The European Starling (Sturnus vulgaris) has expanded beyond its native Eurasian range, exploiting both natural cavities and human structures for nesting. We hypothesized that starling exposure to enhanced risk of nest predation at nest boxes (surrogates for nest sites in other structures), due to predator access, would negatively affect occupancy (establishment of a nest and ≥1 egg) and subsequent nest success. We also hypothesized that starlings would show no distinction in occupancy between nest boxes relative to the presence/absence of old nest material (i.e., material from the previous season), conditions that can contribute to nest predation risk. We conducted our study from April to June 2021 in Erie County, Ohio, USA, using 120 wooden nest boxes. Our treatments comprised protected/swept (nest boxes protected by a predator guard below the nest box and swept of old nest material), protected/unswept (containing old nest material), and unprotected/unswept nest boxes. To maximize sample size per treatment, we opted to forego use of unprotected/swept nest boxes, thereby preventing assessment of possible, enhanced nest predation (from below the nest box) at unprotected nest boxes due to the presence of old nest material. We used generalized linear models and nonparametric approaches in our comparisons. Starlings occupied and fledged young in unprotected nest boxes and nest boxes containing old nest material through the breeding season, despite possible, elevated perceived predation risk. There was no advantage of protection or disadvantage of presence of old nest material on reproductive metrics in protected/unswept nest boxes, because of predation from raptors (Accipitridae) and arboreal mammals (Sciuridae). The absolute amount of nest predation was, not surprisingly, highest in unprotected/unswept nest boxes across laying, incubation, and brood stages, but occurred primarily during brood rearing for protected boxes.

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