This ‘restoration’ issue of Vespasian takes its inspiration from this republican type (RRC 287/1):
The literary sources only have woodpeckers associated with the wolf and twins narrative (Ovid, Fasti 3.37 and 54). One type of woodpecker with a crest was known as Mar’s Woodpecker hence the connection (Pliny NH 11.44). But that doesn’t mean other birds aren’t found in art. More than I want to list here. But just as a taster. Here’s an eagle on a glass paste to which we might compare the Ostian Altar:
And another glass paste with a ‘non-descript’ bird on a grape vine (NOT the ficus Ruminalis then):
This last is a pretty common type of image. Sometimes the grape vine has a bird, sometimes not.
Then there are the other republican coins (RRC 39/3 and 235/1) and that mirror we discussed ages ago that should be brought into the discussion but I’ll leave it there for now. Except for just wondering if this weird BM gem with a mysterious head in the scene might not be Roma’s head, like a reverse scaling of the Roma plus wolf-and-twins motif above:
Update 2/5/2014: The important bibliography on this is
A. Dardenay, Les intailles républicaines figurant la louve romaine: essai d’identification des modèles iconographiques. Pallas 76, 2008, 101-113.
Of course, I had this on file the whole time but didn’t remember the relevance until today….