Agricultural intensification is one of the main threats to biodiversity. Farmland bird specialists such as Montagu's harrier, Circus pygargus, are particularly at risk and declining. Conventional ...farming (CF) production systems usually involve landscape homogenisation, mechanisation, and the use of synthetic pesticides that may have direct and indirect effects on individuals. By contrast, organic farming (OF) systems typically promote agroecosystem health, which benefits biodiversity and the reproductive success of birds. However, the potential effects of agricultural systems on life history traits of Montagu's harrier chicks have not been investigated. Still, altered life history traits could impair chick survival and future reproductive success, which may in turn impact population dynamics. Here, we investigated the effects of OF (measured as a percentage around nests at different buffer sizes from 100 m to 2000 m) on a set of life history traits covering the behaviour, physiology (haematological, immune and nervous systems) and body condition of 380 chicks from 137 nests monitored between 2016 and 2021. At a local scale (<2000 m), only the H/L ratio (indicative of physiological stress) and carotenoidbased ornaments were clearly related to OF percentage. At 600 m around the nest, a higher OF percentage increased the H/L ratio, suggesting that chicks experienced greater stress due to either increased human disturbance or higher intra-/interspecific negative interactions around OF crop plots. Carotenoid-based ornaments were more strongly coloured with increasing OF around the nest at 1500 m. Considering the role of carotenoids in both detoxification processes and expression of secondary sexual traits, this result may indicate that CF would lead either to a difference in nestlings' diet and/or to a trade-off between organism's maintenance and sexual characters. These findings suggest that farming practices at a local scale surrounding nest locations may have subtle effects on chick development, but also on trade-offs between important physiological functions. This study highlights the importance of a multi-trait approach when assessing adverse and beneficial effects of both OF and CF on individuals.
Time budgets are a powerful but hitherto seldom used way to study how migrants organise their bi‐annual travels. We studied daily time budgets of travelling Montagu's harriers Circus pygargus, based ...on GPS tracking data, in which we were particularly interested in how time budgets differ between regions and seasons, and are affected by wind. We found that Montagu's harriers used a relatively broad daily time window for travelling by starting daily travels just after sunrise and ending daily travels just before sunset. Occasionally, flights were extended into the night. Montagu's harriers frequently interrupted their daily flights for on average 1.5 h d–1. These interruptions occurred in all regions and seasons. The tracking data during interruptions suggested two different behaviours: in 41% of all interruptions the birds were moving (presumed foraging,) and in 32% they were stationary (presumed resting; the remaining interruptions could not be classified). The interruptions for foraging indicate that Montagu's harriers have a fly‐and‐forage migration strategy (i.e. combine travelling and foraging on the same day), but the interruptions for resting illustrate that their travels comprise of more than fly‐and‐forage behaviour alone. The large number of interruptions for foraging in the Sahara Desert indicates that this region is less hostile for a migrating raptor than presumed previously. Importantly, harriers spent more time on interruptions for resting on days with stronger headwinds, suggesting that interruptions for resting serve a function of waiting for more favourable weather conditions. Daily variation in time budgets was largely explained by wind; harriers flew more hours per day, and interrupted their flights fewer hours per day, on days they experienced stronger tailwinds. In contrast, time budgets were similar between regions and seasons, suggesting that wind rather than landscape and season shape travel routines of Montagu's harriers.
1. Hundreds of millions of Afro-Palaearctic migrants winter in the Sahel, a semi-arid belt south of the Sahara desert, where they experience deteriorating ecological conditions during their ...overwintering stay and have to prepare for spring migration when conditions are worst. This well-known phenomenon was first described by R.E. Moreau and is known ever since as Moreau's Paradox. However, empirical evidence of the deteriorating seasonal ecological conditions is limited and little is known on how birds respond. 2. Montagu's Harriers Circus pygargus spend 6 months of the year in their wintering areas in the Sahel. Within the wintering season, birds move gradually to the south, visiting several distinct sites to which they are site-faithful in consecutive years. At the last wintering site, birds find themselves at the southern edge of the Sahelian zone and have no other options than facing deteriorating conditions. 3. We tracked 36 Montagu's Harriers with GPS trackers to study their habitat use and behaviour during winter and collected data on the abundance of their main prey, grasshoppers, in Senegal. Since grasshopper abundance was positively related to vegetation greenness (measured as normalized difference vegetation index, NDVI), we used NDVI values as a proxy for prey abundance in areas where no field data were collected. Prey abundance (grasshopper counts and vegetation greenness) at wintering sites of Montagu's Harriers decreased during the wintering period. 4. Montagu's Harriers responded to decreasing food availability by increasing their flight time during the second half of the winter. Individuals increased flight time more in areas with stronger declines in NDVI values, suggesting that lower food abundance required more intense foraging to achieve energy requirements. The apparent consequence was that Montagu's Harriers departed later in spring when their final wintering site had lower NDVI values and presumably lower food abundance and consequently arrived later at their breeding site. 5. Our results confirmed the suggestions Moreau made 40 years ago: the late wintering period might be a bottleneck during the annual cycle with possible carry-over effects to the breeding season. Ongoing climate change with less rainfall in the Sahel region paired with increased human pressure on natural and agricultural habitats resulting in degradation and desertification is likely to make this period more demanding, which may negatively impact populations of migratory birds using the Sahel.
The last century has seen a steep decline in biodiversity, and anthropization is considered one of the major drivers of this decline. Anthropogenic disturbances, due to human presence and/or ...activities, may be perceived as chronic stressors by wildlife and potentially lead to deleterious effects on traits related to fitness. The main objective of the present study was to highlight the effects of these anthropogenic elements on wild birds on sparsely urbanized farmland, far less studied than in urbanized areas. We investigated during four successive breeding seasons whether the anthropization level, assessed by infrastructure density around nests, and the harvesting conditions around nests may impact physiological, behavioural and life‐history traits of Montagu's harrier Circus pygargus chicks. Higher anthropization levels were associated with higher basal corticosterone levels in nestlings during only one breeding season and a lower body condition at fledging for females, probably because they suffered from higher starvation than males. Nestlings reared in more anthropized areas or in harvested crops before their fledging harboured more fault bars on rectrices than those reared in less anthropized areas or in unharvested crops regardless of year and sex, which is suggestive of higher stress during development. Nestling behaviours were also impacted by anthropization level and harvesting conditions: chicks in harvested crops were more aggressive and in areas with higher anthropization levels more prone to escape than others. Because Montagu's harrier is a protected species, the impacts highlighted in the present study are a matter of concern, especially regarding farmland landscape modifications, and we advise limiting perturbations in areas where Montagu's harriers usually nest.
We investigated during four successive breeding seasons whether the anthropization level, assessed by infrastructure density around nests, and the harvesting conditions around nests may impact physiological, behavioural and life‐history traits of Montagu's harrier Circus pygargus chicks. We found that chicks may be impacted by human disturbance even if the level of perturbation within the environment is low.
Palearctic migrants wintering in Africa commonly use several sites throughout the winter, a strategy known as ‘itinerancy’. In this way, migrants track spatiotemporal variation in resources. Despite ...the importance of this strategy for migratory landbirds, we still lack detailed understanding of how variation in environmental conditions affects site use and the timing of movements between sites. We tracked 125 adult Montagu’s Harriers Circus pygargus from Western European breeding populations between 2005 and 2018 using satellite transmitters and GPS trackers. In total, data on 129 complete wintering seasons were obtained, including 33 individuals that were followed in two or more winters. Montagu’s Harriers were itinerant, using on average 3.3 wintering sites, to which they showed high site fidelity between years. The first sites harriers used after arriving in their wintering range were situated in the northern Sahel and were dominated by natural and sparse vegetation. Subsequent sites, situated further south in the Sahel, were mainly dominated by agricultural and natural habitats. Sites used by harriers had higher habitat diversity compared to random sites. Home range size and activity (time flying per day, daily distance) peaked at the last sites harriers used (i.e. the site from which they commenced spring migration). For individuals tracked in multiple seasons, we showed that home range size did not depend on vegetation greenness. However, the birds covered longer daily distances at the same site in drier years compared to greener (wetter) years. Importantly, the timing of the movements between wintering sites was affected by local environmental conditions, with individuals staying for shorter durations and departing earlier from first sites in drier years and arriving earlier at last sites in greener years. We conclude that within the context of a strategy of itinerancy, Montagu’s Harriers are faithful to the sites they use between years (spatial component), but flexible in the timing of use of these sites (temporal component), which they adjust to annual variation in environmental conditions.
Individuals' distribution across habitats may depend on their personality. Human activities and infrastructures are critical elements of the landscape that may impact the habitat selection process. ...However, depending on their personality, individuals may respond differently to these unnatural elements.
In the present study, we first investigated whether some human infrastructures (buildings, roads and paths) shaped Montagu's harrier nest spatial distribution in the landscape according to female personality (boldness). Second, we tested if the reproductive success of females depended on their boldness and nest location regarding infrastructures.
Using a long‐term (19 years) dataset, we calculated, for each infrastructure type, the distance from each nest to the nearest infrastructure and the infrastructure density around the nest. We tested the effects of female boldness (bold vs. shy) and its interaction with egg‐laying date on these six metrics.
Nest location in the landscape depended on female personality and on some human infrastructures: the building density was smaller around nests from shy females than from bold ones. Nest distribution related to other infrastructure metrics did not depend on female boldness. The pattern related to building density is consistent with some habitat choice hypotheses, which are discussed. Path density around nests negatively affected reproductive success regardless of female boldness, and late breeders nested further away from paths than early breeders. Human activities on paths (more common later in the season) could lead to disturbance and a decrease in parental care, reducing reproductive success.
Increasing human presence in farmlands implies a need to better understand its impact on population composition, in terms of personality. Our results suggest that individual behavioural differences should be taken into account in studies assessing the effects of human disturbance on animal populations, to propose more appropriate conservation measures.
Résumé
La distribution des individus au sein de l'habitat peut dépendre de leur personnalité. Les activités et infrastructures humaines sont des éléments importants du paysage qui peuvent impacter le processus de sélection des habitats. Cependant, en fonction de leur personnalité, les individus peuvent répondre différemment à ces éléments non naturels.
Dans cette étude, nous avons d'abord examiné si certaines infrastructures humaines (bâtiments, routes et chemins) influençaient la répartition spatiale des nids de busard cendré en fonction de la personnalité des femelles (témérité). Ensuite, nous avons testé si le succès reproducteur des femelles dépendait de leur témérité et de la localisation du nid par rapport aux infrastructures.
En utilisant des données à long terme (19 ans), nous avons calculé, pour chaque type d'infrastructure, la distance de chaque nid à la plus proche infrastructure et la densité en infrastructures autour de chaque nid. Nous avons testé les effets de la témérité des femelles (téméraire vs. timide) et son interaction avec la date de ponte sur les six métriques.
La répartition spatiale des nids dépendait de la personnalité des femelles et de certaines infrastructures humaines: la densité en bâtiments était plus faible autour des nids de femelles timides qu'autour de ceux des téméraires. La distribution des nids par rapport aux autres métriques d'infrastructure n’était pas influencée par la témérité des femelles. Le patron lié à la densité en bâtiments est en accord avec certaines hypothèses de choix d'habitat qui sont discutées. La densité en chemins autour des nids affectait négativement le succès reproducteur indépendamment de la témérité des femelles, et les femelles tardives nichaient plus loin des chemins que les précoces. Les activités humaines sur les chemins (plus fréquentes tard dans la saison de reproduction) pourraient entrainer une perturbation et une diminution des soins parentaux, réduisant ainsi le succès reproducteur.
L'augmentation de la présence humaine dans les zones agricoles implique la nécessité de mieux comprendre son impact sur la composition de la population, en termes de personnalité. Nos résultats suggèrent que les différences comportementales interindividuelles devraient être prises en compte dans les études évaluant les effets des perturbations humaines sur les populations animales afin de proposer des mesures de conservations plus appropriées.
Female Montagu's harriers select nest location depending on environmental cues (buildings) and their personality: shy females nest in areas with lower building density. Although human infrastructures are in lower density in farmland compared to the urban area, anthropogenic disturbances may have an impact and should thus be taken into account for conservation measures.
Flight behaviour characteristics such as flight altitude and avoidance behaviour determine the species‐specific collision risk of birds with wind turbines. However, traditional observational methods ...exhibit limited positional accuracy. High‐resolution GPS telemetry represents a promising method to overcome this drawback. In this study, we used three‐dimensional GPS tracking data including high‐accuracy tracks recorded at 3‐s intervals to investigate the collision risk of breeding male Montagu's Harriers Circus pygargus in the Dutch–German border region. Avoidance of wind turbines was quantified by a novel approach comparing observed flights to a null model of random flight behaviour. On average, Montagu's Harriers spent as much as 8.2 h per day in flight. Most flights were at low altitude, with only 7.1% within the average rotor height range (RHR; 45–125 m). Montagu's Harriers showed significant avoidance behaviour, approaching turbines less often than expected, particularly when flying within the RHR (avoidance rate of 93.5%). For the present state, with wind farms situated on the fringes of the regional nesting range, collision risk models based on our new insights on flight behaviour indicated 0.6–2.0 yearly collisions of adult males (as compared with a population size of c. 40 pairs). However, the erection of a new wind farm inside the core breeding area could markedly increase mortality (up to 9.7 yearly collisions). If repowering of the wind farms was carried out using low‐reaching modern turbines (RHR 36–150 m), mortality would more than double, whereas it would stay approximately constant if higher turbines (RHR 86–200 m) were used. Our study demonstrates the great potential of high‐resolution GPS tracking for collision risk assessments. The resulting information on collision‐related flight behaviour allows for performing detailed scenario analyses on wind farm siting and turbine design, in contrast to current environmental assessment practices. With regard to Montagu's Harriers, we conclude that although the deployment of higher wind turbines represents an opportunity to reduce collision risk for this species, precluding wind energy developments in core breeding areas remains the most important mitigation measure.
Wildlife exposures to pest controlling substances have resulted in population declines of many predatory species during the past decades. Many pesticides were subsequently classified as persistent, ...bioaccumulative, and toxic (PBT) and banned on national or global scales. However, despite their risks for non-target vertebrate wildlife, PBT substances such as anticoagulant rodenticides (ARs) are still permitted for use in Europe and have shown to threaten raptors. Whereas risks of ARs are known, much less information is available on emerging agrochemicals such as currently used PPPs and medicinal products (MPs) in higher trophic level species. We expect that currently used PPPs are relatively mobile (vs. lipophilic) as a consequence of the PBT criteria and thus more likely to be present in aqueous matrices. We therefore analyzed blood of 204 raptor nestlings of three terrestrial (red kite, common buzzard, Montagu’s harrier) and two aquatic species (white-tailed sea eagle, osprey) from Germany. In total, we detected ARs in 22.6% of the red kites and 8.6% of the buzzards, whereas no Montagu’s harriers or aquatic species were exposed prior to sampling. ΣAR concentration tended to be higher in North Rhine-Westphalia (vs. North-Eastern Germany) where population density is higher and intense livestock farming more frequent. Among the 90 targeted and currently used PPPs, we detected six substances from which bromoxynil (14.2%) was most frequent. Especially Montagu’s harrier (31%) and red kites (22.6%) were exposed and concentrations were higher in North Rhine-Westphalia as well. Among seven MPs, we detected ciprofloxacin (3.4%), which indicates that risk mitigation measures may be needed as resistance genes were already detected in wildlife from Germany. Taken together, our study demonstrates that raptors are exposed to various chemicals during an early life stage depending on their sampling location and underpins that red kites are at particular risk for multiple pesticide exposures in Germany.
Morbidity studies complement the understanding of hazards to raptors by identifying natural or anthropogenic factors. Descriptive epidemiological studies of wildlife have become an important source ...of information about hazards to wildlife populations. On the other hand, data referenced to the overall wild population could provide a more accurate assessment of the potential impact of the morbidity/mortality causes in populations of wild birds.
The present study described the morbidity causes of hospitalized wild raptors and their incidence in the wild populations, through a long term retrospective study conducted at a wildlife rehabilitation centre of Catalonia (1995-2007). Importantly, Seasonal Cumulative Incidences (SCI) were calculated considering estimations of the wild population in the region and trend analyses were applied among the different years. A total of 7021 birds were analysed: 7 species of Strigiformes (n = 3521) and 23 of Falconiformes (n = 3500). The main causes of morbidity were trauma (49.5%), mostly in the Falconiformes, and orphaned/young birds (32.2%) mainly in the Strigiformes. During wintering periods, the largest morbidity incidence was observed in Accipiter gentillis due to gunshot wounds and in Tyto alba due to vehicle trauma. Within the breeding season, Falco tinnunculus (orphaned/young category) and Bubo bubo (electrocution and metabolic disorders) represented the most affected species. Cases due to orphaned/young, infectious/parasitic diseases, electrocution and unknown trauma tended to increase among years. By contrast, cases by undetermined cause, vehicle trauma and captivity decreased throughout the study period. Interestingly, gunshot injuries remained constant during the study period.
Frequencies of morbidity causes calculated as the proportion of each cause referred to the total number of admitted cases, allowed a qualitative assessment of hazards for the studied populations. However, cumulative incidences based on estimated wild raptor population provided a more accurate approach to the potential ecological impact of the morbidity causes in the wild populations.
Migratory species are subject to environmental variability occurring on breeding and wintering grounds. Estimating the relative contribution of environmental factors experienced sequentially during ...breeding and wintering, and their potential interaction, to the variation of survival is crucial to predict population viability of migratory species. Here we investigated this issue for the Montagu's harrier Circus pygargus, a trans‐Saharan migrant. We analysed capture–recapture data from a 29‐year long monitoring of wing‐tagged offspring and adults at two study sites in France (Rochefort‐RO and Maine‐et‐Loire‐ML). The study period covers a climatic shift occurring in the Sahel with increasing rainfall following a period of droughts (Sahel greening). We found that harriers’ adult survival in RO (between 1988 and 2005) varied over time and was sensitive to the interaction between the amount of rainfall in the Sahel and the annual mean breeding success, two proxies of prey availability. The occurrence of adverse conditions on breeding and wintering grounds in the same year decreased survival from 0.70–0.77 to 0.48 ± 0.05. Juvenile survival in RO was slightly more sensitive to conditions in Europe than in the Sahel. Unexpectedly, lower survival rates were found in years with higher mean breeding success, suggesting compensatory density feedbacks may operate. By contrast, adult survival in ML, monitored between 1999 and 2017, was higher compared to RO (0.76 ± 0.03 versus 0.66 ± 0.02), remained constant and unaffected by any proxy of prey availability. This difference seems consistent with the fact that harriers in ML experienced better and especially less variable environmental conditions during breeding and wintering seasons compared to RO. Overall, we showed that survival of a migratory bird is sensitive to the level of variability in environmental conditions and that adverse conditions on wintering grounds can amplify the negative effects of conditions during the previous breeding season on birds’ survival.
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