Friday, January 18, 2013

That "Documentation" Thing

During a recent exchange with Mary Nemecek, we stumbled onto the topic of written bird descriptions. The general question was just how long of a description can one manage when compiling a written documentation? Well, maybe that wasn't really Mary's question, but she did indicate that it might be useful to her to take a peek at what happens when Kristi Mayo sits down to document a rare bird.

So, in the interest of helping Mary and probably frightening many others, what follows is possibly the longest documentation known to man ... or, at least, the longest one I could find in a quick search of my records.

Back in September 2010, I crossed paths with a very rare and difficult-to-identify bird. Well, it was difficult for me to identify, at least. The process of identifying that bird is well documented in this previous blog entry. The situation was unique, because at the time, I had done very little reading on jaeger identification. I didn't know what details were important and what details were irrelevant to the identification of an immature jaeger. So, from the outset, I aimed to make notes before delving into the field guides. The result was probably one of the most un-biased set of field notes I have ever compiled.

After the dust had settled and I was confident that Long-tailed Jaeger was the correct identification, I had to sit down and submit my written documentation—along with a detailed set of photographs and video—to the Missouri Bird Records Committee (MBRC). When writing my description, I tried to include useful details such as:

- size, especially in comparison to nearby known species
- structure
- behavior
- general impression

...and, of course, a careful description of the bird. When writing a description, I try to walk the reader through the bird from head to tail and from bill to legs. In the case of a complex identification such as a jaeger, I was extremely thorough; in a less difficult identification—or, admittedly, one I wasn't so darn excited about—my description might not be so long. Since I had multiple observations of this bird, each at different distances, I was careful to report my impressions at each range. The impression at 1/2 mile can be just as important as the impression of a bird in the hand.

Did I really need to write the (possibly) longest written doc known to man? After all, there were lots of pictures taken of this bird, and it was seen by many observers. So no, I probably didn't need to write this much in order for it be accepted by the MBRC. But, it was good practice, because we're not that lucky in every observation. Sometimes you see a bird only for a few moments, and a photograph isn't possible. Or maybe the photograph is fuzzy. Maybe the photo doesn't show key details like the spread wing, the rump, or the lores. The more thorough your written documentation becomes, the more likely you are to include the key details that will confirm your identification, with or without photographic support. And, the more you scribble those field notes and strive to throughly scrutinize that avian rarity before diving into your field guides—Oh! it's so tempting to go to the books first!—the more you are going to learn.

Description of the Bird

This bird was first observed on 16 September 2010 at about 17:00. It was in flight at a long distance (1/2 mile) for the vast majority of that observation. On 17 September, I returned and watched the bird almost continuously through my scope for two hours, this time having my best views when the bird sat down on the water and preened at a distance of about 400 yards. On 19 September, I rented a boat and captured photographs within 30 yards. On 20 September, on a scheduled boat tour of the lake with Burroughs Audubon Society members, we were able to get the bird within 10 or 20 feet of the boats, and at one point it was within an arm’s length from me.
Gull-like bird. In direct comparison to Ring-billed Gulls at close range (10 feet), the bird was lighter in structure and slightly smaller. With indirect comparison, it seemed similar in size to a Franklin’s Gull (which came near the boat just before and after the jaeger). Also seen at a distance (1/2 mile) in direct comparison to Sabine’s Gull (Sabine’s Gull appeared to be smaller than the jaeger) and Osprey (Osprey’s wingspan appeared less than twice as long as the jaeger).
Flight varied from slow flaps and glides, soaring and circling on thermals for long periods of time, and then folding wings to drop quickly to lower altitude, then accelerating in a more direct, powerful flight when pursuing other birds. At a distance, flight struck me as being falcon-like, not particularly buoyant, but overall very similar to a gull’s familiar movement. Wings backswept. An aerodynamic appearance, fairly deep-chested, tapering to a long tail, with the body and tail’s projection behind the wings being about twice the length of the head’s projection in front of the wings.
Even at 400 yards, the head appeared small, with a dove-headed appearance, and large dark eye. Bill small, bluish gray base with black tip. At close range (10 feet), the black at the tip bleeds down the cutting edge of the mandibles. Black tip about 1/2 the length of the bill. The actual nail was shorter than the total of the black tip, about 1/3 the length of the bill. Nostril, positioned behind the nail and gonys, was approximately at the center of the bill, with the back end of the nostril being closer to the base of the bill than the tip of the bill. Fairly shallow gonydeal angle. At 400 yards, face appeared very pale buff with pale buff above eye and around base of bill. Darker, grayish buff on forehead and top of head, forming a slightly “capped” appearance. Nape pale buff. At close range, faint streaking on face, nape, and neck.
Lower neck and upper breast clean grayish buff with some reddish-brown tones detected when in flight (less noticeable in direct, intense sunlight). Darker breast band very obvious in flight and at a distance, cleanly separating the pale buff head from the pale buff sides and belly. Snow-white base to feathers (exposed when preening). Sides barred with grayish-buff barring, relatively indistinct and difficult to see at a distance and at certain angles. Clean, black-and-white barring on flanks, undertail, and rump. 
Back contrasts with head and underparts. Dark brown or blackish (at a distance). At close range, each feather on the back and wings neatly tipped with pale, grayish-buff edges that are similar in tone to the face and breast. At a distance (400 yards), this gives a paler appearance to the coverts and scapulars, which contrast with the darker primaries and secondaries. Pale edging to the greater coverts creates, at a distance, the appearance of a pale line or very narrow bar that runs the length of the wing. Front edge of the wing has a crisp, pale, line, usually only apparent when the bird is viewed head-on in flight. Primaries 10, 9, and 8 with a pale shaft. My notes from 17 September show that at a distance of 400 yards, the pale shaft was only apparent on P10 and 9 (observed in flight and while preening). Underwing neatly barred and marbled black and white, similar in tone to the barring on the flanks and tail coverts. Pale base to the primaries created a variable white patch on the underside of the wing, which seemed more pronounced at a distance and changed in intensity depending on the bend and action of the wing. 
Tail dark brown or black, rounded. Two central rectrices project noticeably beyond the rest of the tail. At a distance, the shape of the feathers were seen very well when the bird preened its tail. Central rectrices rounded at the ends. At close range, the tips of the rectrices were edged in white. 
Legs and feet (observed at very close range) pink with black webbing, giving the appearance of having been dipped in ink. 
Behavior: Incredibly fast flyer, capable of covering the entire distance of the lake in just a minute or two. Almost always flying very high, about 1.5 binocular views above the trees. Observed pursuing several Osprey, Ring-billed Gulls, and a juvenile Sabine’s Gull. The bird would dive on its target, sometimes pursuing it for a short distance. Harassment of other species did not last very long—perhaps 30 seconds at a time—and chases were never successful. Once, the bird dropped from a high altitude and sat on the water, picking at a fish that had apparently been spotted floating on the top of the water. At 9:45 a.m. on 17 September—presumably at the time of day when thermals begin to rise higher—the jaeger circled to a very high altitude and soared around making short, acrobatic movements and flicking its head—possibly catching insects—much like a Franklin’s Gull. On 20 September, the bird came within feet of a pontoon boat full of birders, eating popcorn that had been thrown out on the water.

Similar Species Discussion

First, this bird was aged as a juvenile by the presence of extremely clean, crisp, pale edging to all feathers (including primaries and tail).Juvenile Pomarine Jaeger was eliminated by size (this bird was the same size or smaller than a Ring-billed Gull, while Pomarine would be the same size or larger); the pale, grayish-buff edges to feathers and overall cold, grayish appearance (while Pomarine would tend to be darker and have warm, golden-buff edges to feathers); a “sweet”, small-billed look to the head (while Pomarine would be heavier billed with stronger gonydeal angle); the notably longer central rectrices (while Pomarine has a less-pronounced projection in the central rectrices); and the lack of any distinct white ?flash? on the underwing, where Pomarine has extensive white bases to the primaries that would be much more noticeable even at a distance. Juvenile Parasitic Jaeger was eliminated most definitively by excellent looks and images of the bill. The black in the bill extends to nearly 1/2 the total length of the bill, while Parasitic would show a black tip about 1/3 the length of the bill. The nostril is positioned at about the center-line of the bill, with the distance from the tip of the bill to the nostril being greater than the distance from the nostril to the base of the bill. In Parasitic, the nostril is positioned closer to the tip of the bill than the base of the bill. Additionally, in flight, this bird was broadest at the breast, tapering quickly to the tail, while Parasitic would appear more “pot-bellied” in flight. Parasitic tends to be darker with golden-buff edges to feathers. Parasitic shows a stronger white “flash” on the underwing and sometimes the upperwing, while this bird showed only a faint pale area on the underwing at certain angles. The two central rectrices were rounded, while Parasitic would have pointed central rectrices. Barring on the flanks of the Parasitic is less distinct and more uneven, compared to the very neat vertical, black-and-white barring of this bird. Parastic has 3-8 pale primary shafts, while this bird had 3 (only 2 visible at >400 yards).

Resources Used / Did they affect they way you wrote?

Sibley Guide to Birds (Sibley); Advanced Birding (Kaufman); Skuas and Jaegers (Olsen and Larsson); No—Documentation above is based largely on field notes take during a lengthy but distant observation on 17 Sept, prior to doing any in-depth reading or study. Documentation modified 25 September to include details observed at much closer range on 20 September.

1 comment:

Doug said...

Well done Kristi! I'm still trying to find the balance between field notes vs. digiscoped photos when a rare bird is encountered. Difficult to do both simultaneously and I shudder to think of the detail I miss while fumbling with camera, scope and the subsequent "chimping!"