Nest-box orientation influences reproductive outcomes and consistency in the lesser kestrel

What is it about?

Artificial nest boxes are widely used to support bird species that rely on tree cavities for nesting, especially as natural sites disappear due to habitat loss. But we still don't fully understand how the design of these boxes affects birds’ breeding over many years. In our study, we looked at 23 years of data from a colony of Lesser Kestrels in central Greece, comparing two nest-box types: vertical and horizontal. We examined how often each type was used, when breeding events occurred, how successful they were, and how consistent these outcomes were from year to year. We found that vertical boxes were used more often and had slightly better average breeding success. However, horizontal boxes provided more consistent results over time—especially in how many eggs were laid and how many chicks fledged. Timing of breeding (like when eggs were laid or chicks hatched) varied more from year to year in both box types, likely due to changing weather and environmental conditions. Our findings show that the most popular nest boxes are not always the most reliable over time. For effective conservation, it’s important to look not just at how many birds use nest boxes or how many chicks they raise in a single season, but also at how stable these outcomes are across many years.

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