Hi Dan,
I am curious where your information comes from. Hummingbirds turn over 2-5X
their body weight in water each and every day so it is highly unlikely that a
25% rather than a 20% sucrose solution is going to dehydrate tissues. I am now
aware of any work that even suggests this, but perhaps I have missed something.
The amount of water that hummingbirds run through their systems each day is so
high that Bill Calder stated in one of his paper back in I think the 1970’s or
80’s that the physiology of hummingbirds was more like that of fish or
amphibians than a typical terrestrial vertebrate. As for higher concentrations
of sugar (25% is still low compared to the broad spectrum of floral nectars)
hummingbirds are amazingly adept at quickly absorbing and processing it (see
the work of Bill Karasov, Todd McWhorter, and Ken Welsh) that it does not hang
around in their system long (thus the frequency with which they feed). I do
not remember the plant species, but when I was working in southern Ecuador a
few years back we found one hummingbird species that specialized on a plant
that produced low volumes of a nectar that had a rediculously high sugar
concentration (don’t recall exactly but it was over 50%) and did just fine (few
species in the Ecuadorian Andes spend much time at feeders). Body water
homeostasis is so important to pretty much all aspects of physiology that it
would be highly unusual (and selectively disadvantageous) for any species to
show long-term preference for anything that would even slight dehydrate
themselves. Just my two cents.
Actually the more interesting thing about natural floral nectar as opposed to
feeder solutions is exactly what is it about. natural nectars beyond the sugar
that is so appealing to hummingbirds? I all cercustances that I have
encountered hummingbirds will choose natural floral nectar over feeders
regardless the sugar concentration of the feeder solution. I recall on many
occasions when I was iinvolved with a large banding operation down in SE
Arizona that stations that would band 100+ hummingbirds in a morning session
would catch a total of 3 birds on days when there was a bloom somewhere on the
landscape. Perhaps it is the bit of salt and amino acids in natural nectars
(hummingbirds have a really low protein requirement…~4% of their diet so
perhaps those few amino acids are important).
Hope you all have had a great holiday season!
Cheers,
Don
------------
Donald R. Powers, Ph.D.
Professor of Biology
Department of Biological & Molecular Sciences
George Fox University
414 N. Meridian St. #6107
Newberg, OR 97132
(503) 554-2705
dpowers@xxxxxxxxxxxxx
http://www.dpowerslab.com
https://www.facebook.com/PowersLab ;<https://www.facebook.com/PowersLab>
Special Project Links
https://www.experiment.com/hothummingbirds ;
<https://www.experiment.com/hothummingbirds>
https://experiment.com/projects/how-do-hovering-hummingbirds-survive-hot-days ;
<https://experiment.com/projects/how-do-hovering-hummingbirds-survive-hot-days>
https://experiment.com/projects/do-hummingbirds-actually-sleep ;
<https://experiment.com/projects/do-hummingbirds-actually-sleep>
This e-mail and any files transmitted with it are confidential and are intended
solely for the use of the individual or entity to which they are addressed. If
you are not one of the intended recipients, any use, dissemination, forwarding,
printing, or copying of this e-mail is strictly prohibited.
On Dec 28, 2021, at 9:31 PM, Dan Gleason <dan-gleason@xxxxxxxxxxx> wrote:
There is a wide range of sugar concentrations in flowers and a wide range of
preferences in the many species of all hummingbirds. However, nectar in
flowers most attended by Anna’s Hummingbirds are on average in the range of
very slightly higher than 1: 5 ratio of sugar to water. Rufous like sweeter
flowers, 1:4 or slightly above. If given a choice, Rufous will come to 1:3 in
preference to 1:4 even though that’s a bit sweeter than their average flower
nectar. So Rufous tolerates 1:3 better than Anna’s but 1:3 will not cause
great harm to Anna’s. The higher sugar does,however, slightly dehydrate the
tissues and thus the birds come to the feeder more often to drink more to
relieve some thirst. A 1:4 mixture supplies ample sugar to met the needs of
Anna’s even in these cold temperatures. Since Rufous, which tolerates 1:3
better, is not here in the winter and Anna’s, which prefers slightly lower
sugar, is here in winter, why supply the higher sugar? It increases its
metabolic needs which it is trying to conserve. It adds some additional
stress. It can handle that but why cause it unnecessarily? In winter, Anna’s
are most attentive to feeders upon awakening from the night’s torpor and
again late in the day when they are consuming enough sugar to convert to fat
to use for energy to survive the night. During the day they still feed but
often sit fluffed up nearby a feeder so as to not expend excess energy
searching for food. Of course they still need to glean insects from plant
surfaces to obtain their needed protein. On very cold days they will go into
torpor for periods of time during the day as well as through the night as an
additional way to reduce energy use. I stay with 1:4 since that meets their
metabolic needs and Rufous that likes sweeter is not here.
Dan Gleason
Owner, Wild Birds Unlimited of Eugene
Ornithology Instructor, retired, University of Oregon
dan-gleason@xxxxxxxxxxx
On Dec 28, 2021, at 8:21 PM, larspernorgren <larspernorgren@xxxxxxxxx> wrote:
I read on Obol over ten years ago that Rufous Hummingbirds tolerate 3:1
syrup but that more than 4:1 was unhealthy for other species. No references
or explanation how this was determined. Everyone seemed to accept it as
fact.
Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------
From: Christine Maack <cmaackster@xxxxxxxxx>
Date: 12/28/21 7:32 PM (GMT-08:00)
To: Sandy Leaptrott <sandyleapt@xxxxxxxxxxx>
Cc: Obol <obol@xxxxxxxxxxxxx>
Subject: [obol] Re: Hummingbird nectar ratios
Do you know if those plants are the ones with a higher sugar content?
Chris
On Tue, Dec 28, 2021 at 7:12 PM Sandy Leaptrott <sandyleapt@xxxxxxxxxxx
<mailto:sandyleapt@xxxxxxxxxxx>> wrote:
Hello All,
Somehow I missed the nectar ratio discussion the first time around. Maybe
this explains why, even in this cold weather, my Anna's favor blooming
plants over the feeders. They use the feeders first thing in the morning
but once they get warmed up and moving around they head for the Viburnum
bodnantense, winter blooming heathers, and a winter blooming jasmine in my
garden and a neighbor's Strawberry Tree (an Arbutus of some sort).
My winter blooming plants seem to be blooming about a month early this
winter.
Sandy Leaptrott
NE Portland
Sent from my iPad
*******
UNSUBSCRIBE: www.freelists.org/list/obol <//www.freelists.org/list/obol>
OBOL archives: www.freelists.org/archive/obol
<//www.freelists.org/archive/obol>
Contact moderator: obol-moderators@xxxxxxxxxxxxx
<mailto:obol-moderators@xxxxxxxxxxxxx>
