Q is for Quill.
The bare part of the central shaft of a feather, nearest to the body. As the true feathers start to grow in youngsters, the feather is surrounded by a sheath and has a regular blood supply.
When these ‘pins’ as they are known, continue to grow, they are very vulnerable. They will bleed a lot if damaged, so it is good practice to reduce catching up birds at this time (this teal was expertly handled at a teaching facility). You’ll hear people referring to them being in ‘blood feather’, it’s really good description.