The birds had gone quiet, so now we paused only to catch our breath. Neither of us noticed the waning light until a few raindrops hit our bare arms. Overhead, tendrils of mist trailed over the jagged South Rim. Just an isolated desert shower, we thought. Nothing to worry about, surely, and the cool air feels nice.

If you’re not yet a subscriber to WildBird, you can use this link to Amazon.com to get six colorful, information-packed issues (a full year) and benefit the conservation and education programs of the Southeastern Arizona Bird Observatory (SABO). Single copies of Wildbird are also available at newsstands and bookstores. You’ll find subscriptions to WildBird and other birding magazines plus field guides, feeders and accessories, seeds for hummingbird-friendly plants, and more at SABO’s online shop, The Trogon’s Nest, powered by Amazon.com.

Lucifer Hummingbird Heart I

Wow. My polymer clay jewelry has been really well received. Most of what I’ve added to the shop in its first few weeks has already sold, and to fill demand I’ve made new versions of popular designs, including four Lucifer Hummingbird Hearts (so far). I’ve received other special orders, too. This is truly gratifying, and I thank everyone who has made a purchase from the bottom of my heart(s).

The holiday shopping season is the perfect time to start something like this, so I don’t expect this run to continue, but that’s just as well. I do art in part as a way to keep burnout at bay, so I wouldn’t want it to turn into drudgery.

There is one major but hopefully temporary change in the shop: I’ve disabled the shopping cart by marking available items as out of stock. You can still buy them, but only by contacting me directly. I regret adding this extra step to what should be a seamless process, but I no longer trust PayPal with my money. The company has a nasty habit of putting holds on customers’ accounts for extremely flimsy reasons (too few transactions, too many transactions, transactions not marked as shipped, alleged violations of the TOS, etc.), all to earn more interest off the money before its rightful owner can withdraw it.

I never used to worry when I used PayPal only to make payments. Since the Regretsy Secret Santa debacle, though, I live in fear that the company will freeze my account and deny me access to funds I need to pay for supplies and postage, buy groceries, pay bills, etc. This is predatory behavior and a serious burden to microbusinesses like mine that depend on electronic payments. Until PayPal changes the way it does business, I choose not to do business with PayPal.

At present, PayPal is the only payment option available from my storefront host, Storenvy. If that doesn’t change soon, I’ll be looking for an e-commerce alternative. In the meantime, I’ll be setting up accounts with other electronic payment services and will accept prepayment by personal check.

One positive development is that my sickly laser printer has received an overhaul and is working again. That clears the way for the next version of the Supplement to A Field Guide to Hummingbirds of North America. I’ll be busy through the end of the year with jewelry orders, Christmas Bird Counts,  field trips, etc., but watch this space early next year for the announcement that the new edition is ready.

Making and selling art will keep my mind and hands busy even if it doesn’t keep food on the table and the bankers at bay, and so I introduce you to Mountain-Gem Arts:

Mountain-Gem Arts

For the grand opening, I stocked the store with a few pieces of my own handmade polymer clay jewelry and several pots I’ve purchased from the artisans of Mata Ortiz in Chihuahua, Mexico (about a half-day’s drive from my house and a short jog off our route to the land of Thick-billed Parrots and Eared Quetzals). I sold two jewelry items in the first 24 hours the store was open and have another two reserved, so I’m walking on air.

The creative direction I’m most excited about is my Hummingbird Hearts series: The vivid colors and patterns of hummingbirds superimposed on an iconic shape.  The Ruby-throated Heart is available now, and one inspired by the Fiery-throated will be along soon. It could get pretty crazy when I take on the coquettes. I’ll also be working on sculptural bird portraits in the form of pins, pendants, and earrings as well as colorful abstract things that appeal to my ADOS (Attention Deficit Oo-ooh Shiny!). When the next edition of the Supplement to A Field Guide to Hummingbirds goes to press (= when I can afford a new laser printer), it will be available in the store as well.

If you like what you see in the current inventory and/or in my Art set on Flickr (as a taste of things to come), I hope you’ll bookmark the store for future browsing and/or “like” it on Facebook for updates on new items, discount codes, etc.

Seriously, why would someone even think of doing that?

My minimal grandson likes to conduct points with me personally so I chosen to placed an exclusive hummingbird bird feeder proper external my cooking area corner exactly where we can easily take a seat and see several hummingbirds basically we possess breakfast time, the afternoon meal, and also dinner.

Once we initially discovered the woman, she would take a flight hummingbird feeders up to in a several legs from my confront like verifying people away… or even attempting to discourage people absent.

The glass hummingbird feeders idea appeals to a range of sorts of chickens.

And they often it appears as though he’ll almost certainly start to soar at a distance, after that stop by mid-air as if to mention “Thank you” and down your dog runs.

Is “down your dog runs” anything like “Bob’s your uncle”?

The “myth” he took on is about beet sugar. Some hummingbird aficionados use only cane sugar because they claim the birds can tell the difference. I’m not convinced that this is true, so I was excited about the prospect that someone had conducted field tests to demonstrate that hummingbirds have no preference. Unfortunately, Kevin based his debunking on much flimsier evidence. He wrote:

Kitchen research in which neither cooks nor overseeing researchers knew whether they were using beet or cane sugar repeatedly showed no difference in the outcome of desserts based on the origin of the sucrose.

Taste buds, whether hummingbird or human, cannot tell beet sugar from cane sugar.

Gratuitous hummingbird photo (because I know what you crave).

Wait… what? Humans are humans, and hummingbirds are hummingbirds. There’s even a significant difference within our own species in the density of taste buds and the sensitivity to strong flavors (look up supertasters). Unless you’re putting liquified tiramisu in your feeders, how the two sugars perform in desserts has no bearing whatsoever on how hummingbirds perceive them.

What we need (and still don’t have) to debunk this myth (if myth it is) is a double-blind study presenting the birds with solutions of the same concentration in similar feeders in randomized positions, etc.

Sounds like an excellent science fair project.

The workshop is set for May 13-20, 2012 at Casa de San Pedro Bed & Breakfast, near my home in Bisbee, Arizona. Each day will start with an optional early morning field trip, including walks along the San Pedro River starting from the inn and trips to nearby hot spots such as Ramsey Canyon Preserve, followed by a full breakfast with all the trimmings. Then we’ll get down to claying!

Carol will start us out with constructing a simple kaleidoscope cane and progress to creating intricate kaleidoscope caned veneers and applying them to various objects. The “studio” will be open around the clock for “night owls,” and field trips are entirely optional for those who prefer to focus entirely on polymer clay.

Casa de San Pedro Bed & Breakfast is a favorite destination for birders and was selected by Arizona Highways Magazine as one of Arizona’s 50 Best B&Bs. It is also an official hummingbird banding station for the Southeastern Arizona Bird Observatory (SABO). Everyone will have a chance to observe research in progress, see these incredible birds up close, and even assist the banding team.

Birding clayers (and claying birders) will especially enjoy this workshop, but it’s also a fantastic opportunity for the non-birding clayer traveling with a non-claying birder spouse or companion. For more information, see the Birds and Clay page on Carol’s blog.

The gorget of a male Ruby-throated Hummingbird in mid-September consists mainly of older orange feathers with a few fresh red ones.

[Note: This is a blog post, not a peer-reviewed article, and I'm personally acquainted with the people mentioned. Therefore, I'm dispensing with the artificial formality of referring to them by their last names.]

The late-season color shift in hummingbird gorgets, a phenomenon familiar to hummingbird banders, has caught the attention of David Sibley. Unfortunately, a red herring had David barking up the wrong tree (it was an arboreal herring).

The source of the misdirection is an article in the September 2009 issue of Birding, “The Alternate Plumage of the Ruby-throated Hummingbird,” in which Donna Dittman and Steve Cardiff documented late summer/early fall molt (another phenomenon well known among hummingbird banders, though apparently none were consulted for the article). Extrapolating from Donna and Steve’s contention that Ruby-throated Hummingbirds undergo a more-or-less complete fall molt into “alternate” plumage (only to molt again in late winter—a dubious scenario), David hypothesized that the orange gorget color observed in some male Ruby-throateds in fall and winter is acquired by molt and constitutes a dull winter plumage. Comments from hummingbird banders Cathie Hutcheson and Scott Weidensaul encouraged him to reconsider, but I’d like to take this opportunity to review what we do and do not know about seasonal color changes in hummingbirds.

Though they don’t fade in the way pigment-produced colors do, the iridescent colors of hummingbirds do change over time. The exact mechanism by which this happens has yet to be documented (at least in published form), but the short answer is that it involves wear and/or bleaching rather than an additional complete molt.

To get to the long answer, it helps to know a bit of the science behind the colors. Iridescence is produced by thin layers of substances of different refractive indices, such as a film of oil on water. The refractive index is the speed at which light passes through a substance; it’s responsible for the bent appearance of a pencil in a glass of water. Refractive index values are based on the speed of light through a vacuum, which is assigned a value of 1. The higher the number, the slower the speed. The refractive index of air is 1.000293, water’s is 1.3330, and that of ordinary glass ranges from 1.523 to 1.925.

In the feathers of hummingbirds, layers of microscopic bubble-filled discs of melanin, known as platelets, are the primary source of the refractive and interference effects that create the birds’ brilliant colors. According to Crawford Greenewalt (1960), the refractive indices of the melanin and the bubbles are 2.2 and 1.0, respectively. Different colors are produced by variations in the relative thicknesses of the melanin matrix and the bubbles (the average refractive index). Thicker melanin (higher average refractive index) pushes the iridescent color toward the red end of the spectrum; larger bubbles (lower average refractive index) push it toward the violet end. Using a spectrophotometer, Greenewalt found an average refractive index of 1.85 for hummingbird feathers that iridesce red and 1.5 for those that appear blue. Following the order of colors in the spectrum, a green feather’s average refractive index would fall between 1.5 and 1.85, while the value for a violet feather would fall below 1.5.

Anna's Hummingbird gorget showing shift to coppery orange on exposed distal portions of the feathers and retention of fresh hot pink color on basal portions protected by overlying feathers.

In his follow-up post, David points out that a change in wavelength from red to orange would require a change in the thickness of the platelets. He imagines this as a collapse, but physical abrasion and/or degradation by exposure to sunlight seem like far more plausible explanations. This is supported by detailed examination of individual feathers, which show a color shift on more exposed parts and the original color on more protected parts (illustrated in the photo at right).

The change in refractive index may result from thinning of the feather’s outer layer of transparent keratin (refractive index = 1.56; Osorio and Ham 2002), complete removal of the keratin layer and abrasion of the melanin matrix of the top layer of platelets, or changes in porosity that alter the refractive index of the keratin and/or melanin. Any of these would lower the average refractive index of the iridescent structures and push the color toward the violet end of the spectrum. Over time, a feather that started out bright red would be expected to shift to orange, yellow, and perhaps even green as more of the higher refractive index material (melanin and/or keratin) is removed or degraded, and that’s what we see in nature (even in the less intense green iridescence of the back feathers, which tend to be more golden green in spring and more emerald in fall).

There’s little doubt among hummingbird banders that the shift from longer to shorter wavelengths is the result of wear and aging rather than molt, but only electron microscopy of fresh and worn feathers can reveal the mechanism responsible. I don’t personally have the resources to pay for specimen preparation and EM imaging, but if someone with deeper pockets and/or university connections can provide the microscopy services I’m sure I can round up some feathers.

References:

Dittmann, D. L. and S. W. Cardiff. 2009. The Alternate Plumage of the Ruby-throated Hummingbird. Birding 41: 32–35. Part 1 Part 2

Greenewalt, Crawford. 1960. Hummingbirds. (Dover reprint, 1990.)

Osorio, D. and A. D. Ham. 2002. Spectral reflectance and directional properties of structural coloration in bird plumage. Journal of Experimental Biology 205, 2017–2027. link