Hello, tweets.

There are lots of toxic fruits. For the most part (if not
universally), those that we consider toxic are toxic to mammals only,
apparently the plant's way of ensuring its seeds to be dispersed by
birds only, as the birds can carry them farther from the plant for
better dispersal. This has been studied in Capsicum peppers, among
others by Don Norman of local fame. Birds will eat them happily,
mammals can't (except for humans, who are anything but evolutionarily
constrained by risks). It may also be that birds are better than
mammals at scarifying seeds by their bills or digestive tracts, and/
or that mammals are more likely to eat the seeds along with the fruits.

The poison in the cotoneaster that killed the waxwings must be an
unusual situation.

I'm also surprised to hear that avocado is poisonous to birds and not
mammals. Avocado is a member of the laurel family, the fruits of
which are widely eaten by parrots, toucans, cotingas, oilbirds, and
others. We of course have bred avocados for large size, and maybe
along the way we bred them for too much fat, harmful to some birds!
The legendary oilbird is thought to be oily from the laurel (and
perhaps palm) fruits that it eats.

Dennis Paulson
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net

------------------------------------------------
Date: Fri, 8 Dec 2006 18:56:52 -0800
From: "mike denny" <m.denny at charter.net>
Subject: Re: [Tweeters] birds and toxic berries

Hello All,
On 7 November 2004 while birding with John Gatchet below McNary Dam
on the
Columbia River. We watched as two tan-striped White-throated Sparrows
fed on
the beautiful eye catching red-orange fruits/berries of the Climbing
Nightshade (Solanum dulcamara). These sparrows fed on 5-7 berries each,
smashing the soft red flesh and consuming the seeds with seeming
impunity.
This plant and all of its parts are poison and contain compounds such as
solanine, glycoside,dulcamarine to name a few. So we marveled at how
these
two small bodied birds could ingest these toxins and then fly off
unaffected? See Oregon Birds 31(3):117.
Later Mike




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