Reader Comments

Post a new comment on this article

model omits plausive alternative causes

Posted by andrewt on 16 Aug 2012 at 00:06 GMT

Our postulate that Common Myna establishment would negatively affect the abundance of small bird species was supported by our data for the Superb Fairy-wren, Striated Pardalote, Willie Wagtail, Grey Fantail, Magpie-lark, Silvereye and Common Blackbird.

The model used omits species other than mynas as causal factors but at least 2 other species in the study area, Pied Currawong & Noisy Miner have been linked to declines in small birds. Noisy Miner density isn't presented in the paper, but as measured by the GBS survey has shown a large fairly linear increase over the last 15 years. The variable used as a proxy for mynas was a linear increase over 20 years. As noted above this will correlate poorly with the presented myna desnity which follows roughly an inverted-parabola. The variable may correlate better with Noisy Miner density particularly in the last decade. The strong possibility of the confounding of impacts make the attribution of small bird decline to mynas unsupported.

No competing interests declared.

RE: model omits plausive alternative causes

KateRock replied to andrewt on 30 Oct 2012 at 09:24 GMT

We agree that competition by other species may impact native bird populations.

We used the variable of years before and years after myna as we wanted to be able to undertake a ‘before and after’ comparison. Specifically we wanted to see if bird populations changed significantly after the arrival of the Common Myna.

No model will capture the complete complexities of the natural environment.

Competing interests declared: Author