The Wren Conundrum

New Zealand wrens, the Acanthisittidae, are an odd bunch. They don’t seem to fit into the traditional bird phylogenetic tree, and they certainly aren’t particularly similar to the old world wrens Certhioidea. Studies have shown that they are more “basal” (as Dr Jamie Wood puts it), or a sister group to the Eupasseres (all the other Passerines, or perching-birds). Three of these wrens were the world’s only flightless songbirds. I found a great article on the Scientific American website which explains the Passerine bird groups.

Simplified passerine phylogeny showing only major lineages, the more important group names shown in bold. Credit: DARREN NAISH. Taken from http://bit.ly/2nysVOJ

Rock Wren, left (from http://www.indileak.com); Rifleman, right (from nzbirdsonline.org.nz)

The New Zealand wrens are represented by only seven known species, of which only two survive today—the Rock Wren Xenicus gilviventris and the Rifleman Acanthisitta chloris (see image, above). The Rock Wren’s closest relative, the Bush Wren , has the unfortunate distinction of being one of New Zealand’s most recent extinctions, the last reliable sighting was in 1972. The sad story of a lighthouse keeper’s cat (called Tibbles) single-handedly (pawedly?) exterminating the last remaining colony of Lyall’s Wren Traversia lyalli at the end of the twentieth century, is unlikely to be wholly true, they had probably been predated upon by several feral cats in addition to the bird skins becoming highly collectible items. I found this paper which relates the whole sorry affair:

Two very closely related species, the North Island Stout-legged Wren Pachyplichas jagmi and the South Island Stout-legged Wren Pachyplichas yaldwyni, may in fact be just different forms of the same species. This is still to be decided, but as the birds sub fossils appear to be from sediment dated as late Pleistocene-Holocene, there is not exactly a lot of data to go on.  And finally, the most rare species of these little birds, the Long-billed Wren Dendroscansor decurvirostris. The “Checklist of the Birds of New Zealand” (4th ed.), which Dr Wood called the “Bird Bible”, states:

Fossil bones have been found at only four sites (caves in north-west Nelson and Southland) and belong to fewer than six individuals in total.

Strangely enough, the other day I held in my hands four little vials, on loan to us from the Canterbury Museum, found in cave deposits from Mount Nicholas. One was labelled “?”, and two were labelled “D. decurvirostris-?”. I was possibly handling the remains of one of the rarest birds in New Zealand’s history and we had been given permission to attempt to extract aDNA from them. If any of them were identified genetically as coming from one of the tiny wrens, it would be a very significant find, potentially increasing the number of individuals discovered to the huge number of seven. The next post will cover how the aDNA was extracted, and maybe even some tentative results…

…to be continued