Thread by @JYPaquet

Last week I visited Collserola NP, Barcelona, with my friend Joan Estrada. He showed me a remarkable #invasivespecies, the Red-billed Leiothrix. But then I started looking into the papers about its possible harmfulness... ⏬ #ornithology

Right pic by ucumari photography CC.

Member of Leiotrichidae (which includes Babblers and Laughingthrushes), RB Leiothrix is indigenous in Asia, introduced in Japan (despite its popular name in some languages "Rossignol du Japon"), in Hawaii and recently in several distinct areas in Europe
datazone.birdlife.org/species/factsh…

Unlike most invasive bird species, which thrive in highly anthropized landscape, RB Leiothrix selects natural habitat in its non native range - like here in Collserola broadleaf forest with dense undergrowth. Beside its nice colors, this is also why watching this bird is special

Recent spread in Catalonia is well monitored (Herrando et al 2010) from first record in 1992 to a exponential growth. Modelling of suitable habitat suggest that potential range is 36x larger than the 148km² it occupies currently tandfonline.com/doi/full/10.10…

A recent paper (Pereira et al 2019) further describes colonization pattern - from periurban forest, it could well expand to many areas in Western Europe, including Belgium where I live! But could it be a problem for native birds and ecosystems ?
doi.org/10.1007/s10530…

In Pereira's paper, there is a surprizing mention: RB Leiothrix would be "widely considered to be among the most harmful bird invaders". I was surprised because on @CABI_Invasives and other ref, nothing was so alarming
cabi.org/isc/datasheet/…

This mention of "most harmful bird invaders" is cited from a meta-analysis by Martin-Albarracin 2015 where the Leiothrix is scored the highest possible on "transmission of disease to wildlife", citing herself only one paper from van Riper III et al. (1986)
journals.plos.org/plosone/articl…

This is because in Hawaii many native species became extinct or are endangered because of avian malaria transmitted by invasive bird species. But in the van Riper paper... the RB Leiothrix was the only tested species with no malarian infection. evolution.unibas.ch/teaching/liter…

So is RB Leiothrix really a harmfull invasive? to cite Herrando et al 2010 "There is no evidence that RB Leiothrix has provoked any clear ecological disruption". For sure we need to monitor it, but is it not surprising to see how "harmfulness" is propagated across reference?

Another possible impact of this #nonnative bird is competition between RB Leiothrix and Blackcap or Robin, both common in the same habitat in Europe. It was studied in Collserola by a sophisticated technique involving stable isotope ratio doi.org/10.32800/abc.2…

.and this suggest a niche overlap between RB Leiothrix and Robin. It would be interesting to compare local pop trends of Robin and Blackcap in Collserola with the increasing trend of Leiothrix. NB: Both native species are increasing in Catalonia sioc.cat/fitxa.php?sci=… @ICOcells

@threadreaderapp unroll thanks !