When European Goldfinches eat thistles,
the seeds would not remain viable after passing through the bird. These birds feed on and digest
the seed. There is no fruit available to digest. It is not like a Mistletoebird or an Emu in which the fruit is digested and the plant is adapted with seeds to be unaffected (or even improved) by passing through a bird. The difference is based on whether the
plant’s strategy is to provide a big fruit surrounding a seed to entice animals to eat the fruit and disperse the seed.
About Likewise are blackberry seeds viable in the wake of Common Blackbirds,
I suspect that, as the seeds are tiny on big fruits, the bird obtains most of the benefit by digesting the fruit and that given this belief, very likely some of the vast number of seeds would pass through the bird still capable of germinating. An experiment
would easily demonstrate this.
Philip
From: John Layton [
Sent: Friday, 19 August, 2016 12:46 PM
To: Canberra birds
Subject: [canberrabirds] European goldfinch - thistle controller or spreader?
There seems something of a consensus that European Goldfinches control thistles, but I’ve often wondered if this is so, or do the seeds remain viable after passing through
the bird?
Likewise are blackberry seeds viable in the wake of Common Blackbirds? A species widely blamed for the spread of the brambles.
John Layton
Holt.
