Maybe
here (French Polynesia and Elysée Mercier) makes him more likely.
To add a bit more details: you can see a larger view of this moss specimen [
here].
This is a specimen from the collection ("Herb." = herbier = herbarium) of Émil Bescherelle.
Émil[e] Bescherelle is the author of [
this] 1995 work, which is about mosses of Tahiti and the islands of Nukahiva and Mangareva. Therein, he cites Mercier several times (p. 12, 16, 20, 24, 58), as having collected at Nukahiva, Maquesas Is -- which is of course the same as Noukiva, and the type locality of the pigeon.
The odds that the collector of the moss is also the collector of the bird are very high. But indeed the main caveat is that "Élysée" does not appear to be written on the specimen itself -- and, if it was added
a posteriori, it might conceivably be a confusion similar to that seemingly involving "J. Mercier" on the MNHN website.
Most of the Mercier herbarium was apparently given to the Boissier herbarium after Élysée's death. What was not, passed to his son, Louis Mercier, who finally gave it to the "Conservatoire Botanique" of Geneva in 1913: see [
here], p.179. But only plants from France and Switzerland are mentioned there. Searching for "Herbier Boisset" and "Mercier" produces a fair number of results, but at first sight I see none that is about plants collected in exotic places here either. I don't think it very likely that someone who maintained his own herbarium would have given away all his specimens on his return from a far-away country, hence not seeing any suggestion that the Mercier herbarium included specimens from abroad, seems a bit odd to me.
