246 Á. Kiss et al.


these habitats. The frequency of heavy rains appears to have declined during the study period, which could also have contributed to the higher nest survival we observed over these years. Collared pratincoles breed in colonies of various sizes,


and thus we expected inter-nest distance to be an important predictor of nesting success. A similar pattern was observed by Berg (1992), who found that predation risk was negatively correlated with the number of neighbours within a breeding colony of northern lapwings. Nest predation was also nega- tively correlated with nest density in other wader species (Macdonald&Bolton, 2008). In another colonial shorebird, the pied avocet Recurvirostra avosetta, nesting success was highest at intermediate densities (Hötker, 2000), suggesting that density might have a non-linear effect on breeding success in certain cases. Several shorebird species are declining in their native


breeding habitats across Europe, having been forced to choose riskier breeding sites as their preferred habitats are converted into agriculture (Berg, 1992; Schifferli et al., 2006; Kentie et al., 2015). For the collared pratincole and similar species such as the Eurasian curlew Numenius arquata, nesting success tends to be higher in their natural habitats than in agricultural ones (Berg, 1992, Calvo, 1994; Vincent-Martin, 2007). In our study area, pratincoles only occupied agricultural habitats, which allowed us to compare the impacts of various types of human-made habitats on nesting success. However, we have no data on nest survival in the native grasslands of this species because these are now rare. In other studies that did include grasslands, higher nesting success was reported in these natural habitats (Calvo, 1994; El Malki et al., 2013). Most fields in our study site were managed in different


phases during the breeding season; therefore, the peak hatching dates occurred at different times. Nesting strategies were highly dependent on the local agricultural schedule because row crops and spring cover crops were sown first, followed by the ploughing of fallow lands. In row crops and spring cover crops, vegetation grows particularly uniformly and rapidly, reducing the time period during which the pratincoles can nest successfully. By contrast, vegetation on fallow lands grows hetero- geneously in mosaic patches, creating more suitable nesting conditions. The highest number of nests was in row crops, which was the most common type of agricultural breeding habitat available for collared pratincoles and other shore- birds at our site. The clutch size of pratincoles is similar in Hungary,


Spain (Bertolero & Martinez Vilalta, 1999) and France (Vincent-Martin, 2007) and higher than that in Ukraine and Morocco (Pozhidaeva & Molodan, 1992; El Malki et al., 2013). However, the number of successfully hatched chicks was lower than in Ukraine (Pozhidaeva & Molodan, 1992) and in Algeria (Bensaci et al., 2014).


Conservation actions


Nesting success was different between the three major breeding habitats, with the results suggesting that the most productive habitats were spring crops and fallowfields. This difference persisted even though conservation mea- sures focused on rowcrops, which increased the nesting suc- cess for this habitat. Separating the impact of conservation actions from that of the nesting habitats themselves would be difficult, as the majority of nest protection measures fo- cused only on row crops. The finding that neither daily nest survival nor total nest survival was different between habi- tats might seem counterintuitive, although the analyses that we carried out at year level (rather than at the individual nest level as in the other analyses) would have lower statistical power. Nevertheless, we only had accurate data until the chicks hatched, so we can only draw conclusions regarding the effects of the habitats from the incubation period. Direct nest protection interventions increased nest survival simi- larly to other studies, such as the wood turtle Glyptemys in- sculpta conservation project that found nesting success can be increased by designing appropriate interventions (Bougie et al., 2020). In the absence of direct nest protection, breed- ing success was probably low in critical habitats, similar to that described by Calvo (1994), who found that as a result of changing agricultural practices, nesting success also im- proved. Nesting success and the daily survival rate of nests have increased significantly over the past decade probably because of conservation actions. Although the number of culled predators did not predict


nest survival, we believe this is because of the relatively crude nature of the data (i.e. hunting bag data) and small number of sample years. Predator control is likely to be im- portant for the long-term survival of ground-nesting birds (Neuman et al., 2004; Bolton et al., 2007). We are currently designing a project to investigate the effects of predator con- trol on the nesting success of pratincoles. In addition, there are various other natural and human-induced factors that could influence the nest survival of ground-nesting birds, and we need more precise data on the effects of culling on the density of the most common nest predators. Compared with unmarked nests,we did not find increased


predation rates in nests marked with poles, similar to that observed by Zámeĉník et al. (2018), perhaps because the poles were left near nests for only short time periods. Local farmers were supportive of this nest protection, and so none of the known nests were at serious risk during agricul- tural work. However, the collared pratincole conservation project should be further improved through the establish- ment of fields and fallow lands that are free fromagricultural disturbance. As a result of the current agricultural scheme, agricultural land in Hungary and elsewhere in Europe tends to be used intensively, so arable fields are typically producing crops for most of the year (Tarjuelo et al., 2020).


Oryx, 2024, 58(2), 240–249 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323000911


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