[NatureNS] hummers

From: Christopher Majka <c.majka@ns.sympatico.ca>
To: naturens@chebucto.ns.ca
Date: Mon, 4 Aug 2008 10:12:07 -0300
References: <1EED5F59631C4269B948F3626FDC437C@winPC> <2E54A2E4FB2F412D9C7F0B3F8E7BC754@oldcoot3> <48960139.3050608@xplornet.com> <C2E7D007-59A2-45C2-8C36-D25F90FDAA4A@ns.sympatico.ca> <000001c8f601$9c0d80f0$d42882d0$@com> <46efb8bd0808040452k7e0e5a43s6a6da362ce51285f@mail.gmail.com> <000001c8f62c$e0ff97e0$a2fec7a0$@com>
Precedence: bulk
Return-Path: <naturens-mml-owner@chebucto.ns.ca>
Original-Recipient: rfc822;"| (cd /csuite/info/Environment/FNSN/MList; /csuite/lib/arch2html)"

next message in archive
next message in thread
previous message in archive
previous message in thread
Index of Subjects

Index of Subjects

--Apple-Mail-15--969841283
Content-Type: text/plain;
	charset=WINDOWS-1252;
	format=flowed;
	delsp=yes
Content-Transfer-Encoding: quoted-printable

Hi Flora, Suzanne and other hummingbird feeders,

On 4-Aug-08, at 9:23 AM, Wild Flora wrote:
> Like others on the list, I=92ve been seeing an unprecedented number of =
=20
> hummers this summer. I=92ve counted six on the feeders at one time, =20=

> which is double the usual number. They=92ve been going through a =20
> minimum of 3 cups of what we around here call =93hummer juice=94 (the =20=

> 1:4 sugar water) every day.
>
> Having read Chris=92s very interesting and (as always) informative =20
> post and the WildBird article, and having been unable to find any =20
> research to support the notion that higher sugar concentrations are =20=

> necessarily bad for hummers, I=92ve decided to follow the lead of =20
> another member of this list and increase the sugar concentration in =20=

> my feeders. Being a cautious person by nature, I figure I=92ll bump it =
=20
> up just a bit (to 1:3) and see how that works out.
>

For those who may be interested, here is the text of the entire post =20
(to rec.birds).

Cheers!

Chris

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - =20=

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


Since the topic of feeding hummingbirds seems to be a never-ending =20
matter of discussion and since there seems to be a plethora of =20
apocryphal knowledge drifting around on this topic (some of which I =20
myself have quoted!), I thought I would take a quick look at the =20
literature and see what is actually known on this score.

There is a very considerable body of knowledge in this area and I =20
would refer interested readers to papers such as:

Stormberg,  R. & P. B. Johnsen (1990) Hummingbird Sweetness =20
Preferences: Taste or Viscosity? Condor 92(3): 606-612.

Stiles, G.F. (1976) Taste Preferences, Color Preferences, and flower =20
Choice in Hummingbirds. Condor 78:10-26.

Miller, R. S. & R. E. Miller (1971) Feeding Activity and Color =20
Preference of Ruby-throated Hummingbirds. Condor 73: 309-313.

Collias, N. E. & E. C. Collias (1968) Anna's Hummingbirds trained to =20
select different colors in feeding. Condor 70:273-274.

There is such a wealth of information in these and other papers that =20
it's not possible to summarize it all, however, in general, =20
experiments show that there is a clear hierarchy of preference in =20
hummingbirds:

1) Of first importance is the sugar concentration and/or taste of the =20=

food.
2) Of secondary importance is the spatial position of the feeder or =20
flower.
3) Of tertiary importance is the color of the nectar.

1) Sugar Concentration and Taste

Hummingbirds clearly favor more concentrated solutions (up to a 60% =20
solution) over less concentrated ones (down to 10%). The sweeter it =20
is, the more they will be attracted to it. Two separate studies based =20=

on different metabolic, environmental and biomechanical criteria have =20=

predicted that optimal solutions for hummingbirds would be 22-26% (in =20=

one case) or 35-40% (in the second case). Note that natural sugar =20
concentrations in flower nectar tend to be in the 20% region (i.e. a =20
4:1 solution of water to sugar).

Hummingbirds seem to like both sucrose and glucose equally but greatly =20=

prefer either to fructose, which they are distinctly not fond of. This =20=

is consistent with the sugars which naturally occur in flowers =20
frequented by hummingbirds.

They show no interest at all in artificial sweeteners (saccharin, =20
aspartame, Equal). There is some question as to whether they can even =20=

taste these substances since they way in which they stimulate sweet =20
receptors in humans is not even universal in mammals, let alone birds.

2) Feeder or Flower Position

This is demonstrably less important to hummingbirds than sugar =20
concentration and/or taste. Hummingbirds will preferentially visit =20
feeders in disadvantageous positions if they contain 'good' sugar =20
solutions. In terms of position, hummingbirds prefer (unsurprisingly) =20=

positions which are close to trees where they can perch between feeding.

3) Color

Color is the least important variable for hummingbirds -- less =20
important than either sugar concentration and position. In Miller & =20
Miller's experiments (using Red, Yellow, Green, Blue & Clear =20
solutions) there was little discrimination. If anything, they seemed =20
overall to favor the clear solutions. Hummingbirds feeding in areas =20
where there are a preponderance of red flowers will somewhat favor red =20=

feeders and/or solutions, however, hummingbirds feeding
in areas where there are a preponderance of yellow flowers will =20
correspondingly favor yellow feeders and/or solutions, etc.

4) Do highly concentrated sugar solutions cause hummingbirds harm?

In my quick perusal of the literature I was unable to find any studies =20=

which tested this hypothesis. There is some evidence that very high =20
concentrations (50-60%) may be metabolized sub-optimally by =20
hummingbirds and that at such high concentrations the birds may =20
require supplementary drinking water to maintain osmotic homeostasis =20
of body fluids. As to whether it actually causes them any harm seems =20
to be (as yet) a moot point.

The studies I  refer to examined a variety of hummingbird species: =20
Ruby-throated (Archilochus colubris), Black-chinned (A. alexandri), =20
Anna's (Calypte anna) and Rufous (Selasphorus rufus) Hummingbirds,  =20
and Fork-tailed Woodnymph (Thalurania furcata).

Hopefully this will lay some myths to rest and point to areas of =20
future inquiry.

Cheers!

Christopher Majka

Christopher Majka
Nova Scotia Museum, 1747 Summer St., Halifax, Nova Scotia, Canada  B3H =20=

3A6
c.majka@ns.sympatico.ca




--Apple-Mail-15--969841283
Content-Type: text/html;
	charset=WINDOWS-1252
Content-Transfer-Encoding: quoted-printable

<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; ">Hi Flora, Suzanne and other =
hummingbird feeders,<div><br></div><div><div><div>On 4-Aug-08, at 9:23 =
AM, Wild Flora wrote:</div><blockquote type=3D"cite"><span =
class=3D"Apple-style-span" style=3D"border-collapse: separate; color: =
rgb(0, 0, 0); font-family: 'Times New Roman'; fon