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Virtual library - harrier protection

Protection of harrier nests is the main issue in arable land. Conservationists around Europe have used a number of methods for protecting breeding harriers. However, they have different effectivity. So, what are the most effective solutions for harrier protection?

Montagu's harrier - juvenile

Only two studies from France (Santangeli, A., Arroyo, B., Millon, A., & Bretagnolle, V. (2015). Identifying effective actions to guide volunteer-based and nationwide conservation efforts for a ground-nesting farmland bird. Journal of Applied Ecology. and Spain (Santangeli, A., Minin, E. Di, Arroyo, B., & Santangeli, A. (2014). Bridging the research implementation gap–Identifying cost-effective protection measures for Montagu’s harrier nests in Spanish farmlands. Biological Conservation, 177, 126–133.) compared basic protection measures. In the study from France, the authors figured out that fenced and buffered nests together with fenced and relocated nests had higher nest productivity than nests protected with other measures and unprotected nests. Other measures were more effective in Spain. Nest relocation was the measure which has the most positive impact on the nest successful. Other measures as protection using of buffer area around the nest and delay mowing less improved harrier productivity.

All measures are cost demanding but some of them are more cost-effective. In the case of semi-colonial nesting and low compensation payment, it appears that delay mowing is the most effective measure (Santangeli et al. 2014). When nests were isolated then relocation was the most cost-effective measure and delay mowing the least cost-effective measure. However, cost-effectivity depends on labour cost in the region.  

Nestlings on the nest in the field

Expert opinions

Michal Noga - chairman of Saola - ochrana prírody (NGO), an expert on harrier conservation in Slovakia

Karel Poprach - chairman of TYTO (NGO), an expert on harrier conservation in the Czech Republic

Dominik Krupinski - chairman of TOWARZYSTWO PRZYRODNICZE “BOCIAN” (NGO), an expert on harrier conservation in Poland

Hubertus Ilner - a worker at ABU (NGO), an expert on harrier conservation in Germany

1. What is the actual population status in your country?

Michal Noga: Number of breeding pairs is very floating and it is hard to say what is the actual number of pairs. Usually, it is estimated to 5-25 pairs. We have more accurate data about the number of localized nests but this is in close relationship to the interest about the species, various number of volunteers and unequally project support during years. However, these parameters are relatively stable through the last ten years, the number of localized nests is in range 3-7. Last two years are special, we localized 9 (2018) resp. 15 nests (2019). There are regions appropriate for harriers but I expect the nesting only single pairs.   

Karel Poprach: In the Czech Republic there was confirmed nesting of 201 pairs in 2018. It is estimated at 251 - 280 pairs. Also, it is hard to estimate the development in the future. All is depending on the success of conservation measures and the reproduction - the number of flying juveniles. Whereas juveniles return to natal sites effectiveness of conservation measures is reflected on the population increasing.   

Dominik Krupinski: The total size of polish Montagu's harrier population was estimated to be 3400 breeding pairs (2700-4200). More information in this report: Kuczyński L., Krupiński D. 2014. Krajowy Cenzus Błotniaka Łąkowego. Raport końcowy. Towarzystwo Przyrodnicze "Bocian", Poznań-Warszawa.

Hubertus Ilner: The total size population in Germany is estimated for 378 pairs. 

2. What kind of measures are realized for the harrier conservation? Which are the most effective?

Michal Noga: Based on the experience, we try to make a deal with the land user. This deal is not based on any legal basis as buffer zones, compensation payments or sanctions. First, we try to postpone the date of mowing crops. This approach is not realized min. 10 years because of sooner ripening of crops. Almost every time land users have no problem with an unmowed area around the nest. Size of this area depends on the land user's willingness. Usually, it covers the area of 20x20 meters. For the protection of juveniles during harvesting time we used fences (2x2 meters, 80 cm height). Also, we apply chemical repellents (special spray against foxes) and excrements of big predators (from ZOO).   

Karel Poprach: Generally, we used fencing around the nest 2x2 m together with the repellent against predators and ensuring protection in collaboration with local farmers.

Dominik Krupinski: We protect endangered nests with fences (hexagonal net). Look at this website Not all nests are fenced, only those where the young do not fly out before the harvest. We mark all nests with a bamboo pole and works with farmers. The proven method is protection nest with hexagonal net (best 1,2 height) + reed mat (to hide chicks). Reed mat is important, gives shadow for chicks and covers the nest. Predators (foxes) can't see what's inside the fence. The fences have different size. Sometimes 1m x 1m is enough. However, bigger is better.

Hubertus Ilner: Mostly cereal harvest protection zones ( square size 50 m x 50 m), furthermore at 1/3 - 2/3 of all nests a fence (square size 1.7 m x 1.7. m, height 70 cm).

3. What is needed doing for the conservation of harriers?

Michal Noga: Ideal situation - a simple scheme of financial compensation for land users. A land user could receive 100-200 eur per protected nest. Project support could increase the interest of ornithologists about the protection of Montagu's harrier. Probably, this would be a short-term impact. On the other side, we could explore a larger area and this could establish an interest in this species by "species not focused" ornithologists and volunteers. Maintaining long-term motivation by field workers is very important because the protection of harriers (as other species) is fully depending on motivated people.

Karel Poprach: Most important is the protection of nests in arable land and the research. Monitoring of breeding success in relation to the food and other mortality factors. Ringing and the control of breeding birds is important too. The ideal scenario assumes using GSM telemetry.  

Fenced nest


Arroyo, B., García, J. T., & Bretagnolle, V. (2002). Conservation of the Montagu’s harrier (Circus pygargus) in agricultural areas. Animal Conservation.

The Montagu's harrier (Circus pygargus) is a ground-nesting raptor that breeds mainly in cereal crops in western Europe. We evaluate how the use of agricultural habitats may affect population sustainability in this species, based on simulation analyses, and explore how conservation measures could be optimized. Probability of extinction increased with decreasing harrier productivity, and this trend was accentuated when the carrying capacity (maximum number of breeding pairs) decreased. Harrier productivity in agricultural habitats is strongly affected by harvesting activities. An average of 60% of nestlings in agricultural areas of France and the Iberian Peninsula would perish in the absence of conservation measures. These losses would make populations unsustainable if no immigration occurred. Simulation analyses showed that connectivity between populations through natal dispersal could allow persistence of threatened populations even in the absence of conservation measures. The probability of extinction of four hypothetical populations connected through natal dispersal would be lowest if one of those populations were fully protected (or fully productive), even if the other ones were unprotected. Montagu's harriers are semi-colonial, and populations could be considered as a compound of subpopulations (the colonies). Additionally, Montagu's harriers bred more frequently in areas where food abundance was high, and where the number of fledgelings produced in the previous reproductive attempt was high. These factors could be used to develop sustainable and efficient conservation plans, identifying and protecting the most productive and stable colonies in agricultural areas, and further exploring experimentally factors that are likely to attract and maintain harriers in protected areas.

Belting, C., & Krüger, R. M. (2002). Populationsentwicklung und Schutzstrategien Populationsentwicklung und Schutzstrategien für die Wiesenweihe Circus pygargus in Bayern. Ornithologischer Anzeiger, 41, 87–92. Retrieved from

The Montagu's Harrier population in Germany is estimated at 250 breeding pairs. Approximately a third of them are located in Bavaria. The main population is found in "Mainfranken" with 70 pairs (in 2001). Besides some isolated pairs a smaller second population can be found in the "Nördlinger Ries" (6 pairs in 2001). The population in "Mainfranken" started with two pairs in 1994 and has grown continually since then. Except for a few pairs all of them breed in cornfields. From 1994-2001 164 out of 236 broods were successful. 539 young hatched. In Mainfranken, Montagu's Harrier breeds in a region with open fields and only slightly elevated relief. Mainly cereals and sugar beets are cultivated in this region. These are low-precipitation areas, warm in summer and with fertile soil. The nests are protected against falling stalks by metal racks. Additionally the stalks are cut around the nest in a radius of one metre. The pulli are ringed. In 2001 we started marking the young with coloured wing-tags on which we wrote consecutive numbers. If the pulli are not fully fledged when the grain harvest starts, the farmers are asked to leave a space of 50 x 50 metres with the nest in the centre. The crops are not reaped until all young are hatched. The "Naturschutzbehörde" (board for nature protection) compensates the farmers for extra time and the loss of crop. The compensation amount is usually 1278 € per hectare. The compensation agreement in the name of the Free State of Bavaria with the farmer is reached by the nest protectors.

Berger-Geiger, B., Galizia, C. G., & Arroyo, B. (2018). Montagu’s Harrier breeding parameters in relation to weather, colony size and nest protection schemes: a long-term study in Extremadura, Spain. Journal of Ornithology, (0123456789).

On the basis of long-term (2001–2017) and extensive data (> 1700 breeding attempts), we assess factors influencing breeding parameters in Montagu’s Harrier (Circus pygargus), a medium-sized ground-nesting semi-colonial raptor breeding in cereal fields, in a study area in its core distribution range (Extremadura, Spain). We evaluated annual and long-term variation in breeding parameters, as well as changes in environmental variables such as weather or harvest date. We then evaluated breeding failure and productivity in relation to nest protection measures, weather conditions, lay date and colony size. We found a significant trend for productivity to decrease over the 17-year study period, associated with a trend for predation probability to increase over time. Harvest occurred increasingly earlier in more recent years. The success rate of nests protected with unfenced unharvested patches (the most frequently used protection measure) increased with harvest date but also declined throughout the study period for equivalent harvest dates. When considering all explanatory variables together, probability of nest success decreased significantly with the lay date and throughout the study period, increased with annual rainfall and varied in relation to protective measures (being highest for nests protected with fences or where harvest in the plot had been delayed). In addition, among successful nests, fledged brood size also decreased significantly with lay date and temperature, and increased with annual rainfall. We found no effect of a number of neighbours on breeding output. We discuss our results in relation to future conservation prospects for the species.

Cardador, L., Brotons, L., Mougeot, F., Giralt, D., Bota, G., Pomarol, M., & Arroyo, B. (2015). Conservation Traps and Long-Term Species Persistence in Human-Dominated Systems. Conservation Letters, 8(6), 456–462.

Major conservation efforts in human-dominated systems, such as farmland, have focused on the establishment of subsidies and compensation promoting low-impact management practices to reverse the impacts of conservation threats in the short term (reactive approaches). In this study, we discuss how a different way of framing conservation policy (proactive approaches)could lead to fundamentally different long-term conservation outcomes. We define proactive approaches as those not necessarily including measures directly addressing the threats affecting biodiversity but promoting transitions from current scenarios in which species are threatened to new states in which the threat is no longer present. We illustrate reactive and proactive approaches using as a case study two contrasting conservation frameworks for a vulnerable farmland bird, the Montagu's harrier (Circus pygargus) in north-eastern Spain. This example shows that reactive approaches can lead to “conservation traps”, which we defined as situations where the application of biologically-focused actions in response to conservation problems results in an unsustainable need to perpetuate the implementation of those actions. Our aim is to offer a fresh perspective on biodiversity conservation in human-dominated systems and to stimulate alternative, more holistic approaches in conservation promoting transitions to new states not requiring long-term active and costly conservation action. This article is protected by copyright. All rights reserved.

Fatér, I., Tóth, L., & Tamás, E. (2004). Protection of Montagu ’ s Harrier ( Circus pygargus ) on the Heves-Borsod Plain with special attention to nesting on agricultural habitats. In Raptors worldwide.

Due to melioration activities the classical nesting habitats of Montagu’s Harrier (Circus pygargus), as wetlands, swamps have decreased drastically in the last century in Hungary. Because of the deterioration of habitats, a new nesting strategy has evolved. Cereal fields, especially winter wheat became frequented nesting sites of the birds that couldn’t find natural habitats any more. Nesting site choice differs year by year. So the number of threatened pairs also varies. At the beginning of the nesting season, almost complete protection and shading is provided by the cereals. But in the second stage of young raising these nests become endangered – in most cases the harvesting machines kill the youngs that are still unable to fly. With the determination of such endangered nests before the harvest starts, and with fencing these nests round, with a relatively small protection zone they can be saved, so the fledging of youngs can be assured. In the Heves- Borsod plain between 1995 and 2002, we have studied intensively the nesting habits of Montagu’s Harriers, and we performed protection interventions in order to save endangered nests. In the seven years of the given period, we have discovered 48 nests. 69% of the nests were found in cereal fields, and 31% on natural habitats. Out of 33 nests found in cereal fields, 71 youngs fledged (67%) thanks to protection. Out of 15 nests found in natural habitats, 11 youngs fledged (47%) without intervention. Considerable monitoring activity took place in Jász-Nagykun-Szolnok and Komárom- Esztergom counties as well.

Koks, B. J., Van Scharenburg, K. C. W. M., & Visser, E. G. (2001). Grauwe Kiekendieven Circus pygargus in Nederland: Balanceren tussen hoop en vrees. Limosa, 74, 121–136.

The Montagu's Harrier was threatened to become extinct as a breeding bird in the Netherlands towards the end of the nineteen-eighties. The province Flevoland was by far the most important region for the species between 1975 and 1989. However, the setting aside of thousands of hectares of arable land, in particular in the Oldambt region of Eastern Groningen, created a situation that was attractive to the Montagu's Harrier and other mouse-eating birds of prey because of high densities of Common Voles. Once the amount of set aside arable land began to decrease, the number of breeding pairs initially declined. However, the population more or less stabilised from the middle of the nineties onwards. The breeding population of eastern Groningen reached a maximum of 31 pairs in 2000. From about 1990 onwards most nests have been found in lucerne and winter wheat crops. Between 1975 and 1989 many more birds bred in nature reserves and tree plantations. Nowadays, the Lauwersmeer is the only remaining Dutch breeding area of any importance in which the species breeds in a semi-natural environment. In 1990-2000 the number of eggs laid by the population in Groningen averaged at 3.89[plus or minus]0.11 and the average number of fledged young was 1.51[plus or minus]0.17 young per successful pair (1.24 when based on the Mayfield method), slightly less than elsewhere in Europe. Important causes of loss are human disturbance (52%) and predation (40%). In eastern Groningen, the average number of fledglings is doubled when nests are protected from destruction due to agricultural activities. Comparison with survival estimates from southern Europe suggests that breeding productivity fully compensates for mortality only in protected nests in eastern Groningen. It seems that the Dutch population could not persist if the nests were not protected in arable land. Since 1992, the trend in numbers counted in Groningen was more positive than predicted from a model based on observed reproduction and assumed mortality, suggesting that immigration took place. We believe that the populations in Germany and Denmark act as a source of birds for the small Dutch population. This suggests that protection both here and elsewhere, as well as adequate supervision on a large scale, is necessary to maintain a stable population. Nowadays, the diet of Montagu's Harrier in eastern Groningen differs from that during the sixties and seventies of the last century. Although this opportunist still captures a broad spectrum of prey, the share of Common Voles has increased. In Groningen the proportion of voles in the diet fluctuates between 15% and 74% and there was a positive correlation between the proportion voles and both clutch size and the number of fledglings. Without nest protection, the positive effect of high vole abundance on productivity was not expressed.

Koks, B. J., & Visser, E. G. (2002). Montagu’s Harriers Circus pygargus in the Netherlands: Does nest protection prevent extinction? Ornithologischer Anzeiger, 41, 159–166. Retrieved from

The Montagu’s Harrier used to be a common breeding bird in the Netherlands. During the second half of the 20th Century a massive de? cline took place due to the fact that natural habitats like peat-moors and heaths were de? stroyed, and another important breeding habitat - the dunes - deteriorated. In the 1950’s only 250 pairs were left and at the end of the 80’s the species had become almost extinct in the Netherlands (Bijlsma et al. 2001). Due to set-aside regulations of the EU, as part of the Common Agricultural Policy of reducing the amount of grains, thousands of hectares of arable land were laid fallow. Montagu’s Harrier benefitted from this development, and from 1990 onward the Dutch population increased and between 26-45 pairs were found in the period 1990-2001 (Koks et al. 2001). In this paper the population development between 1975-2001 and the effect of nest protection in crops are described, the general results of our diet research in combination with measurements to improve the quality of the arable land for the birds.

Krupiński, D., Lewtak, J., & Szulak, K. (2010). Semicolonial nesting and conservation of the Montagu’s harrier Circus pygargus in rapeseed fields in Southern Podlasie (eastern Poland). Slovak Raptor Journal, 4(1), 37–40.

Agrocoenosis are important nest sites for Montagu's harriers. In 2009, a large semi colony of 14 Montagu's harrier pairs was recorded in a rapeseed field in eastern Poland. The breeding colony arose due to a shortage of crops of suitable height in the period of nest building, caused by unfavourable weather conditions and delayed onset of vegetation growth. The mean clutch size and hatchling number were 3.62, and the mean number of chicks in pairs that bred successfully was 2.00. Losses in broods due to predation and farming treatments were low (2% and 6%, respectively).

Krupiński, D., Lewtak, J., Rzępała, M., & Szulak, K. (2012). Breeding biology of the Montagu’s Harrier (Circus pygargus) in east-central Poland and implications for its conservation. Zoology and Ecology, 22(2), 86–92.

In 2005–2011 active conservation and study on the population of the Montagu’s Harrier was conducted in the farmland areas of east-central Poland. The population was estimated at 240–270 breeding pairs and its size was stable. The mean clutch size was estimated at 3.71 eggs per breeding pair. The number of fledgelings was 1.24 per nest and 2.6 per successful breeding pair. There were no significant differences in sex ratio. The birds nested mainly in winter cereal and rape (70%). Population productivity positively correlated with a high number of nests located in late-harvested crops. The pairs breeding in early harvested crops had significantly lower breeding success (10%) than the pairs nesting in winter cereal (>70%), due to losses during farming activities. Protection of broods with fencing had a positive effect on the breeding success of pairs nesting on arable fields. An important factor that had a negative impact on the breeding success of Montagu’s Harriers was adverse weather conditions.

Millon, A., Bourrioux, J. L., Riols, C., & Bretagnolle, V. (2002). Comparative breeding biology of Hen Harrier and Montagu’s Harrier: An 8-year study in north-eastern France. Ibis, 144(1), 94–105.

Hen and Montagu's Harriers breed in the same cultivated areas of eastern France. We present data from an extensive study conducted in three adjacent areas where 757 nests of the two harriers were monitored between 1993 and 2000, with the aim of comparing the breeding ecology of these two species and to evaluate their possible future trends. Breeding habitat for harriers consisted nearly exclusively of winter cereals, causing great conservation concern in this intensively farmed region. The Hen Harrier was almost absent from two of the study areas. This species showed the significantly larger clutch size and higher breeding success than the Montagu's Harrier, and earlier breeding phenology. It was thus less adversely affected by harvesting activities than Montagu's Harrier. Both species showed a reduced breeding success with increasing laying date. There was a large diet overlap between the two species, possibly leading to competitive interactions. Overall, the Montagu's Harrier should be considered as the more vulnerable of the two species, necessitating conservation measures, such as protection of nests from early harvesting activities. Nevertheless, to maintain both species in agricultural habitats, farming practices that preserve sufficient food should also be promoted.

Mrlík, V., Hruška, J., Poprach, K., Suchý, O., Veselý, J., & Zävalsky, O. (2002). Breeding distribution, population size, dynamics, ecology and protection of Montagu’s Harrier Circus pygargus in the Czech Republic. Ornithologischer Anzeiger, 41, 175–182. Retrieved from

Montagu’s Harrier can be classified as a species regularly breeding in the Czech Republic, with the actual population size of about 50 pairs, but the breeding population size shows considerable year-to-year fluctuation (min. 3-5 pairs). It is a raptor species with a stable population trend, yet a decline cannot be excluded. The species can be considered to be permanently threatened in the territory of the Czech Republic. In recent years (1991-2001), most nests have been situated in agricultural landscapes (88 %), rarely in semi-natural habitats such as dry or wet grasslands, meadows and/or reeds in the vicinity of fish-ponds (n = 90). In the past 11 years (1991-2001) the preferred altitude for nest sites was below 300 m (56 %). 20 % of the nests were situated at elevations of 301-400 m, and 24% at 401-500 m (n = 50). In a single case, Montagu’s Harrier nested successfully at an elevation of 610 m (in 1978). In the Czech Republic, Montagu’s Harrier is mainly a solitary breeder. Rarely, gregarious nesting of several breeding pairs was registered in some localities. In a rather small area, their nests were at least 15 m apart, and invariably the colony did not exceed 4 pairs. Our long-term estimate of the average breeding success is 1.5 young per commenced breeding (n = 151), or 2.9 young per successful nesting (n = 80/ 1929-2001). In our experience, unsuccessful nests are more frequently due to natural losses (70 %) than to man-made ones (n = 54). Most of the natural losses include nests destroyed by terrestrial predators and abandoned clutches. The man-made losses included destroyed eggs or young, one or both breeding partners killed (shot), and nests destroyed during the harvest of field crops. Protection of individual nests of these raptors need, above all, co-operation with landowners (farmers, fish-pond managers). To pre? vent losses caused by terrestrial predators it is advisable to apply such repellents as carbolic acid or naphthalene to occupied nests. Further ways of protection are discussed.

Rasmussen L. M., Sørensen I. H., Matthiesen A., Leegaard J., Christensen K. B., S. A. S. & T. N. (2018). Hedehøg i Danmark 2018. Retrieved fromøg_i_Danmark_2018.pdf

The number of breeding pairs of Montagu’s Harriers in Denmark 2018 was 24-27, all located in southwestern Jutland(Fig. 5). There were 20 confirmed pairs, of which 14 produced 48 fledglings. Additionally, there were 4 probable and 3 possible pairs. This was one pair less than in 2017, but they produced a lot more fledglings, with the third-highest number since the start of the project in 1996(Fig. 12). The number of confirmed and probable pairs was above the average of 21.1 for the 2004-2017period(Fig. 1).The weather in 2018was unusually sunny, hot and dry. Nevertheless, egg-laying started relatively late, and as late as July 25thonly half of the young had fledged. At that time, the harvesting of winter crops had long finished after starting around June20th. We found no breeding attempts in winter wheat, which traditionally is the crop housing most breeding pairs. On the other hand, a record number of 10 pairs were found in non-grazed meadows(Fig. 7). Despite intensive efforts, several clutches were lost to agricultural activities, such as the use of irrigation machines near the nestanddestruction of nestsduring harvest and grass cutting. Additionally, a few nests were lost to predation where farmers did not want located nests to be fenced. Without extensive nest protection, the total number of fledged young would probably have been significantly lower(Fig. 14). Despite the nest protection actions, it is assumed that several nests may have been lost due to harvest before it was possible for the field workers to locate and protect them. The protection could have been optimized, if all farmers had contacted the project staff immediately after becoming aware of the harrier’s presence in their crops in order to assess the possible and necessary protection measures. Good contact and trust between owners and users of areas and this project field workers, requires acontinuedmutual understanding and acceptance of the objectives of the project. In the long term, a better survival rate of the harrier fledglings will be possible, only if the food base in the farmland is increased. In addition, a greater breeding success among the successful couples would better compensate for the failed breeding attempts caused by predation and agricultural activities (Trierweiler and Koks 2009).
Santangeli, A., Arroyo, B., Millon, A., & Bretagnolle, V. (2015). Identifying effective actions to guide volunteer-based and nationwide conservation efforts for a ground-nesting farmland bird. Journal of Applied Ecology, 52(4), 1082–1091.

Modern farming practices threaten wildlife in different ways, and failure to identify the complexity of multiple threats acting in synergy may result in ineffective management. To protect ground-nesting birds in farmland, monitoring and mitigating impacts of mechanical harvesting is crucial. Here, we use 6 years of data from a nationwide volunteer-based monitoring scheme of the Montagu's harrier, a ground-nesting raptor, in French farmlands. We assess the effectiveness of alternative nest protection measures and map their potential benefit to the species. We show that unprotected nests in cultivated land are strongly negatively affected by harvesting and thus require active management. Further, we show that protection from harvesting alone (e.g. by leaving a small unharvested buffer around the nest) is impaired by post-harvest predation at nests that become highly conspicuous after harvest. Measures that simultaneously protect from harvesting and predation (by adding a fence around the nest) significantly enhance nest productivity. The map of expected gain from nest protection in relation to available volunteers' workforce pinpoints large areas of high expected gain from nest protection that are not matched by equally high workforce availability. This mismatch suggests that the impact of nest protection can be further improved by increasing volunteer efforts in key areas where they are low relative to the expected gain they could have. Synthesis and applications. This study shows that synergistic interplay of multiple factors (e.g. mechanical harvesting and predation) may completely undermine the success of well-intentioned conservation efforts. However, identifying areas where the greatest expected gains can be achieved relative to the effort expended can minimize the risk of wasted volunteer actions. Overall, this study underscores the importance of citizen science for collecting large-scale data useful for producing science and ultimately informs large-scale evidence-based conservation actions within an adaptive management framework. This study shows that synergistic interplay of multiple factors (e.g. mechanical harvesting and predation) may completely undermine the success of well-intentioned conservation efforts. However, identifying areas where the greatest expected gains can be achieved relative to the effort expended can minimize the risk of wasted volunteer actions. Overall, this study underscores the importance of citizen science for collecting large-scale data useful for producing science and ultimately informs large-scale evidence-based conservation actions within an adaptive management framework.
Santangeli, A., & Arroyo, B. (2017). The Montagu’s Harrier in Spain: Population status and trend, nesting habitat, nest protection measures and conservation solutions. Die Vogelwelt, 137(4), 372–377.

The Montagu’s harrier is a common and widespread breeding bird of the Spanish farmlands, and currently holds the most important breeding population of western Europe. The species has been the focus of conservation efforts in Spain, as well as in the rest of Western Europe, to minimize the negative impact of harvest on productivity, although there are large spatial and temporal variations in the intensity of nest protection. We provide a review summary of the current population status and trends of the species across Spain, as well as describing its distribution and main breeding habitat use. We then review the current knowledge, largely grounded on scientific evidence, on the cost-effectiveness of protection measures targeting nests of the species in cultivated landscapes in this country. We focus not only on the current costs and effectiveness of protection measures but also on the medium to long term sustainability of existing protection programmes. We discuss future avenues that could be explored in order to improve the long-term conservation status for this iconic farmland bird.

Santangeli, A., Minin, E. Di, Arroyo, B., & Santangeli, A. (n.d.). Putting science at the service of conservation practitioners-Identifying cost-effective interventions for ensuring viable populations of a ground-nesting farmland raptor.

Expensive active management programs are increasing worldwide, while resources for conservation remain scarce. There is a need to evaluate management actions so that scarce resources are used more cost-effectively. We evaluate the effectiveness of alternative interventions to protect Montagu´s harrier nests in Spanish farmlands. The species is under intensive management across Europe owing to high rates of nest destruction during mechanical harvesting operations. We use a novel approach, combining Latin hypercube sampling and population viability analysis in order to evaluate the impact of alternative protection interventions on populations' persistence across a whole range of resource allocation scenarios. We also report estimates of financial management costs for different protection interventions. Our results clearly show that, in the absence of nest protection, Spanish harrier populations would collapse to levels close to extinction within 20 years. The most cost-effective protection measures among those evaluated were the relocation or removal of the chicks and harvest delay, although this varied according to region and context. Interestingly, retention of a small un-harvested buffer around the nest, despite being widely implemented across Spain, was less cost-effective than the other two measures. Overall, we provide evidence about what measure is most effective in each studied region and what proportion of nests should be protected with such an effective measure to maintain viable populations in the medium term. We also estimate how much this effort would cost to local administrations. This is a clear example of how cost-effectiveness analyses link to applied conservation and resource allocation.
Schaub, T. W. (2015). Schutz der Wiesenweihe (Circus pygargus) im Niederen Fläming, Brandenburg. Universität Potsdam.

Stiefel, D. (2010). Zur Situation der Wiesenweihe Circus pygargus in Deutschland. Charadrius, 46(1–2), 18–27.

The surveys of breeding Montagu’s Harriers in all German federal states in 2008-2009 resulted in a total of 479 (449-488) pairs. Twelve out of 16 federal states have breeding Montagu’s Harriers. Nine states have special management programmes for the species. They pay mainly for nest protection. Most of these programmes are coordinated by the state bird conservancies or the state agencies for the protection of the environment or in some cases by non-governmental conservation organisations. The implementation is mostly done by volunteers. Beyond the highly successful nest protection measures only two states (Lower Saxony and Northrhine-Westphalia) have medium-term programmes for land use management with environmental elements to increase the availability of food for Montagu’s Harriers. Breeding in cereal fields the Montagu’s Harrier is highly dependent on such protective measures.

Torres-Orozco, D., Arroyo, B., Pomarol, M., & Santangeli, A. (2016). From a conservation trap to a conservation solution: lessons from an intensively managed Montagu’s harrier population. Animal Conservation, 19(5), 436–443.

Many threatened species in human-dominated systems are managed through conservation programs. Such programs are sometimes designed based on intuition or short-term results rather than assessing their long-term biological and economic sustainability. The current conservation program for Montagu's harriers Circus pygargus, a ground-nesting bird of prey, in Lleida (Catalonia, NE Spain) aims to protect nests located in farmlands by promoting crop harvest delay around the nest and compensating farmers for their economic loss. This program has been flagged as a ‘conservation trap’ as its costs have been increasing over time, possibly compromising the long-term sustainability of the program and associated consequences to the local harrier population. In the present work, population viability analyses (PVA) were used to find a conservation management scenario that decreases the risk of the conservation trap, or at least minimizes the medium-term expenditure on conservation. PVA simulations suggest that the current nest protection program is financially unsustainable at the medium-term. Cost-effectiveness analyses suggest that it would be impossible to fully avoid the conservation trap if the conservation goal is to maintain Lleida's current population size. Alternative management scenarios that minimize the medium-term expenditure of scarce conservation funds are presented. The results suggest that selecting a conservation program based only on short-term biological or cost-effective targets might not be the most appropriate, and demonstrate the relevance of having clear medium-term conservation targets.

Trierweiler, C., Drent, R. H., Komdeur, J., & Koks, B. J. (2010). Home range size and habitat selection of the endangered Montagu’s harrier Circus pygargus in NW-Europe: implications for conservation. In Travels to feed and food to breed: The annual cycle of a migratory raptor, Montagu’sharrier, in a modern world (pp. 2–4).

In many European landscapes that are intensively influenced by human utilization, birds increasingly rely on agricultural habitats. Montagu’s harrier Circus pygargus is an example for a diurnal raptor species that is since the middle of the 20th century mainly breeding in farmland habitats in West-Europe. The breeding season is thought to strongly affect population change in this long-distance migrant. Next to nest protection from agricultural practices, it is important to understand the functional relationship of the predator with its habitats and base conservation actions on these ecological insights. In a four – year radio telemetry study in the Netherlands, we identified lucerne, fallow habitats and cereals as most preferred habitats at different home range scale levels in two Dutch farmland areas. For hunting, high habitat diversity in general and especially intensive grasslands, lucerne, natural grasslands and fallow habitat types were most preferred. The frequency with which harriers attempted to catch prey (a measure of food availability), as well as the number of prey caught per hour (hunting yield), were highest in fallow habitats, intensive grasslands and lucerne. Individual differences in hunting yield and home range size related to differences in reproductive success. There was a trend of high proportions of lucerne and fallow habitat types in a ca. 8 km2 area (1.6 km radius) around the nest contributing to relatively small core home range size, which in turn related to high reproductive success. We recommend to offer higher proportions of these favourable habitat types in West-European intensively farmed landscapes and to optimise management of natural and extensive grasslands as habitats for potential prey populations. Because Montagu’s harrier is a top-predator, an optimised habitat management for the harrier must improve the habitat characteristics for the underlying food web, in particular, small mammal and farmland bird communities.

Melanistic female