[Tweeters] new video from Sheri Williamson on hummer nectar

[Robert O'Brien]

Very interesting post.  Especially the evolutionary part about plants not
overdoing it on the sugar concentration, so that they maximize visits.
Here is a study about just such an effect with Rufous Hummers.
https://academic.oup.com/condor/article/102/1/235/5562890
Seems like plants would compete with one another for hummer attraction,
however, with those plants providing more sugar per visit beating out those
offering less. Just speculation on my part. Here is the abstract:  Bob
OBrien  Portland
Abstract

We tested concentration preferences of Rufous Hummingbirds (*Selasphorus
rufus*) offered sucrose solutions in small feeders in the field. When
sucrose solutions differing in increments of 10%, from 10% to 70%, were
presented simultaneously, hummingbirds preferred 50% to higher and lower
concentrations. They did not show a significant preference in the range
from 50% to 70% . When options were offered in pairs of choices differing
from 1–25%, hummingbirds demonstrated statistically significant preferences
that varied with mean concentration in a curvilinear manner. At
concentrations approximating those of hummingbird-pollinated flowers (20%),
hummingbirds showed greatest specificity and could distinguish solutions
differing by only 1%. At concentrations above and below 20%, greater
differences between choices were required to elicit significant preferences.

On Mon, Jan 3, 2022 at 4:16 PM Rachel Lawson <rwlawson5593 at outlook.com>
wrote:


>

> In case you still want to read more science about honey for nectar and

> nectar concentrations...

>

> This is indeed an excellent video by Sheri Williamson.  I found it

> interesting that she mentioned in passing a link between honey and tongue

> fungus, because in a previous Tweeter post, she was quoted as calling this

> "almost an urban myth".  I asked a birding friend of mine, who has spent

> her entire professional life as a food scientist and food safety expert,

> about honey and hummingbirds, and her answer surprised me.  She worries

> more about botulism than fungus.  You may remember that it is not

> recommended to feed honey to babies because of the risk of botulism.  Honey

> can contain small numbers of the spores of the anaerobic Clostridium

> bacteria that produce botulinum toxin, one of the most toxic substances

> known.  Adults and older children usually have enough stomach acid to

> kill the spores, but babies may not.  Botulism is now very rare, with an

> average of 110 cases reported in the US each year, most of them in

> infants.  However, only 25% of all cases are linked to food of any kind,

> mostly from honey or corn syrup.  A study in Poland found that only 2.1% of

> honey samples tested contained the bacteria.  Does this mean that tiny

> amounts of Clostridium spores in honey, diluted even more for nectar, are a

> potential danger to hummingbirds?  It sounds like the risk, though real, is

> very small.  But as Williamson sensibly points out in the earlier quote,

> honey is a lot more expensive than sugar, so why bother?

>

> https://www.emergency.cdc.gov/agent/botulism/clinicians/epidemiology.asp

>

> I was talking to my ornithologist-evolutionary biologist daughter last

> night about sugar concentrations in flower nectar.  To us, the interesting

> thing is how hummingbird-pollinated flowers settled on a 3 or 4 to 1

> ratio.  As hummingbirds and flowers co-evolved, they seem to have found a

> balance between the lowest concentration the hummingbirds are willing to

> accept for providing pollination services, and the highest that flowers are

> willing to provide to obtain that service.  Other pollinators may have

> arrived at different bargains with flowers.

>

> Rachel Lawson

> Seattle

> rwlawson5593 at outlook.com

>

>

>

>

>

> ------------------------------

> *From:* Tweeters <tweeters-bounces at mailman11.u.washington.edu> on behalf

> of canyoneagle at mycci.net <canyoneagle at mycci.net>

> *Sent:* Monday, January 3, 2022 7:59 AM

> *To:* 'TWEETERS tweeters' <tweeters at u.washington.edu>

> *Subject:* [Tweeters] new video from Sheri Williamson on hummer nectar

>

>

> In light of recent discussions on hummingbird nectar, I thought some of

> you might have interest in Sheri Williamson’s new video on the subject.

>

>

>

> https://www.youtube.com/watch?v=R5x4A8Db6HA

> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DR5x4A8Db6HA&data=04%7C01%7C%7C46ed0b1c77c944f837ff08d9ced2d3c1%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637768227178879860%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=a89OhzMB080Kfn9o3pWrwqX9v6a9Ifd2M0HDaOJWKjE%3D&reserved=0>

>

> Happy humming in 2022,

>

>

>

> Lori Markoff

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