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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