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A BILL-DAMAGED HUMMINGBIRD

Now that essentially all those Ruby-throated Hummingbirds that bred in the U.S. and Canada have bailed out to Mexico or Central America for the winter, our hummingbird banding activities have essentially halted at Hilton Pond Center. At the same time, our banding has expanded geographically to include winter hummers showing up in the Carolinas in record numbers over the past decade. Thus, when we heard from Susan Holland on 26 October that a new hummingbird was visiting her feeder at River Hills in northern York County SC, we wondered what sort of vagrant species it might be. Susan, a longtime birding friend and regular participant in the York/Rock Hill Christmas Bird Count, called it a female Ruby-throated Hummingbird from the very beginning, but since our latest-ever date for a ruby-throat at Hilton Pond is 17 October, we wondered if it might not be a female (or young male) Black-chinned Hummingbird--a western species that occasionally shows up during winter in the eastern U.S. The only way to get a definitive answer, of course, was to visit Susan's house with our portable hummingbird trap, which we arranged to do before dawn on 28 October.

We arrived at Susan's house on a dark and foggy Thursday morning, set up the trap, and waited for the bird to enter. It zoomed through a couple of times in the twilight but showed no interest in feeding within the trap, preferring instead to dine on Red and Pineapple Sage plants on Susan's deck and in her backyard--and at a second feeder some distance from the house. After waiting almost three hours and observing the bird only twice or thrice, we decided to shut down the trap and return another day--with the intent of taking down the second feeder to eliminate competition for the bird's attention.

On 29 October we again showed up pre-dawn, removed the second feeder, set the trap, and sat back to wait. The bird appeared almost immediately but did not enter the trap; this time, however, it at least perched on overhead branches rather than making a bee-line for points unknown. Despite its proximity to our viewing position, it still wasn't possible to determine the bird's species. Eventually the hummer flew away, returning at about 8:45 a.m. when it entered the trap but exited immediately before we had time to hit the trigger on our remote release. Fortunately, the bird came back within half an hour, re-entered the trap, and began feeding. This time we were ready, and Susan Holland's bird was snared as the sliding trapdoor closed behind it.

As we approached the trap we still didn't know for certain what kind of hummer we had caught, but we saw pretty quickly that it was not a normal hummingbird. Halfway along its upper bill (top photo) was a pinkish-orange bump so large it would have prevented the bird from inserting its bill all the way into a port on most plastic hummingbird feeders.

Finding hummingbirds with bumps on their bills isn't an unheard-of occurrence. We've rarely seen the phenomenon on summer ruby-throats, but on several occasions we've trapped winter hummers with bumps. We've never known exactly the cause. Perhaps some winter birds manage to find forgotten feeders containing badly spoiled sugar water that causes mold to grow on the bird's beak. Or maybe bumps on bills in winter birds means there is something else wrong--something that might somehow alter a bird's normal migration and wintering patterns and cause it to show up well away from its normal range. More likely the bill bump is simply a birth defect or the aftermath of an injury.

Based on measurements and the shape of the primary feathers, we determined Susan Holland's bird was indeed a female Ruby-throated Hummingbird, but we couldn't be sure of its age because of the extensive damage to its bill. (Ruby-throats are typically aged by looking for tiny etchings on the bill; these are present in juveniles but disappear in adults.) However, since there was also a bump on its lower bill, we suspect the bird had flown into a stationary object that fractured the entire bill.

The top bump itself was soft tissue that was growing erratically without the restraint of the hard, black bill sheath that normally would cover it. Apparently the bird's repair system was attempting to fix the break--which was quite flexible at the joint--but this injury was so extensive it didn't seem like it could ever become fully healed.

It's possible the break was older than the fresh, raw wound that it appeared to be. We base this supposition on the fact that the lower bill was two millimeters longer than the upper, and that the tips of the bill halves crossed slightly; we suspect it would have taken several weeks or months for such differential growth to occur. We have seen differential bill growth before, as in a Ruby-throated Hummingbird we banded one summer at Hilton Pond (above left). This particular bird also appeared to have run into something and broken off its upper bill, but in this case the damaged part was far enough forward that it healed over, and the bird fed normally at flowers. The lower bill, however, got thicker and wider, forming almost into a narrow spoon or spatula so that this bird was unable to insert its knobby bill tip into a feeder port.

Connie Sale, a wildlife rehabilitator in Virginia, has treated several bill-injured hummers and learned that the bills can grow back if the injury is confined to the outer third of the bill and if the bird is provided with good nutrition. According to Connie, damaged hummingbird bills sometimes go through a "granulomatous" stage in which very friable tissue (that bleeds a lot) is visible; this is what shows in the top photo of Susan Holland's bird.

Sometimes injured bills do NOT become granulomatous and grow back smooth and "normal." This appears to be the case with a bump-billed winter female Rufous Hummingbird we banded in February 2001--her upper bill overhung the lower by 2mm and gave the bird a hook-billed appearance (above right and below). Such injuries may have little impact on healed hummingbirds; the Casar bird returned in November 2001, was recaptured and released, and spent the whole winter.

Since Susan Holland's bird was able to stick its tongue out far enough to lap up sugar water from a feeder port, it, too, may be a survivor. We'll never know for sure, however, since Susan never saw the bird again after we banded it. Perhaps this aberrational hummer was finally en route to its wintering grounds south of the border, or maybe it simply departed to look for even easier pickings in the Carolina Piedmont. Who knows? Susan's home is only 15 miles away as the Ruby-throated Hummingbird flies, so maybe her hummer will even show up here at Hilton Pond Center in some future year with a big, black bump that demonstrates the remarkable healing abilities of bill-damaged hummingbirds.

All text & photos © Hilton Pond Center

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SPECIES BANDED THIS WEEK:
Carolina Chickadee--2
Black-throated Green Warbler--1 *

* = New species for 2004

WEEKLY BANDING TOTAL
2 species
3 individuals

YEARLY BANDING TOTAL
(2004)
62 species
1,828 individuals

BANDING GRAND TOTAL
(since 28 June 1982)
123 species
45,133 individuals