volumetric Overlap Index) and its complement to 100 MVSI (Multiple Volumetric Segregation Index). Regardless of the number of 3D volumetric home ranges, the MVOI and MVSI generate a single score of overlap/segregation between 0 and 100, making ecological interpretation much easier and more meaningful when compared to n × n pairwise overlap indices. As a case study, we applied the MVOI and MVSI to 12,081 GPS points of five lesser kestrels (Falco naumanni) during the nesting period at Santeramo in Colle (Apulia region; Italy) in an area with the most elevated density of lesser kestrels in urban colonies worldwide. The 3D volumetric home ranges ranged between 1.79 km3 and 8.19 km3. We found that the tracked birds had different vertical profiles, possibly to limit intraspecific competition, resulting in a 3D home range overlap that was only 61.1% of the 2D overlap and 52.8% of the probabilistic one.

Causes of the recent decline of a Lesser Kestrel (Falco naumanni) population under an enhanced conservation scenario

Lesser Kestrel Falco naumanni (Fleischer, 1818) populations have been one of the best monitored bird populations in Spain over the last 70 years. These populations suffered a sharp decline between the 1950s and 1990s. Since then, periodic censuses showed a population increase that lasted until the 2010s. In those years, numerous projects for the recovery of the species were also initiated (some EU LIFE Projects, among others), which have continued to the present day. However, despite conservation efforts, the Spanish Lesser Kestrel population, which includes about 40% of the European breeding population, has declined at a rate of 6% per year since 2012. In this study, we analysed changes in habitat and population size in 12 colonies located in La Mancha between 2003 and 2021 in order to identify possible causes of the current decline. This colonial species breeds in old buildings, and roof area (a proxy for house size) was the predictor that best accounted for the number of pairs in a colony in a given year. In addition, the extent of herbaceous crops (related to prey availability) explained a similar amount of colony size variance in 2021, whereas in 2003, the availability of large Orthoptera itself had a significant effect but a much lower effect size. The number of nestboxes affected positively the number of breeding pairs in 2021 but explained only 1% of the variance. The decline of the Lesser Kestrel population between 2003 and 2021 was largely explained by the decrease of the density of large orthopterans, their main prey. The model with the minimum Akaike Information criterion adjusted for small sample size (AICc) value also included a positive association with changes in roof area and a negative association with rabbit density (possibly through a hyperpredation phenomenon). Other top models (i.e. ΔAICc ≤ 2 units) also showed negative effects of the loss of favourable land uses (pasture lands and herbaceous crops) on colony size, probably because this caused a reduction in the availability of large Orthoptera. These changes in land use occurred less often in areas protected by the Natura 2000 network, which may thus have contributed to the conservation of the Lesser Kestrel population. However, other conservation measures such as the installation of nestboxes were not as efficient as expected.

Windfarm collisions in medium‐sized raptors: even increasing populations can suffer strong demographic impacts

AbstractThe impact of bird mortality by collision on windfarms has often been evaluated at the individual level, but rarely at the population level. The Lesser kestrel Falco naumanni is an endangered short‐lived migratory raptor, susceptible to collision with wind turbines. We evaluated the impacts of windfarm turbine collisions on the demography of the largest lesser kestrel population in France. Using data from local monitoring of reproduction and windfarm mortality surveys, combined with capture‐recapture ringing data at a nearby population, we quantified vital parameters of fecundity and survival in order to parameterize a matrix population model to study the viability of this population. The breeding success was high and varied in synchrony with survival probabilities. Between 2013 and 2020, 43 carcasses were found below wind turbines, and when accounting for carcass detection and persistence rates, the true mortality should approach 154 individuals in that period, i.e. 3% of the studied population was affected by collisions each year. The matrix model showed that the population growth observed was only possible if there was a constant recruitment of 26 immigrant individuals each year into the population. Without the excess mortality by the windfarm, we predict that this population would have 22% more breeding pairs than what was observed in 2020. Simulations over 30 years showed that, under the current immigration rate, the population should decline if the excess mortality exceeds 11%. If immigration ceases, the population would decline above 5% excess mortality per year. It is urgent to monitor and reduce the excess mortality by windfarm collisions that threatens this lesser kestrel population. More generally, we advocate the use of population matrix demographic models in impact assessment studies to avoid placing new windfarms close to rare species that could not sustain additional mortality by collisions.

Extra food provisioning does not affect behavioral lateralization in nestling lesser kestrels.

Costs and benefits of brain lateralization may depend on environmental conditions. Growing evidence indicates that the development of brain functional asymmetries is adaptively shaped by the environmental conditions experienced during early life. Food availability early in life could act as a proxy of the environmental conditions encountered during adulthood, but its potential modulatory effect on lateralization has received little attention. We increased food supply from egg laying to early nestling rearing in a wild population of lesser kestrels Falco naumanni, a sexually dimorphic raptor, and quantified the lateralization of preening behavior (head turning direction). As more lateralized individuals may perform better in highly competitive contexts, we expected that extra food provisioning, by reducing the level of intra-brood competition for food, would reduce the strength of lateralization. We found that extra food provisioning improved nestling growth, but it did not significantly affect the strength or direction of nestling lateralization. In addition, maternal body condition did not explain variation in nestling lateralization. Independently of extra food provisioning, the direction of lateralization differed between the sexes, with female nestlings turning more often toward their right. Our findings indicate that early food availability does not modulate behavioral lateralization in a motor task, suggesting limited phenotypic plasticity in this trait.

High trophic niche overlap in mixed‐species colonies using artificial nests

Although successful at recovering endangered populations, conservation actions based on nest provisioning seldom consider how they shape the composition of communities and alter interspecific interactions. Specifically, the extent to which dietary overlap within these communities may affect the conservation of target species has rarely been assessed. In Southern Europe, sites of large‐scale nest‐site provisioning aimed at recovering Lesser Kestrels Falco naumanni populations have attracted non‐target bird species, resulting in mixed breeding assemblages that might promote interspecific competition for resources during breeding. Here we used stable isotope analysis (δ15N and δ13C) to assess inter‐ and intraspecific dietary segregation in these assemblages and investigate the mechanisms allowing species coexistence. We examined resource partitioning and trophic niche overlap among Lesser Kestrels, Common Kestrels Falco tinnunculus, European Rollers Coracias garrulus, Western Barn Owls Tyto alba, Little Owls Athene noctua and Spotless Starlings Sturnus unicolor; and within species between parents and their offspring. Similar isotope ratios and highly overlapped niches, particularly among Lesser Kestrels, Rollers and Starlings, suggest limited dietary segregation and use of similar prey. Within species, parent–offspring segregation was marked across all species. Our results indicate that species breeding in these assemblages occupy similar ecological niches, despite a potential increase in competition. High resource availability in the area may permit coexistence but the viability of mixed‐species groups may be compromised in areas with limited resources, which are predicted to expand with ongoing human‐ and climate‐induced changes. Conservation practices based on nest provisioning should consider the ecological niches of target and non‐target species as well as their interactions.

Measuring the Degree of Overlap and Segregation among Multiple Probabilistic Home Ranges: A New Index with Illustrative Application to the Lesser Kestrel Falco naumanni.

Simple SummaryIntraspecific and interspecific interactions regulate the extent and spatial patterns of animal home ranges. If we are able to estimate the home range overlap for a large number of individuals, populations and/or species, then we can readily identify important ecological properties, such as social network structure, competition during the breeding season, contact rates with implications for disease transmission, change in space use over time, interactions among different age classes and site fidelity for a particular individual, population or species. We can also evaluate the robustness of probabilistic home range assessment through the degree of overlap of several estimators. Accordingly, in this study, we first solve the issue of measuring the degree of overlap/segregation among a large number of probabilistic animal home ranges and provide a demonstrative case study.Home range overlap/segregation has several important applications to wildlife conservation and management. In this work, we first address the issue of measuring the degree of overlap/segregation among an arbitrarily large number (i.e., n ≥ 2) of probabilistic animal home ranges (i.e., utilization distributions). This subject matter has recently been solved for home ranges measured as polygons (e.g., percent minimum convex polygons and multinuclear cores) but not yet for probabilistic ones. Accordingly, we introduce a novel index named the PGOI (probabilistic general overlap index), and its complement, the PGSI (probabilistic general segregation index), an index for computation of probabilistic home range overlap/segregation at individual, population and species levels. Whatever the number of probabilistic home ranges, the PGOI returns a single score ranging in the [0, 100] interval. We applied the PGOI to five lesser kestrels (Falco naumanni) at Santeramo in Colle (Apulia region; Southern Italy) as a case study. Our new index can be applied to any animal species and to home ranges derived from any type of probabilistic home range estimator.

Foraging Habitat Selection by the Lesser Kestrel Falco naumanni During the Different Phases of Breeding and the Post Breeding Period in Central Greece

The purpose of this study was to evaluate the selection of foraging habitats by the Lesser Kestrel Falco naumanni during the different phases of breeding and the post breeding season on the Plain of Thessaly, central Greece. Foraging habitat selection by the species was recorded by direct visual observation in 2014 and 2015 during their presence in the area. Habitat selection was analyzed using the Savage selectivity index. The results indicate that Lesser Kestrels were likely to positively select fallow and set-aside land from pair formation to the pre-migratory phase, but with some annual variation. Legumes (Alfalfa) and cereals were also positively-selected crop categories, whereas cotton and other kinds of cultivation were significantly avoided. During the incubation and chick rearing phase, cereals (the most widespread form of cultivation in the area), were positively selected, which highlights the importance of these crops during this critical breeding phase. Prey abundance and availability, which depend on farming practices, seem to be the main reasons for the periodic variation in the species' habitat selection in the area.

Barrier crossings and winds shape daily travel schedules and speeds of a flight generalist

External factors such as geography and weather strongly affect bird migration influencing daily travel schedules and flight speeds. For strictly thermal-soaring migrants, weather explains most seasonal and regional differences in speed. Flight generalists, which alternate between soaring and flapping flight, are expected to be less dependent on weather, and daily travel schedules are likely to be strongly influenced by geography and internal factors such as sex. We GPS-tracked the migration of 70 lesser kestrels (Falco naumanni) to estimate the relative importance of external factors (wind, geography), internal factors (sex) and season, and the extent to which they explain variation in travel speed, distance, and duration. Our results show that geography and tailwind are important factors in explaining variation in daily travel schedules and speeds. We found that wind explained most of the seasonal differences in travel speed. In both seasons, lesser kestrels sprinted across ecological barriers and frequently migrated during the day and night. Conversely, they travelled at a slower pace and mainly during the day over non-barriers. Our results highlighted that external factors far outweighed internal factors and season in explaining variation in migratory behaviour of a flight generalist, despite its ability to switch between flight modes.

Assessing the relative importance of managed crops and semi-natural grasslands as foraging habitats for breeding lesser kestrels Falco naumanni in southeastern Italy

Farmland habitats host important populations of several threatened bird species. So far, how to reconcile farmland management with the maintenance of viable populations of these taxa is a major challenge for conservation biology. Southeastern Italy hosts ca 7000 pairs of breeding lesser kestrels Falco naumanni, representing one of the European strongholds of this small colonial raptor of conservation concern. We firstly assessed the relative importance of managed crops versus semi-natural grasslands in determining the local abundance of lesser kestrels at the landscape scale, and we successively studied the foraging habitat preferences at a smaller spatial scale. Surveys of foraging birds were associated with land-use collection at 191 homogeneous habitat sampling parcels from 14 plots of 16 km2 each, uniformly distributed over a 2400 km2 area. Each plot was visited six times during the 2017 breeding season (May–July). Land-use markedly changed along the season, unripe cereals being dominant in May, while harvested cereal crops prevailed in July. Land-use did not affect lesser kestrel distribution early in the season while foraging birds were more abundant in plots with a greater proportion of harvested cereal crops and a lower one of semi-natural grassland in the late breeding season. In accordance, the analysis of foraging habitat preferences within plots showed that in May unripe cereal crops and semi-natural grasslands were used proportionally to their availability. In June and July, harvested cereal crops were used more than expected from their availability, while semi-natural grasslands were significantly avoided. Our landscape-scale analysis thus indicates that semi-natural grasslands are much less used in comparison to harvested crops during the mid and late parts of the breeding season, suggesting that lesser kestrel may be able to take advantage of crop management practices more than other farmland birds of conservation priority.

Carryover effects of long-distance avian migration are weaker than effects of breeding environment in a partially migratory bird

Migration may expose individuals to a wide range of increasing anthropogenic threats. In addition to direct mortality effects, this exposure may influence post-migratory reproductive fitness. Partial migration—where a population comprises migrants and residents—represents a powerful opportunity to explore carryover effects of migration. Studies of partial migration in birds typically examine short-distance systems; here we studied an unusual system where residents breed in mixed colonies alongside long-distance trans-Saharan migrants (lesser kestrels (Falco naumanni) in Spain). Combining geolocator data, stable isotope analysis and resighting data, we examined the effects of this stark difference in migratory strategy on body condition, breeding phenology and breeding success. We monitored four colonies in two regions of southern Spain for five consecutive years (2014–2018), yielding 1962 captures, determining migratory strategy for 141 adult bird-years. Despite a 3000-km difference in distance travelled, we find no effect of strategy on breeding parameters. We find weak evidence for a short-term negative carryover effect of migration on body condition, but this was only apparent in the breeding region with lower primary productivity. Our results indicate that carryover effects of even highly divergent migratory strategies may be minimal relative to effects of conditions experienced on breeding grounds.

A new general index of home range overlap and segregation: the Lesser Kestrel in Southern Italy as a case study

BackgroundThere is increasing interest in evaluating home-range overlap (or, otherwise, segregation) between bird species, and between or within bird populations, to inform spatial planning. So far, studies of home-range overlap typically make use of comparisons between pairs of individuals, populations or species, and return a matrix of pairwise overlaps (e.g., percent overlaps). However, when the number of individuals, populations or species to be compared is elevated, an overlarge overlap matrix is difficult to interpret from an ecological viewpoint.MethodsWe propose here a new, conceptually simple and computationally efficient index (general overlap index; GOI) for the ready computation within GIS of home range overlap of an arbitrarily large number (i.e., n ≥ 2) of individuals, populations or species. Whatever the number of home ranges to be compared, GOI always returns a single score between 0 and 100. As a case study, we applied our index to 24,074 GPS points of 10 Lesser Kestrels (Falco naumanni) in order to estimate within-colony and between-colony overlaps in two neighboring colonies in Southern Italy.ResultsWithin-colony overlap was elevated for both colonies (96.41% at Cassano delle Murge, n = 5 individuals; 81.38% at Santeramo in Colle, n = 5 individuals), while between-colony overlap was low (19.12%; n = 2 colonies) and, after a randomization procedure, more spatially-segregated than expected by chance.ConclusionsModern biotelemetry offers huge amounts of data describing the space use of animal species. The use of intuitive and straightforward indices, like GOI, can be useful to promptly extract ecological information from such an amount of data (e.g. detecting change in space use over successive years, evaluating the reliability of various home-range estimators).

Extra food provisioning reduces extra‐pair paternity in the lesser kestrel Falco naumanni

Female promiscuity can function to acquire both direct and indirect benefits from their social mate and extra‐pair males. In many raptor species, intense mate‐feeding significantly contributes to female energy requirements before and during egg laying. Moreover, females may use mate‐feeding effort to assess male quality. In this study of the lesser kestrel Falco naumanni, we aimed at experimentally manipulating the female's perception of mate quality by providing females with extra food during egg laying, and evaluated the occurrence of extra‐pair paternity in food‐supplemented and control broods by parentage analyses. No extra‐pair offspring (EPO) was found among 19 food‐supplemented broods, whereas EPO occurred in five out of 17 control broods. No significant differences in morphological traits, body condition and reproductive success were found between faithful and unfaithful females. However, clutches containing EPO were laid later in the breeding season. Moreover, un‐cuckolded males had longer tarsi than cuckolded ones, indicating larger body size. Hence, extra food provisioning and early breeding reduced the occurrence of EPO in lesser kestrels. In addition, we confirmed the occurrence of intraspecific brood parasitism, as five nestlings were not the offspring of the brooding female. The results of our food‐provisioning experiment support the idea that mate‐feeding ability is a reliable indicator of male quality, and are in accordance with the hypothesis that male mate‐feeding behaviour is a sexually selected trait.

Sibling competition affects body condition and allostatic load in the colonial nesting lesser kestrel Falco naumanni

Sibling competition leading to physiological stress and elevated allostatic load is driven by asymmetrical development and limited resources. To investigate these predictions, we studied broods of the lesser kestrel Falco naumanni, from a nest-box population in Armenio, Central Greece. For each nestling reared in nest-boxes, we noted the age (in days) since hatching, measured the wing chord length and body mass. We also clipped the central right rectrix for ptilochronology for subsequent analysis in the laboratory. We measured 206 nestlings from 61 broods (range 2-5 nestlings). In the case of nestlings < 18 days old (n = 198, 96.1% of all) we also measured the length of feathers. As a measure of body condition, we used the residuals of the linear regression for the relationship between wing chord length and body mass, while the growth bar width of feathers was used as a second, independent index of body size and allostatic load. A GLMM and information-theory criterion showed that both measures of body condition decreased incrementally from the first sibling to the most subordinate in the brood. Body condition of subordinate siblings was influenced by the number of siblings in the nest; i.e. the larger the brood size the greater the discrepancy in body condition between siblings. At the same time, we did not find any influence of sex on either measure of fitness. Thus, our results indirectly support the hypothesis that sibling competition may cause physiological developmental stress which is reflected in decreased body condition and increased allostatic load for younger nestlings.

Long-term persistence of conservation-reliant species: Challenges and opportunities

“Conservation-reliant species” – those fully dependent on continued management actions – are booming and, with limited conservation budgets, securing funds to sustain their long-term viability is becoming overwhelming. This study assesses the degree of dependence on conservation actions of two obligatory cavity-nesters, the Lesser Kestrel Falco naumanni and the European Roller Coracias garrulus, whose populations in Europe were recently recovered through artificial nest-site provisioning. Using long-term monitoring data and population surveys conducted in their main Portuguese stronghold, we examined temporal changes in the availability and use of semi-natural (cavities in rural abandoned buildings) and artificial nest-sites. We further assessed the financial costs of nest-site provisioning and evaluated the potential use of tourism revenues as a conservation funding source. Following the implementation of conservation projects, the Lesser Kestrel and Roller populations have been increasing but >65% of all breeding pairs currently nest in artificial nest-sites. Semi-natural nest-sites remain suitable for approximately 30 years and are expected to disappear by the end of this century. Lesser Kestrels and Rollers will thus become fully dependent on artificial nest-sites and sustaining their current population sizes is estimated to cost 4500€ per year. This represents <1% of the region's lodging income, largely supported by nature-based tourism. Our findings suggest that reactive conservation measures can be very effective at recovering endangered populations but can make them fully reliant on the perpetuation of those measures. This demands long-term funding, which can be alleviated by tourism revenues in areas with high nature capital values.

The Breeding Success of Lesser Kestrels Falco naumanni in Mongolia

We examined the breeding success of Lesser Kestrels Falco naumanni in Ikh Nart Nature Reserve, a semi-desert zone in southeast Mongolian. We found that the mean number of nests per colony was 7.4. Lesser Kestrels laid eggs between 24 May and 2 June each year. Mean clutch size was 4.0±0.7 SE, with a mean incubation period of 28±2 SE days. We recorded an overall hatching success rate of 84.2% and overall fledgling success rate of 89.7%, hence a mean fledgling per breeding attempt was 2.79. Our findings revealed relatively high hatching and fledgling rates for our study population, and bode well for the conservation of this small falcon in its poorly-known breeding range.