This quick depiction is an attempt to clarify how the tertials on these two juvenile Dowitchers differ. The first is similar to the Long-billed's tertial, i.e. the central area is consistently dark, while the second is supposed to resemble the Short-billed's tertial and shows lighter markings, if not exactly stripes, in the central part of the feather.
This discussion inspired me to wonder how all the wing feathers are arranged in a sitting bird. I had seen diagrams of feathers in flight, and the visible wing feathers on sitting birds, but I still could not picture where all the other wing feathers ended up.
My goal for the following diagrams is to communicate common concepts that I understand to be true for all birds. These sketches are not intended to represent all feather types or any specific bird species.
In the first figure, during flight, the coverts cover the connecting shafts of the larger flight feathers, kind of like shingles on a roof, to give the wing airflow integrity when extended.
I doubt that scapulars are considered wing feathers. They are attached to the body in the shoulder area, however, they cover a portion of the coverts so they do work together, kind of like good neighbors.
The second figure attempts to show the flight feathers beginning to slide under one another.
The most interesting part of the process is that the outermost primary feather, P10 in this example, ends up being the closest wing feather to the body when the bird is at rest. Immediately above, or outside, it will be P9, then P8, etc. This continues with the primaries being folded under the secondaries, and the outer secondaries under the inner ones, i.e. S1, under S2, which tucks under S3, and so on. Finally, the tertial feathers end up on top.
The bottomline is the positioning of flight feathers at rest, relative to the bird's body, is essentially precisely the opposite of their arrangement in flight. Depending on the bird, the tips of the longest primaries may or may not be exposed above the tail feathers when at rest.
A trusted source for this information is an excellent write up by David Sibley's in Bird Watching. Click Here to read it for yourself.
As Marcus pointed out to me, the ultimate result is that the majority of the critically important primary feathers have the greatest protection from UV light when the wing feathers are fully tucked away.
Another rule of thumb to use when identifying Dowitchers is that Short-billed Dowitchers are more likely to be seen in Salt-water environments i.e. surrounded by Salt. Long-billed Dowitchers are more likely to be found in fresh-water environments that are usually surrounded by Land. I use the S in salt and the L in land as mental reminders of these associations.
However, the photo from the mouth of the Cedar River, shows both species standing side-by-side in freshwater. This demonstrates that location is not a precise method of identification, and explains why the birders were still looking for "tiger stripes".
Another helpful method of identification is to listen to the different sounds that two species make.
Click Here to hear the higher-pitched sounds of a Long-billed Dowitcher on All About Birds.
Click Here to hear the lower-pitched sounds of a Short-billed Dowitcher on All About Birds.
In case you are wondering, Yes, I was disappointed to realize that the Short-billed makes the longer sounds waves and the Long-billed makes the shorter sound waves. 🤷 The opposite sure would have made a great memory aid.
On a more positive note, I believe Marcus identified every shorebird within sight or sound near the mouth of the Cedar River. I am lucky to be able to share the link to his eBird checklist from that day. It includes his very instructive commentary and Sandy Pringle's excellent photos. Thank you, both!
Click on the following link to enjoy: