Moths in bird nests

Contents of several nest boxes

In October 2013 I collected the contents of several vacated nest boxes. I stored the nest material and general detritus in sealed tubs over the winter. The hope was that there would be moth pupae within the detritus. There are quite a number of British species associated with bird nests, the larvae probably feeding on detritus or fibers.

Fast forward to spring 2014 when adults began to emerge from the tubs. Within a couple of months the following had appeared:

52x Monopis laevigella
19x Niditinea striolella
11x Endrosis sarcitrella
2x Nemapogon wolffiella

Monopis laevigella, Niditinea striolella & Nemapogon wolffiella

Monopis laevigella is clearly an abundant species. I've occasionally seen the species free-flying outside, often by day, but never in large numbers. Andrew Graham comments on such numbers emerging from owl nests on his website. It also was interesting to note that none of the laevigella presented any issues separating from M. weaverella: the main confusion species. The two can look extremely similar at times but the 52 exhibited all the features of laevigella without exception.

Niditinea striolella is quite a difficult species to identify. When I potted the first one, I knew it was a species I'd not seen before. Clearly a tineid and a look in the books suggested the Niditinea genus as a likely candidate. N. fuscella appears to be the commoner species, however I felt my moth resembled striolella more closely. The two species can be very similar, as well as confused with other members of the family. To be certain of the identification, I checked its genitalia which are quite distinct. This confirmed the identification of Niditinea striolella: a nationally scarce B species and the first record for the county,  and indeed all of north Wales. Many more emerged over a three-week period, during this time, I selected a few individuals for gen det to ensure the emergence consisted of this single species. The large numbers which emerged suggests this is a locally common species and is probably more widespread. To find 19 individuals from a few bird nests but not a single one in five years moth trapping suggests the species is very easily overlooked.

Endrosis sarcitrella was definitely an expected species being common in moth traps, as well as indoors.

Nemapogon wolffiella was, however, a real surprise. I first came across this nationally scarce B species a few years ago when I found the first county record in the house. I've since discovered it to be fairly regular when netting late afternoon in a wooded part of the garden. Also occurs very infrequently in moth traps. It was a surprise because the literature states it feeds on dead wood and bracket fungi and therefore should not be found in bird nests. It's possible the species feeds on decaying matter within bird nests, like many other members of the family. Another possible explanation is the larvae had been feeding on dead wood but moved into the bird box to pupate.

There were a number of species I felt were missing. For example Tinea trinotella and T. semifulvella are both fairly regular in moth traps here (more so than M. laevigella)  and both are said to feed in bird nests, however none emerged. This is quite possibly just a case of sampling error and collecting a larger number of nests may well produce more species. Alternatively, the conditions in the tubs might not have been right for these species over winter and these pupae died or otherwise failed to emerge. Also possible that those two species prefer different types of nest e.g. nests in hedgerows.

Collecting nest material in the autumn certainly seems likely a worthwhile undertaking. There are at least 10 species, probably more, given in the literature that feed in bird nests. Many of these are likely to be very under-recorded. If nothing else, the whole exercise enlightened me that birds have at least one purpose after all...


Douglas.