Does the breeding biology of the Eurasian Stone-curlew Burhinus oedicnemus in south-western Morocco differ between grazed steppe and irrigated farmland?

Birds associated with steppe and pseudosteppe habitats are one of the most threatened avian communities in Europe, given their recent decline due to agriculture intensification and land abandonment. Large-scale conversion of natural and rural areas into irrigated farmlands is ongoing in North Africa, but the effects of this habitat modification on steppe bird species are not investigated. In this study, we investigated the breeding biology of the Eurasian Stone- curlew nesting in grazed steppes and irrigated farmlands in south-western Morocco. Breeding data were collected dur- ing 2017 and 2018 breeding seasons on 59 nests. Egg volume was significantly higher in grazed steppes than in irrigat- ed farmlands (37.3 ± 2.30 cm3 vs 35.1 ± 2.11 cm3, average ± SD), possibly due to greater food availability in the former habitat. On the other hand, daily nest survival over the incubation period did not differ between habitats and it was quite high (0.85 [95% CI: 0.71–0.93]) also when compared to the data available for other regions. These results suggest that birds nesting in protected areas characterized by traditional pastoralism might find better conditions for reproduction which allow them to lay larger eggs. In addition, the ongoing process of agricultural intensification in the area does not seem to affect the likelihood of nest failure. Our data add to the few available pieces of evidence regard- ing the effect of breeding habitat on the reproductive biology of the Stone-curlew in the southern range of its distribu- tion. Further data are needed in order to understand the conservation implication of our findings and, in particular, how the observed variability of egg size might affect chick quality and survival.