Dataset for: Beyond nest occupancy: reproductive performance of Osmia caerulescens in Mediterranean orchard trap nests

This dataset contains the raw data supporting the study “Beyond nest occupancy: reproductive performance of Osmia caerulescens in Mediterranean orchard trap nests”.Data were collected from artificial trap nests installed in Mediterranean apple (AP) and pear (PR) orchards located in central Portugal. Trap nests were deployed in 13 orchards over two consecutive years (2023 and 2024) and consisted of drilled pine-wood blocks and paper-based tubes with internal diameters of 6 mm and 8 mm. Cavities were approximately 16 cm long, closed at one end, and installed along orchard edges at approximately 50 cm above ground level, oriented towards the south or east.The dataset includes cavity-level reproductive data exclusively from nests colonised by Osmia caerulescens, with each row corresponding to a single occupied cavity (Cavity ID). For each cavity, the following variables are provided: (i) total number of brood cells constructed (Brood cells); (ii) number of viable cocoons present at the time of pre-winter dissection (Viable cocoons); (iii) number of brood cells from which adult bees emerged during the summer (Emerged cocoons); (iv) number of brood cells affected by parasitism or predation (Parasitized brood cells); (v) number of brood cells containing pollen provisions or dead larvae prior to cocoon formation (Pollen loads); and (vi) number of cells containing dead adult bees (Dead adult bees).The dataset comprises records from 229 occupied cavities, yielding a total of 1,076 brood cells. Data are provided as a single CSV file and are intended to support analyses of reproductive investment, brood fate, and the relationship between nest occupation and reproductive output in solitary bees using trap nests in Mediterranean agroecosystems.