Sunday, October 5, 2014

Ruby Delights

I spent the weekend in the company of this presumed hatch year (HY) male Ruby-throated Hummingbird. 



I had been resigned to thinking my feeders would no longer host anymore hummingbirds for the year when two appeared in the yard on Friday afternoon. I spent time photographing and digiscoping one of the birds which I concluded was likely a hatch year male. While aging Ruby-throated Hummingbirds in the field is challenging since seeing bill corrugations (the reliable method for aging) requires microscopic views, several features lead me to believe the bird in question is a HY male. For starters, the bird had two red-gorget feathers on the throat which nearly always is a indicative of a HY male. Secondly, the head and body feathers were buff-edged which is associated with HY birds of this species at this time of year. 

Ruby-throated Hummingbird showing 2 red gorget feathers
Showing the buffy edged head feathers during preening

Generally speaking, caution should be employed in attributing age and sex to Ruby-throated Hummingbirds during late summer and fall via field observation. By October, the full red-gorgetted adult males have long left the state with most if not all birds falling into the nebulous female/hatch year category. While it is generally true, birds with minimal to no dusky markings on the throat are likely females this feature is not the sole determining factor for sex per my banding training with the Great Lakes HummerNet team led by Allen Chartier. Furthermore, while a few red gorget feathers often point to a bird being a HY male, Pyle notes in the Identification Guide to North AmericanBirds, occasional AHY females can have one to a few iridescent red feathers in the throat. Hence the waters of age and sex become quite muddy when observing this species in the field during late summer/fall.

Bill corrugations (wrinkles on bill) ~90% of bill in this example indicate HY bird

Throat pattern on a HY male RTHU
When banding, once age is determined by bill corrugations (wrinkles on the bill), for a HY bird sans the red gorget feathers, often the wing cord and culmen measurements are sufficient for determining sex. The males are shorter on both measurements. When these measurements fall in an overlap range between the sexes, the shape of primary 6 (p6) is used to determine the sex. On a HY male Ruby-throated Hummingbird, p6 is attenuated to sharp point and the outer vane is quite narrow. This is seen well in the digiscoped images I captured of my weekend visitor (see image below). However note in an AHY female, p6, though less pointed is quite similar. In contrast a HY female’s p6 is rounded at the tip with the outer vane being wider.

Attenuated p6 on my weekend visitor
Another characteristic to consider in separating HY males from HY females is the shape of the outer retrix (r5). HY males have a more tapered outer retrix.  In the absence of knowing he bird’s age, again there is overlap in the outer retrix shape of a HY male versus AHY female. Same goes for throat pattern. Not all HY males will have red gorget feathers and as noted above, some AHY females can actually have one to a few red gorget feathers. Hence the earlier caution stands, in the absence of knowing the age of a Ruby-throated hummingbird (most reliably determined by bill corrugations under magnification), Ruby-throated Hummingbirds that are not AHY males with full red gorgets should typically be left identified to species only in the field. However with careful observations and photographs one may be able to age and sex.

Somewhat attenuated outer retrix
Shape on the weekend visitor is consistent with HY male or AHY female
But back to my visitor which I’m calling a "he" since after handling a couple hundred Ruby-throated Hummingbirds this summer, I feel fairly confident this is a young male. He spends most of his down time in the Washington Hawthorne. It’s both close to some of the preferred feeders and is great cover with its 1-2 inch thorns that offer some protection against avian predators like the local Cooper’s Hawk. Though I’m not sure a Cooper’s would be satisfied with a measly hummingbird meal that is the equivalent weight of a penny.

Hanging out in the Washington Hawthorne


Washington Hawthorne
While others in Wisconsin report their hummingbirds preferring flowers and bugs over nectar feeders in recent days, mine fed consistently on the feeders all day Saturday. Infrequently I saw him foraging for insects in our large pine tree and once nectaring on the Turtle Head and Anise Hyssop.  


Despite the cold temps in the mid 30s the bird still mustered the energy on Saturday to chase away one of the resident Chickadees on several occasions.  It was nice to have this little distraction between chores when my desire to go out on some major birding foray in the cold damp weather was lacking. Time will tell if the little bugger will be here tomorrow.

I’m still holding out hope, with seven feeders cleaned and refreshed every 2-3 days, that a vagrant hummingbird will find its way to my yard this year!

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