Hi everyone,
I’m posting this on behalf of Rose Ferrell and the Lower South West Bird Group. See forwarded message below – does anyone have any information about what could cause this? I can provide a photo if anyone is interested
Location is south-west WA
Thanks in advance, John Graff
Perth, WA
> Hi Erica, John & Robyn, > The lower south west bird group outing last month took us to a private > farming property. The owner has several feeders, and pointed out to us > the silvereyes. Several had deformed beaks. At least two were long and > decurved, and several others seemed longer than usual, but more or less > straight. > > We are seeking information about this. I am hoping you may be able to help by forwarding this to BAWA / other > appropriate people so we can get some information about this condition. > The landowner wants to know if he should stop feeding them rolled oats / > other in his feeder. > > I would be grateful for any information you can send! > Thanks for your help, > Warm regards, > Rose Ferrell > (Lower South West Bird Group)
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(University of WA) co-ordinated the studies of the Silvereyes around Margaret River in the 1980s, which resulted in the publication of several papers on their ecophysiology in the Australian Journal of Zoology.
Just to clarify … the papers published in AJZ were on the ecophysiology of the SILVEREYES, and NOT of the authors of the articles.
Stephen Ambrose Ryde NSW
PS: I can send the titles of the original papers to those who may be interested.
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Hi John,
It’s possible that it could be due to the establishment of vineyards in the Lower South-west.
Under natural situations, Silvereyes in the Marri forests feed on insects in winter, whereas in summer they are principally nectarivores, feeding principally on the nectar of the Marri flower. With the establishment of vineyards near the Marri forests, Silvereyes descend there in their thousands at the end of the summer to feed on the ripening grapes. The Silvereyes don’t enter the vineyards every year to consume the grapes, but once every 4-5 years, when the marri trees have few or no flowers. Consequently, banding studies have shown that Silvereyes in these areas have longer life-spans, surviving up to 15 years, because there is no shortage of food.
So there may be two reasons for the overgrown bills:
1. Silvereyes consuming grapes at the end of summer are less dependent on feeding on insects. I’m guessing that foraging and feeding on insects causes more abrasion of the bill than does the consumption of grapes. Therefore, individual Silvereyes that are more dependent on feeding on insects are less likely to have overgrown bills.
2. They are older and/or better nourished birds, as a result of feeding on the grapes, providing better resources for bill growth.
There are other possibilities of course: genetic mutations (either natural or induced by pesticides), disease, or malnourishment as a result of a deficiency in their diets.
Dr Ian Rooke (WA Dept of Agriculture) and Professor Don Bradshaw (University of WA) co-ordinated the studies of the Silvereyes around Margaret River in the 1980s, which resulted in the publication of several papers on their ecophysiology in the Australian Journal of Zoology. A comprehensive summary and synthesis of those studies is presented in Bradshaw (2003).
Hope this information helps.
Regards, Stephen Ambrose
Reference
Bradshaw, S.D. (2003). Vertebrate Ecophysiology: An Introduction to its Principles and Application (Cambridge University Press, Cambridge).
Hi John,
It’s possible that it could be due to the establishment of vineyards in the Lower South-west.
Under natural situations, Silvereyes in the Marri forests feed on insects in winter, whereas in summer they are principally nectarivores, feeding principally on the nectar of the Marri flower. With the establishment of vineyards near the Marri forests, Silvereyes descend there in their thousands at the end of the summer to feed on the ripening grapes. The Silvereyes don’t enter the vineyards every year to consume the grapes, but once every 4-5 years, when the marri trees have few or no flowers. Consequently, banding studies have shown that Silvereyes in these areas have longer life-spans, surviving up to 15 years, because there is no shortage of food.
So there may be two reasons for the overgrown bills:
1. Silvereyes consuming grapes at the end of summer are less dependent on feeding on insects. I’m guessing that foraging and feeding on insects causes more abrasion of the bill than does the consumption of grapes. Therefore, individual Silvereyes that are more dependent on feeding on insects are less likely to have overgrown bills.
2. They are older and/or better nourished birds, as a result of feeding on the grapes, providing better resources for bill growth.
There are other possibilities of course: genetic mutations (either natural or induced by pesticides), disease, or malnourishment as a result of a deficiency in their diets.
Dr Ian Rooke (WA Dept of Agriculture) and Professor Don Bradshaw (University of WA) co-ordinated the studies of the Silvereyes around Margaret River in the 1980s, which resulted in the publication of several papers on their ecophysiology in the Australian Journal of Zoology. A comprehensive summary and synthesis of those studies is presented in Bradshaw (2003).
Hope this information helps.
Regards, Stephen Ambrose
Reference
Bradshaw, S.D. (2003). Vertebrate Ecophysiology: An Introduction to its Principles and Application (Cambridge University Press, Cambridge).