Thanks for all the nice comments. Looks like I need to work up the redpoll once I finish what is on the drafting table.
Phil, I think the outline/linocut look is just do to the way I build up the sketches and don't use an eraser very much. I almost always use a #4H or #6H pencil in a lead holder. I tend to work pretty quickly and very lightly at first. I make plenty of mistakes as I draw and just darken up the best line in the end. I'll keep most of the incorrect scribbles and just erase out the ones that are distracting. Leaving some of the other mistakes sometimes seems to give them a little more energy ... at least to my eye.
Colleen, to answer your Question about how to see all the detail. I pretty much use everything at my disposal to get the job done. Field sketches, museum specimens and, although this might be blasphemy to some here, I take a ton of photos. I seldom work form any one of these things, I combine all of them to get all the info I need for the details.
Photos have advantages and disadvantages. Gear is expensive and the learning curve is steep. On the other hand, you have a lot of detail if you get a good shot. Relying on any one photo can be problematic. Plumage varies, sometimes the pose is just off. That is where the field sketching has a huge advantage. You can work on a expressive pose which is dynamic. Museum specimens are great in that you can really see details of the feet, beak, and feathers, but I mostly look at study skins where there is just cotton stuffing in the eyes and the "pose" is non-existent. However, if you want to work on a painting of a ivory-billed woodpecker or labrador duck you can't be choosy.
In the end, I guess I just research it then pick and choose the information to paint from.