The blackbird Turdus merula is a widespread passerine whose breeding ecology in North African Mediterranean forests remains poorly documented. We investigated nest architecture, breeding performance, and spatial patterns of this species in Machroha forest (Souk Ahras province, northeastern Algeria), over four breeding seasons (2020–2023). A total of 76 nests were monitored across two forest sections (Razgoun and Mghassel). Nest height, diameter, and depth showed moderate interannual and site-specific variation, while clutch size remained stable across years. Chick production varied among years, with 2020 showing reduced fledging success. Spatial autocorrelation revealed largely random patterns both for nest placement and reproductive output, suggesting homogeneous habitat quality and territory spacing, although nest depth exhibited significant local clustering. Nest height positively influenced chick survival, whereas diameter and depth did not, highlighting the role of vertical placement in mitigating predation and optimizing microclimate conditions. PCA mixed to clustering indicated that nest size and height represented independent axes of architectural variation, reflecting the species’ behavioral plasticity. Overall, Machroha forest provides suitable breeding habitat for blackbirds, with nest architecture exhibiting adaptive flexibility and chick survival responding to subtle nest structural traits. This study fills a critical knowledge gap for North African populations, situating them within Mediterranean and European ecological contexts, and provides essential baseline data for conservation and long-term monitoring in northeast Algerian forest.