We have a theory regarding winter nest selection by European Starlings. What we’ve noticed is that a nest put up during winter (November thru January) is poked, prodded, sampled, and in short, of extreme curiosity to European Starlings. But they seem to not want to use it; perhaps they have already selected a nest for the winter and are just investigating this newfound object.
However, while nests put up in the late fall (September, October) are subjected to the same intense scrutiny by European Starlings, these tend to be the nests that are selected for permanent residence during the winter months.
Construction of cedar nest boxes becomes somewhat of a struggle, since we’ve had birds abandon nests even if, from the opposite end of the yard, we use a circular saw to cut the boards. Sensitivity is key, and perhaps part of why they survive so well (i.e., “Fool me once, and I’m outta here…”). This would suggest a need to build the nests about 1-2 months after they are abandoned after the second round of baby birds hatching/fledging. In the Pacific Northwest, this translates to approximately mid-July/August.
Being familiar with the sounds of these little darlings makes one keenly aware when they are not in the neighborhood. We’ve put nests in certain areas with no results, and upon reflection, we never heard the birds in the area before. European Starlings seem to prefer an elevation of around 400 feet above sea level; anything 800 feet or above we haven’t seen or heard a peep from them. It could be a preference for more urban areas, however. This is all guesswork, but certainly a curiousity.