Circus Pygargus Research Articles

A conceptual model for assessing risks in a Mediterranean Natura 2000 Network site

Every year millions of tons of chemical products are disposed to the environment as a result of human activities, with deleterious consequences to biodiversity. In Europe the biodiversity policy basis for action is provided by the Birds and the Habitats Directives. According to these directives a network of protected areas is being built across EU countries encompassing the Natura 2000 Network. But the management plans of these protected areas do not require an ecotoxicological assessment of chemicals used within its limits. As for risk assessment protocols described in EC pieces of legislation and technical guidance documents, they are generic guidelines that not take into consideration regional particularities, e.g. the Mediterranean ecoregion specificities, and its local ecological values. Herewith we present a conceptual model for the assessment of risks posed by agriculture to bird species of conservationist concern from Natura 2000 Network sites; an example is set in a cereal steppe of the Iberian Peninsula. Hazards identified are related to the utilization of herbicides, disposal of sewage sludge to be used as fertilizer, and the input of veterinary pharmaceuticals that can be found in livestock dung and urine. This innovative model, to be used in high tier risk assessment, takes into account the biotic parameters of the protected bird species: great bustard ( Otis tarda), lesser kestrel ( Falco naumanni), and montagu's harrier ( Circus pygargus). The transfer of chemicals is considered to occur mainly through a realistic trophic chain scenario according to the different feeding behaviour among different species and even within the same species when having different feeding habits (e.g. adults and juveniles). Moreover, the probabilistic approach is proposed in order to perform a transparent risk assessment and clearer risk communication.

Brood‐switching in Eagle Owl Bubo bubo fledglings

Nest-switching, the (permanent or temporary) intrusion of one or several foreign young in another brood (which gener ally occurs when fledglings are capable of flight but are not yet completely independent of parents) and their sub sequent adoption by a foster family (parents + native young), has been recorded in many bird species (Riedman 1982). These include several birds of prey (Ospreys Pandion haliaetus , Poole 1982, Gilson & Marzluff 2000; Eurasian Sparrowhawks Accipiter nisus , Wyllie 1985; American Kestrels Falco sparverius , Lett & Bird 1987; Egyptian Vultures Neophron percnopterus , Donazar & Ceballos 1990; Black Kites Milvus migrans and Red Kites Milvus milvus , Bustamante & Hiraldo 1990; Northern Goshawks Accipiter gentilis , Kenward et al. 1993; Spanish Imperial Eagles Aquila adalberti , Ferrer 1993; Lesser Kestrels Falco naumanni , Tella et al. 1997; Montagu’s Harrier Circus pygargus , Arroyo & Garcia 2002) and owls (e.g. Barn Owl Tyto alba , Roulin 1999). One of the most intriguing aspects of this form of alloparental care (Riedman 1982) is the investment of resources by birds into non-genetic offspring, instead of allocating breeding effort exclusively to their own genetic contribution to future generations. Such behaviour seems incompatible with classic evolutionary theory, because it apparently violates the Darwinian principle by which selection does not act to benefit competing genotypes. To explain adoptions in birds, several hypotheses have been invoked and tested. The potential explanations for nest-switching and alloparental care form two main groups (see reviews in Redondo et al. 1995, Bize et al. 2003). First, there may be adaptive explanations such as (1) benefit to fledglings (e.g. better care than in the natal nest, acquisition of a dominant rank within a younger brood, reduction of the ectoparasite load), and (2) kin-selected benefits from a parental perspective when young switch to nests of related adults, diluting predation risk, or increasing breeding experience of related individuals. Secondly, there may be non-adaptive explanations such as reproductive errors or adoptions with negligible costs which do not affect reproductive success or survival of the foster parent. The different intensities of selection pressure for intruder chicks (surviving vs. dying) and foster parents (cost of investment in unrelated fledglings) can also be conceived of as an arms race (Pierotti & Murphy 1987). Under such a scenario, chicks are likely to ‘win’ (and consequently gain adoption) because the selection pressure is stronger than on foster parents to discriminate and reject intruders. Here, we report detailed observations of two cases of nest-switching in radiotagged Eagle Owl Bubo bubo fledglings and discuss them in an evolutionary context. Because nest-switching occurred during the post-fledging dependence period (i.e. owlets were no longer in the nest because they abandon it completely), hereafter we consider it more appropriate to replace the term nest-switching with brood-switching.

Variable but predictable prey availability affects predator breeding success: natural versus experimental evidence

AbstractFood supply is a major source of variation in breeding success for predators, and to what extent individuals are able to cope with temporal variability in food availability remains an outstanding question in life‐history studies. We confronted the natural variation in clutch size and breeding success with results from a food supplementation experiment during egg formation, conducted over several contrasted years of natural food supply in an avian specialist predator, the Montagu's harrier Circus pygargus. This raptor mainly preys on common vole Microtus arvalis a cyclic microtine under temperate latitudes. Vole abundance together with timing of breeding accounted for most of the variance in clutch size and number of fledglings. Results from empirical and experimental data were overall in agreement. Fed pairs consistently increased clutch size compared with controls in all experimental years, whereas no effect of food supplementation on egg volume was detected. Supplemented pairs, however, did not fledge significantly more chicks than controls. The costs entailed by the increase in clutch size appear nevertheless to be limited compared with previous studies. Food supply seemed therefore to display sufficient predictability throughout a breeding season to afford individuals the opportunity to adjust their breeding effort to an optimal number of offspring, in agreement with Lack's anticipation hypothesis.

Post-fledging dependence and dispersal in hacked and wild Montagu's Harriers Circus pygargus

We compared the post-fledging dependence period, dispersal patterns and resighting rates of captive-raised and hacked Montagu's Harriers Circus pygargus with those of wild reared and naturally fledged Montagu's Harriers, in order to assess the validity of haclung as a release technique for this species. Among hacked birds, we found significant relationships between the length of the dependence period and both hatching date and body condition (birds hatched later in the season had shorter periods of dependence; birds in poorer condition had longer periods of dependence). The condition index increased with the amount of time spent in captivity. The length of the dependence period did not differ significantly between released and naturally fledged birds, when hatching dates were accounted for. Observation rates of wing-tagged fledglings in years after marlung were higher for released birds (1 5.5-20.9°/~) than for naturally fledged birds (9.4-9.9940). Released birds also tended to be resighted closer to their released location than did the naturally fledged birds. We suggest that the differences in resighting data are related to the better condition of the released birds, compared with their wild counterparts. We conclude that hacking is apparently a good release technique for captive-reared Montagu's Harriers, and that comparisons of behaviour at the post-fledging period may be a valid method for evaluating the success of release techniques.

Pre-Migratory Movements of Adult Montagu's HarriersCircus pygargus

Pre-migratory and migratory movements of Montagu's Harrier Circus pygargus, a long-distance migrant, are poorly documented by ring recoveries and observations. In the present study, we tagged 10 adult Montagu's Harriers in NE Spain with satellite transmitters and tracked their movements until their arrival on the wintering grounds. To identify the end of the breeding season and the onset of the migration based on our satellite-telemetry data we developed and applied a statistical approach, defining the time period between these two events as the pre-migratory stage. We then compared habitat preferences during the breeding season and the pre-migratory stage. The duration of the pre-migratory stage averaged 42 days, with harriers leaving the breeding areas between 4 June and 27 July, and the onset of the migration taking place between 25 July and 4 September. Staging areas used during pre-migration were located at higher altitudes than the breeding grounds, and were characterized by the presence of shrublands and cultivated areas, mainly cereals. Montagu's Harriers' use of these sites is likely to be related to food availability: at higher altitudes, peak abundance of Orthoptera, their main prey source, occurs later in the season than in the lowland breeding area. Pre-migratory movements may also play an important role in the search for suitable breeding sites for future use.

Selection of nesting habitat by Montagu's Harriers Circus pygargus and Hen Harriers Circus cyaneus in managed heaths

Capsule Montagu's Harriers avoided tree plantations and selected plots with dense heath of intermediate height, while sympatric Hen Harriers preferred afforested or taller plots of heath. Aims To investigate relationships between vegetation structure and nest selection by Montagu's and Hen Harriers. Methods We defined three vegetation strata: upper, intermediate and lower. Height and cover of plant species in each stratum were recorded in a 9-m2 area centred on nests or unused random points. Statistical analysis was performed to reveal predictors for classifying plots (i) with a Montagu's Harrier nest, (ii) with a Hen Harrier nest and (iii) without a nest. Results Montagu's Harriers selected places where tree cover was less than 25%, the maximum height of the upper stratum was 1.87 m, and the cover of the intermediate stratum was greater than 75%. Hen Harriers nested either in plots where the upper stratum was higher than 1.87 m, or where tree coverage was greater than 25%. Conclusions To encourage the breeding of Montagu's Harriers, the planting of pine should be avoided and the heath should be rejuvenated before it reaches 1.80 m in height. For Hen Harriers, certain plots of heath higher than 2 m should be kept. In agricultural landscapes, patches of managed shrubland or heathland could help conservation of both species.

Breeding Ecology of Montagu'S Harrier (Circus Pygargus) in Marshes of Eastern Poland: Importance of Aggregated Nesting

Breeding success in Montagu’s Harrier (Circus pygargus) was studied in peat bogs of eastern Poland during the period 1996–2002. Harriers nested only in the area covered with great fen sedge (Cladium mariscus). The studied Harriers laid from 1 to 6 eggs, on average 4.09 eggs (n = 118). With the progression of the season, no significant decline in clutch size was recorded. The highest values of clutch size were found for pairs nesting in five nest aggregations. Harriers fledged on average 2.49 young per nest and 1.46 young per breeding pair. Early clutches in semicolonies were larger than later ones. Aggregations of five and four nests were found optimal in terms of clutch size, total loss and fledging success. The results of the study agree with the hypothesis that reproductive success may be highest at intermediate colony size.

Satellite tracking of two Montagu’s Harriers (Circus pygargus): dual pathways during autumn migration

Abstract Autumn migration routes of two Dutch female Montagu’s Harriers (Circus pygargus) were documented for the first time using satellite telemetry. Both migrated to their African wintering area—one via the Straits of Gibraltar through the Mediterranean and the other via Italy/Tunisia. The rate of travel was comparable to values reported for larger raptor species.

Interactive effects of food and age on breeding in the Montagu's Harrier Circus pygargus

We evaluated the direct and interactive effects of food and age on reproduction in the Montagu's Harrier Circus pygargus, to test whether variation in food supply was likely to affect age‐specific breeding probability or success. Younger females were more frequently non‐breeders than older females. When breeding, older females laid earlier, produced larger clutches, failed less often and had higher number of fledglings than younger females. Probability of breeding was higher, laying was earlier, and clutch size and number of fledglings per pair increased with increasing food abundance. A significant interaction between food and age was observed in both breeding probability and breeding performance: older females were more likely to breed than younger females when food abundance was low, and younger females performed less well in good food conditions than older females. Overall, differences between age groups were most marked in extreme food conditions, regardless of the quality of the conditions.

Do voles make agricultural habitat attractive to Montagu's HarrierCircus pygargus?

Loss and degradation of habitat threatens many bird populations. Recent rural land‐use changes in the Netherlands have led to a shift in habitat use by breeding Montagu's HarriersCircus pygargus. Since the 1990s, unprecedented numbers of this species have bred in farmland compared with numbers in natural habitat. Destruction of nests by agricultural operations, however, compromises breeding success. Between 1992 and 2005, the number of breeding pairs in the northeastern Netherlands was positively, though weakly, correlated with previous‐year estimated abundance of voles, mostlyMicrotus arvalis. In good vole years, the onset of laying was earlier and mean clutch size was larger. Vole abundance was relatively higher in set‐aside land and in high and dense vegetation. We suggest that agri‐environmental schemes aimed at increasing the availability of voles in agricultural breeding areas may be an effective management tool for the conservation of Montagu's Harriers in the northeastern Netherlands.

Aggressive behaviour in Montagu’s harrier Circus pygargus during the courtship period

Aggressive behaviour of Montagu’s harrier was observed during the pre-laying period in the 1992–1995 seasons on the calcareous marshes of Chelm in Eastern Poland. In total, 435 flights performed by 24 pairs of individually marked harriers were analysed. All flights were performed in relation to the territory of defence. Males performed 61% of aggressive interactions while females performed 39%. Intraspecific and interspecific aggression comprising direct attacks (58%), escorts (13%), pursuits (28%) and “mirror behaviour” (1%) were described for the first time. Interspecific aggressive behaviour occurred only near territory boundaries. The main intruders were marsh harriers Circus aeruginosus breeding on the same marshes. Occasionally, harriers attacked curlews Numenius arquata, short-eared owls Asio flammeus, magpies Pica pica, hooded crows Corvus corone cornix, common buzzards Buteo buteo or hobbies Falco subbuteo. Four cases of communal mobbing were observed. Three to five males from the neighbourhood attacked the intruders together. Intraspecific aggressive behaviour was observed in the pair territory, near the boundary or at a distance of up to 100 m from the defended area. Aggressive interactions performed by both sexes were more frequent towards birds of the same sex. Females defended their territories more aggressively against females. Similarly, males were more aggressive against males. All cases of aggressive behaviour were observed near harrier territories. Aggressive relations between birds outside breeding territories or when foraging around marshes were not observed.

Population trend and breeding biology of Montagu's Harrier Circus pygargus in a natural vegetation site in northeast Spain

Capsule Reproductive output in a natural habitat was higher than in birds breeding in cereal crops, highlighting the importance of natural habitats for the species. Aims To evaluate breeding in a natural habitat in inland Castellon province, Spain, and compare breeding parameters with other European populations. Methods Breeding population size in inland Castellon was recorded between 1981 and 2003. A logistic growth model was used to describe population increase. We also calculated clutch size, brood size, productivity, percentage of successful nests and fledging success for the period 1989–2003. Results Population size increased from three pairs in 1981 to 98 pairs in 2003. During 1989–2003, productivity (2.74 ± 1.49 fledglings/pair) and percentage of successful nests (84.%) were higher than observed in other European populations. Conclusions Our results show the importance of our study area for the conservation of this species in the Iberian Peninsula, as it might act as a source of colonists for other areas. Food and protection against predators might explain the high breeding output, which may in turn explain the rapid population growth in the area. The study also suggests that natural habitats might be important for the species elsewhere.

Density-dependent regulation of population size in colonial breeders: Allee and buffer effects in the migratory Montagu’s harrier

Expanding populations offer an opportunity to uncover the processes driving spatial variation in distribution and abundance. Individual settlement decisions will be influenced by the availability and relative quality of patches, and by how these respond to changes in conspecific density. For example, conspecific presence can alter patch suitability through reductions in resource availability or territorial exclusion, leading to buffer effect patterns of disproportionate population expansion into poorer quality areas. However, conspecific presence can also enhance patch suitability through Allee effect processes, such as transmission of information about resources or improved predator detection and deterrence. Here, we explore the factors underlying the settlement pattern of a growing population of Montagu's harriers (Circus pygargus) in Spain. The population increased exponentially between 1981 and 2001, but stabilised between 2001 and 2004. This population increase occurred alongside a remarkable spatial expansion, with novel site use occurring prior to maximum densities in occupied sites being reached. However, no temporal trends in fecundity were observed and, within sites, average fecundity did not decline with increasing density. Across the population, variance in productivity did increase with population size, suggesting a complex pattern of density-dependent costs and benefits. We suggest that both Allee and buffer effects are operating in this system, with the benefits of conspecific presence counteracting density-dependent declines in resource availability or quality.

The decline of raptors in West Africa: long‐term assessment and the role of protected areas

Comparative large‐scale roadside counts (8353 km), through Burkina Faso, Mali and Niger, conducted in 1969–73, were repeated 30–35 years later with the same observer and methodology and at the same season. The transect was divided into three geographical zones and between protected and unprotected areas. All diurnal raptors were recorded (22 801 individuals), as well as large game birds. Large vultures suffered a dramatic decline (98%) outside protected areas. The Hooded Vulture Necrosyrtes monachus population also collapsed in some regions, but survived in central Burkina Faso. Conversely, their abundance index did not decrease significantly in national parks. Four eagle species decreased by 86–93% and seven were not even recorded in the later study outside protected areas; by contrast, in national parks, only three species had declined marginally. Smaller Accipitridae (kites, goshawks, buzzards) also exhibited significant declines outside but not within national parks where woodland species reached their highest densities. The Common Kestrel Falco tinnunculus, mostly European migrants, declined sharply everywhere. African falcons decreased only outside protected areas. Among Palearctic migrants, Montagu's Circus pygargus and Pallid Harriers C. macrourus decreased significantly, Short‐toed Eagle Circaetus gallicus less markedly, and Marsh Harrier Circus aeruginosus and Booted Eagle Hieraaetus pennatus not at all. Similar trends had previously been documented in Cameroon. They are associated with human population growth and development, global habitat degradation and ecosystem impoverishment (woodcutting, agricultural intensification, overgrazing, desertification). Heavy use of pesticides, control of locust outbreaks and overhunting have suppressed major food sources. Vultures may suffer from a shortage of carcasses, poisoning for predator control or persecution for trade of meat and body parts. Protected areas play a prominent role in the maintenance of vulture and eagle populations, even though they currently cover less than 2% of the Sudan zone and are virtually absent in the Sahel.

Diet composition influences annual breeding success of Montagu's Harriers Circus pygargus feeding on diverse prey

Capsule Diet diversity was positively related to nest failure in Montagu's Harriers. Aims To evaluate whether breeding density, age structure and breeding success of Montagu's Harriers were related to variations in diet composition. Methods Breeding data were collected over an eight-year period (1991–98) in Madrid, central Spain. Diet was evaluated through pellets and remains collected near nests. Diet diversity was calculated using Shannon's index. Results Diet diversity was negatively correlated to the proportion of hares Lepus granatensis in the diet, positively to the proportion of insects, and not significantly to other prey types. Breeding parameters varied significantly between years, although annual variation in breeding parameters in Madrid was lower than in populations where diet is less diverse. Nest failure was the most important variable explaining variation in productivity, and was primarily caused by food-related factors (abandonment and starvation). Nest failure was less frequent in years where diet diversity was lower. Conclusion Hares appear to be the preferred prey for Montagu's Harriers in Madrid, and other prey were used mainly when hares were less abundant or less available (with insects being the main alternative prey). Years when diet was less diverse (i.e. when hares were dominant in the diet) were associated with a higher productivity, and with a lower between-pair variation in this parameter.

Ultraviolet reflectance by the cere of raptors

Ultraviolet (UV) signals have been shown to play key roles in social and sexual signalling in birds. Using a spectrophotometer, we analysed the colour of the cere (skin above the beak) of a diurnal raptor, the Montagu's harrier (Circus pygargus), and show that it reflects in the UV part of the spectrum. The cere is a well-known sexual signal in raptors, with carotenoid based pigmentation being indicative of quality. We thus hypothesized that UV reflectance also signals quality. Accordingly, we found that in our sample of wild males, the location of the UV peak was related to the orangeness of cere and correlated with male body mass and condition (mass corrected for size). Also, males with brighter UV were mated to females that laid earlier, as expected if UV reflectance relates to a male's quality and attractiveness. Future studies should investigate the relationships between UV reflectance and carotenoid pigmentation of cere, and test how UV reflectance influences mate choice.

Paternity assurance responses to first-year and adult male territorial intrusions in a courtship-feeding raptor

Extrapair paternity occurs in many bird species and males use mate guarding, aggression or frequent copulations to reduce the risk of losing paternity. Because paternity assurance behaviour is likely to be costly, it should be adjusted to varying levels of perceived risk. We evaluated experimentally the adjustment of paternity assurance behaviour to risk in a raptor in which courtship feeding occurs: the Montagu's harrier, Circus pygargus. We used decoys with or without prey to simulate territorial intrusions by adult or first-year males. Inexperienced first-year males should represent a lesser risk than adult males and decoys with prey should represent a greater risk than those without prey, because courtship food could be traded for extrapair copulations. Aggression was less intense towards first-year than adult males during the female's fertile period. However, when decoys were presented with prey, aggression was similar towards first-years and adults. Males increased their short-term copulation rate in response to male decoys, particularly those presented with prey. Males also increased copulation duration, but only in response to adult male decoys. Our results show that male Montagu's harriers can fine-tune their paternity assurance behaviour to varying levels of risk, in this case the type of territorial intrusion. We also discuss the implications of our findings for the adaptive significance of delayed maturation in plumage colour in this species.

Nonlinear and population‐specific offspring sex ratios in relation to high variation in prey abundance

Montagu's harrier (Circus pygargus), a specialist raptor in western France, faces huge variations in the abundance of its main prey, the common vole (Microtus arvalis). This simple predator–prey system provides fine‐tuned data for investigating patterns of sex allocation under environmental variability. We analysed variations in brood sex ratio at fledging (1364 chicks from 451 broods) in two adjacent harrier populations for respectively 16‐ and 8‐year surveys of both the predator and its prey. Overall sex ratio (number of males/total number of offspring) was close to parity (0.513) but this apparent equilibrium resulted in fact from opposite skews in the two populations which differed by almost 10% (0.561 vs 0.464). Brood reduction only is unlikely to produce such a difference in average brood sex ratios. Brood sex ratio of the predator was affected by prey abundance. Contrary to expectations and whatever the population, relatively more offspring of the smaller sex were produced during peak years of the vole cycle but also during poor years, thus providing the first evidence for a nonlinear influence of environmental quality (prey abundance) on sex ratio. Assuming that observed sex ratios in both populations are the result of an adaptive strategy that maximizes harrier reproductive output, we discuss possible origins of the bias and why nonlinearity may be involved in sex ratio adjustment. These results further point out that sex ratio analyses should take into account population characteristics, and more generally, environmental variations both in space and time.

Sjeldne fugler i Norge i 2004 - Rapport fra Norsk sjeldenhetskomité for fugl (NSKF)

This is the 28th annual report and the 29th announcement from the Norwegian Rarities Committee (NSKF). Most of the records treated here are from 2003, but older records are also included. The systematic list of accepted records is set out in the following system: (1) The bird’s Norwegian name, (2) scientific name, (3) the numbers in brackets, e.g. (30/32 - 1), refers respectively to the total number of records/total number of individuals up to and including 2002, and in 2003, (4) any limitations given of (3), (5) any breeding, (6) year, (7) county, (8) number of individuals, age (1K = first calendar year etc.), sex (if known) and sometimes circumstances («ringmerket» means that the bird was ringed), (9) site and municipality, (10) date, (11) * indicates if the record was complemented by positive evidence, and type of the evidence (F = photo, V = video-recorded, L = tape-recorded, D = found dead), (12) observers names in brackets, main observer is specified first and emphasized with *, (13) roughly gives the species general distribution and (14) comments concerning the records. General trends: This year was the second best in the history of NSKF concerning number of accepted records. Several species reached record numbers. Most significant were the influxes of Water Pipit Anthus spinoletta (17 records) and Hume’s Warbler Phylloscopus humei (10 records) during autumn. Five records of Black-necked Grebe Podiceps nigricollis , two records of Black-browed Albatross Thalassarche melanopris , four records of Balearic Shearwater Puffinus mauretanicus , six records of Bittern Botaurus stellaris , nine records of Red Kite Milvus milvus , two records of Sharp-tailed Sandpiper Calidris acuminata, six records of Mediterranean Gull Larus melanocephalus , two records of Caspian Gull Larus cachinnans and five records of Red-rumped Swallow Hirundo daurica were all maximum records for one single year. Four records of White-rumped Sandpiper Calidris fuscicollis and two records of Isabelline Shrike Lanius isabellinus were equal to previous maximum number of records. New accepted records from 2002 resulted in an increase in the maximum number of records for Great Reed Warbler Acrocephalus arundinaceus (9 records) and Blyth’s Reed Warbler Acrocephalus dumetorum (7 records). Pallid Harrier Circus macrourus (6 records), M ontagu’s Harrier Circus pygargus (6 records), Pectoral Sandpiper Calidris melanotos (12 records), Olive-backed Pipit Anthus hodgsoni (4 records) and Pallas’s Leaf Warbler Phylloscopus proregulus (20 records) were also recorded in relatively high numbers. Species and subspecies new to the Norwegian list: Two species were added to the Norwegian category A list: Yellow-legged Gull Larus michahellis and Ovenbird Seiurus aurocapillus . A record of Masked Wagtail Motacilla alba personata added a new subspecies to the Norwegian list. A record of Lammergeier Gypaetus barbatus was placed in category D and a record of Turkey Vulture Cathartes aura from 2002 was placed in category E. With these new records the official Norwegian bird list consists of 466 species. In 2003, Black-necked Grebe Podiceps nigricollis was recorded breeding in Norway for the first time with one brood successfully raised, and Pink-footed Goose Anser brachyrhynchus was recorded breeding for the first time on the Norwegian mainland excluding Svalbard).

Play behaviour and active training of Montagu?s harrier (Circus pygargus) offspring in the post-fledging period

Play bouts and active training of juveniles by Montagu’s harrier (Circus pygargus) adults in the post-fledging period were observed. Fledglings often played with prey and with a variety of inanimate objects such as bits of moss, regurgitated pellets, sticks and a wad of hay. Inanimate objects selected for play were, in length, very similar to the common vole (Microtus arvalis), which is the most common prey of the species during their breeding period. Some recently fledged individuals were trained to capture invertebrate prey by adults demonstrating techniques for the fledglings and thus develop their hunting skills. Training sessions took place only in the foraging areas of the adult birds.