Weird lump on Base of tail

[sooty and sweep]

HI today I Noticed a lump on sooty who is about 1 1/2 years old. It is on the Base of the tail( see pics). She has also been shaking and preening aroud that area.I saw it when I was checking her as my other hen sweep is bein a lethargic on my other thread.
Other wise everything is normal
Thanks Finn

 

[rebrascora]

Not seeing any photos but I'm wondering if it is her preen gland which is situated on the top side of the tail about an inch from the end. It would explain why she is preening around it. The preen gland provides the oil to preen the feathers with to make them water repellent, so they keep going back to it to get more oil to work into feathers in other places. If you google preen gland you should find images that will either confirm that's what it is or rule it out.

 

[smudge]

I'd second the preening gland... And also see no photos.