Host plants:
The larvae are polyphagous, but prefer grasses. I also observed a lot of larvae below Scrophularia auriculata with feeding scars.
Habitat:
I observed the larvae (more than 50) in the uplands of Saint Miguel above 600m asl, especially in and at the margin of forests. The highest larval densities were recorded on grassy clearings and along partly sunny forest roads. The kind of forest does not play a significant role provided they are not too dense and thus too dark. Noctua atlantica depends on clearcuts, road sides and young plantations in the dark allochthonous coniferous forests. Originally the specie might have settled in the laurel forests. Noctua pronuba is most often syntopic.
In literature also observations (at light) are known from low altitudes.
Life cycle:
I recorded the larvae in various instars (L1 to mature) in November and December 2013. Probably Noctua atlantica can build up several generations throughout the year, but with a peak of moths between March and June.
Young larvae often stay on the host plant during daytime (especially on grasses), but somewhat sheltered and not exposed. The older ones are strictly nocturnal and hide near the ground and sometimes even bury themselves superficially below or around the hostplant or conceal in the moss layer.
Endangerment factors:
The main threats is the expulsion of woodlands by intense cattle pastures. Within the still existing woodlands dark forest management with foreign conifers is a major problem. Noctua atlantica can survive only if there are still clearcuts and semi-open places in these coniferous forests. Probably also frequent hybridization with Noctua pronuba could be another problem, even if a more natural one.
Remarks:
Noctua atlantica is endemic to the Azores (Portugal) and can be observed on most islands except Santa Maria.
Hints on determination:
The larvae are very similar to the syntopic Noctua pronuba, but considerably smaller. Hybridization with N. pronuba seems to be common. Resulting moths also show darkened hind wings, but often not so heavily, and they are much larger (more like N. pronuba). The true N. pronuba with its orange hind wings is common in the Azores, too (see photos in that species).