Common myna: harmless presence or sinister spectre

General birdwatching discussion, help with bird identification, and all other things relating to wild birds and birding in NZ that don't fit in one of the other forums.
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Peter Frost
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Common myna: harmless presence or sinister spectre

Postby Peter Frost » Wed Jul 18, 2012 4:07 pm

Some years ago I inadvertently stuck my head into a hornets’ nest when I questioned whether our regional council should prevent the common myna from spreading beyond its current limits (see discussions on the Birding-NZ bulletin board at
http://groups.yahoo.com/group/BIRDING-NZ/messages/5901?xm=1&m=p&tidx=1).

Well, this paper may re-ignite the debate. Kate Grarock and colleagues in Canberra, Australia, using long-term data on bird abundance in and around Canberra, collected for almost 30 years by the local ornithologists' group, examined whether mynas there have a negative effect on native bird species. They use some fairly sophisticated statistical analyses to extract the patterns from their large data set (many of you may want to skip these details), but their conclusions seem clear: mynas are not benign; they have negative effects on a wide range of cavity-nesting and small-bodied native species (but not on large-bodied ones). Nevertheless, the authors are more equivocal on the question of whether trying to manage this species is a priority (a point that arose in our own discussions in 2007). But judge for yourself. The paper is:

Grarock, K., Tidemann, C.R., Wood, J., and Lindenmayer, D.B. (2012) Is it benign or is it a pariah? empirical evidence for the impact of the Common Myna (Acridotheres tristis) on Australian birds. PLoS ONE 7(7): e40622. doi:10.1371/journal.pone.0040622

Abstract: There is widespread concern over the impact of introduced species on biodiversity, but the magnitude of these impacts can be variable. Understanding the impact of an introduced species is essential for effective management. However, empirical evidence of the impact of an introduced species can be difficult to obtain, especially when the impact is through competition. Change in species abundance is often slow and gradual, coinciding with environmental change. As a result, negative impacts on native species through competition are poorly documented. An example of the difficulties associated with obtaining empirical evidence of impact due to competition comes from work on the Common Myna (Acridotheres tristis). The species is listed in the World’s top 100 worst invaders, despite a lack of empirical evidence of its negative impacts on native species. We assessed the impact of the Common Myna on native bird abundance, using long-term data both pre and post its invasion. At the outset of our investigation, we postulated that Common Myna establishment would negatively affect the abundance of other cavity-nesting species and bird species that are smaller than it. We found a negative relationship between the establishment of the Common Myna and the long-term abundance of three cavity-nesting species (Sulphur-crested Cockatoo, Crimson Rosella, Laughing Kookaburra) and eight small bird species (Striated Paradoxes, Rufous Whistler, Willie Wagtail, Grey Fantail, Magpie-lark, House Sparrow, Silvereye, Common Blackbird). To the best of our knowledge, this finding has never previously been demonstrated at the population level. We discuss the key elements of our success in finding empirical evidence of a species impact and the implications for prioritisation of introduced species for management. Specifically, prioritization of the Common Myna for management over other species still remains a contentious issue.

See the full paper or download a copy at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040622

Beyond this particular debate, the paper also illustrates the value of long-term data, collected systematically by ordinary observers using consistent methods, to reveal the changes that are occurring, albeit at rates that we might not immediately notice. If you are interested, why not take part in one or more of the Ornithological Society of New Zealand’s various recording schemes (including eBird for general recording)? Details at http://osnz.org.nz/.

Now I'm off to my bunker to dodge the flak :) .

Peter
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ledzep
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Re: Common myna: harmless presence or sinister spectre

Postby ledzep » Sun Sep 02, 2012 8:52 pm

On Mynas, I saw 3 Mynas today at the top of Robinson St (the road to Foxton Beach) in Foxton. Associating with Starlings by the road in a nearby garden. When disturbed they flew to the roof, and then off (2 north, one west). First time I've seen Mynas south of Wanganui. Maybe they are spreading southwards.
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Steps
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Re: Common myna: harmless presence or sinister spectre

Postby Steps » Mon Sep 03, 2012 9:20 am

Auckland, simply watch myna ans other birds feeding on the lawns or i the perssim tree....intimiadate starilings, thrush, black birds....the fantail flitting around will not be seen when a myna is around....the kakariki in the avairies go on alert.
much is made and blamed on rats stoats ferrit , possum, etc, and yeah rightly so...
But the effect of rossella, myna, magpie on our native birds is highly underestimated these days....50/70 yrs ago farmers knew and talked about the effects, didnt need a degree to see what was happening.... just to make it 'offical'
Becuse we dont get pictures like a possum raiding a nest....or a ferrit runing away with a kiwi...we underestimate the effect of these aggressive birds preventing the use of limitted nesting sites for our natives....instead we blame the reduced native bush due to settlers /farming....yes again also justified, but remove the myna/ magpie/ rossella from the equation and is the reduced envioroment arguement really justified?
Take these ferral birds out of the equation in our towns, Im sure many of our current native birds would be nesting in the cities instead of accasional visits from near by researves.

All that said...how do we now control these ferral bird species and at what finacual cost is NZ prepared to spend on it.
Or should we, heavans for bid, trust out young school children with air rifles AGAIN (as we did several generations ago) to plink at the mynas magpies and rossellas...as 'training school' for pig and deer stalking?

Thats a thought.. I wonder what the relationship is between every 2nd kid upto a couple generations ago, having a air rifle and spent school holidaies knocking off "bad birds"... often getting paid for it, and any increase in these populations over the last 40/50 yrs?..... we also used to get paid for rats , ferrets, rabbits possums by the local orchard owners.
How could this ever happen in this PC world? How could it be possible so many kids ran around with slug guns and hardly anyone got hit!!!.......now the kids use these slug guns ... mostly pistals, useless for any practical reason.. for shooting ppl our of cars and shooting trains....
No wonder we have game shooters who not only can ID their target , but also dont bother to make sure they have THE shot.

With these attidutes with in societry, little hope for any sort of contol over ferral bird species.
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igor
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Re: Common myna: harmless presence or sinister spectre

Postby igor » Sun Jun 23, 2013 7:09 pm

3 mynas in exactly the same spot today.

ledzep wrote:On Mynas, I saw 3 Mynas today at the top of Robinson St (the road to Foxton Beach) in Foxton. Associating with Starlings by the road in a nearby garden. When disturbed they flew to the roof, and then off (2 north, one west). First time I've seen Mynas south of Wanganui. Maybe they are spreading southwards.
Jan
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Re: Common myna: harmless presence or sinister spectre

Postby Jan » Tue Jun 25, 2013 10:01 am

Peter,

Could you come out of the bunker long enough to explain what a striated paradox is?
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Nick Allen
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Re: Common myna: harmless presence or sinister spectre

Postby Nick Allen » Tue Jun 25, 2013 8:09 pm

probably a paradox that something so beautifully and intricately marked goes around eating (slurping?) strange things called lerps

the P word seems to have been through one spell-checker too many
Pat Miller
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Re: Common myna: harmless presence or sinister spectre

Postby Pat Miller » Wed Jun 26, 2013 8:54 am

I think he means Striated Pardalote.
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Peter Frost
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Re: Common myna: harmless presence or sinister spectre

Postby Peter Frost » Thu Jun 27, 2013 12:03 pm

Just to oblige Jan: the typographical error appeared in the original abstract, since corrected by the author (see http://www.plosone.org/annotation/listThread.action?root=52179). As Nick alluded to, and Pat points out, the species referred to is the striated pardalote, Pardalotus striatus; you know, the 'invisible' bird with the repeated double-note call, tew-tewp.
More seriously, and returning to the purpose of the original post, there are some interesting criticisms of this paper from Andrew Taylor, which are worth considering. You can access these, and the senior author's responses, at http://www.plosone.org/article/comments/info%3Adoi%2F10.1371%2Fjournal.pone.0040622;jsessionid=E5B8ACA8FD0060D35581B0902C23B8DF. This is one of the merits of open-access digital publishing ;) .

Peter
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Neil Fitzgerald
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Re: Common myna: harmless presence or sinister spectre

Postby Neil Fitzgerald » Thu Jun 27, 2013 7:44 pm

I haven't read Taylor's criticisms yet. I'll do that next.
First though, I think this paper makes some excellent points, e.g., "Due to limited resources, management prioritization should be given to introduced species that have the greatest undesirable impact [12], [15]. The traditional belief that all introduced species have a negative impact can lead to wasteful allocation of resources"
and
"Community concern about the Common Myna was greater than devastating species such as the Cane Toad (Rhinella marina), Red Fox (Vulpes vulpes), Feral Cat (Felis catus) and European Rabbit (Oryctolagus cuniculus). Perhaps this is partly due to the Common Myna being abundant and visible in urban areas. Although this community passion for Common Myna management is positive, we must not let it cloud rational scientific judgment and the strategic allocation of pest management resources".
Although their conclusion is that mynas are not benign, they also point out that their impact needs to be kept in perspective. Worrying about mynas while quietly every night we have mammalian predators causing catastrophic loss of native species is like cleaning the windows while your leaky house quietly rots away.
However, I have a couple of concerns with this paper. The first is just a caution that you can't take an Aussie study and apply it directly to NZ. A couple of the species might be the same, but there are a lot more differences. My main concern though is that I'd like to see more modeling of the change in myna abundance and investigation of other covariates, because eye-balling the graph suggests that mynas followed the same pattern that the other species did, i.e., increasing at first, then declining (but with an overall increase over the study period). So, was the common myna just along for the same ride as the other cavity nesters and small birds?
Ian Southey
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Re: Common myna: harmless presence or sinister spectre

Postby Ian Southey » Thu Jun 27, 2013 9:11 pm

My understanding is that the range of Mynas in New Zealand has actually contracted although that may change.

I've never been sure that Mynas are an important limiting factor for other bird species. While they may look bad I suspect the impacts of quiet killers like cats and rats would make them look almost virtuous.

There's no point in revisiting the criticisms already given but if there is group working hard enough to remove 25000 Mynas from an area surely there's a better study investigating directly investigating the effects of that.

Ian

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