Re: Double clutching Northern rough-winged swallows
What is known is that Northern Rough-winged Swallows only nest once in a season. I assume most of the studies on the species have been conducted farther north where the breeding season is shorter. Nevertheless, unless proven otherwise, with single nesting as the known pattern it seems that your late nesting may be just that late nesting. However, I was unaware that Barn Swallows will often nest twice in a season, I have always thought of swallows as single clutch type birds. But in Barn Swallows, which are much easier to study and are much more well studied than Roughies, second nestings are known. A local pair here in Half Moon Bay is doing just that, has nestlings in the nest at this late date!
Source: SanDiegoRegionBirding Latest Reports