What is the typical clutch size reported for Whinchats across northern populations?

Between four and six eggs.

The reproductive output of the Whinchat appears to be evolutionarily optimized and relatively stable across its diverse northern breeding range, which includes regions such as Finland, Ireland, and Austria. The standard clutch size consistently reported involves a total of four to six eggs laid per successful nest. This consistency suggests an optimal number balancing the energy demands of incubation against the short breeding window available before the arduous southward migration must commence. The female Whinchat bears the primary responsibility for incubation, which lasts approximately thirteen days, followed by the young altricial chicks remaining in the nest for another twelve to fifteen days until fledging. The male's role during this period is focused on defending the territory and providing some level of sustenance.