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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.

[EN]: Many threatened species are conserved and managed following conservation programs. These conservation programs are usually developed by intuition without assessing their biological and long-term economic sustainability. As a result, many of these programs may operate more as conservation traps rather than as conservation solutions. The current conservation program of Montagu`s harrier (Circus pygargus), a ground-nesting bird of prey, in Catalonia (NE Spain) aims to protect nests located in farmlands by delaying the harvest around the nest and compensating farmers for the economic loss associated to this measure. However, this conservation program has been flagged as a conservation trap due to the fact that its costs have been increasing over time, possibly compromising its long-term maintainability, but may need to be maintained indefinitely to have a long-term impact on the population; thus, the viability of the species is largely dependent on the duration of monetary incentives, which may be compromised. In the present work, population viability analyses were used in order to find a conservation management scenario that decreases the risk of a conservation trap, or at least minimizes the medium-term expenditure on conservation, considering simultaneously natural vegetation and agricultural breeding populations of Montagu’s harrier in Catalonia. The results hereby presented demonstrate that if the conservation goal is to maintain a self-sustainable population, it might be possible to avoid the conservation trap by increasing the population size of the natural vegetation breeding populations. However, if the conservation goal is to maintain also the agricultural breeding population, it would be impossible to fully avoid a conservation trap. Different management scenarios that might minimize the medium-term expenditure of scarce conservation funds are presented. The results obtained suggest that selecting a conservation program based only on biological or cost, [FR]: De nombreuses espèces menacées sont conservées et gérées suite aux programmes de conservation. Ces programmes de conservation sont généralement développés par intuition sans évaluer leur viabilité biologique et économique à long terme. En conséquence, plusieurs de ces programmes peuvent fonctionner comme des pièges de conservation plutôt que comme des solutions de conservation. Le programme actuel de conservation du busard cendré (Circus pygargus), une rapace nichant au sol, en Catalogne (NE Espagne), vise à protéger les nids situés dans les terres agricoles en retardant la récolte autour du nid, moyennant une indemnisation aux agriculteurs pour les pertes économiques. Cependant, ce programme de conservation a été marquée comme un piège de conservation en raison du fait que ses coûts ont augmenté au fil du temps, ce qui peut compromettre sa maintenance à long terme, mais doit être maintenu dans le temps pour avoir un effet a long-terme dans la population; donc, la viabilité de l´espèce peut être dépendant de la durabilité des budgets pour sa conservation. Dans le projet actuel, des analyses de viabilité de la population ont été utilisés afin de trouver un scénario de gestion de la conservation qui diminue le risque d'un piège de conservation, ou au moins de minimiser les dépenses à moyen terme, en tenant compte simultanément les populations reproductrices dans végétation naturelle et agricole du busard cendré dans Catalogne. Les résultats démontrent que si l'objectif de conservation est de maintenir une population autosuffisante au niveau régional, il pourrait être possible d'éviter le piège de la conservation en augmentant la taille des populations reproductrices en végétation naturelle. Toutefois, si l'objectif de conservation est aussi de maintenir les populations reproductrices agricoles, il serait impossible d'éviter totalement un piège de conservation. Différents scénarios de gestion qui pourraient réduire les dépenses des fonds de conservation à moyen t