My 2 hens have pasty butts, why?

[JbR]

Depending on how big the lump is, it might dissolve with soaking the chicken's butt (or chickens' butts) in warm water. Massage it under water and see if it breaks up like a clot of mud would. If it's really caked in there, you might be better off snipping the affected feathers, poop and all. Shorter feathers would be less likely to collect the poop too. It really helps to have another person to assist with holding the bird.

Realize that since you are dealing with, um, poop, you will want to wear gloves and clean and sanitize the sink or wherever you soak the bird. (You also have to get over the "ick" factor, if this kind of thing grosses you out.) Go slow, be gentle. Read some threads about giving a bird a bath for more info on that part of it, and how to catch them, calm them down. Good luck! Let us know how it goes.

UPDATE
We gave both girls baths! It did turn out that the one whose behavior was more worrisome & the first egg layer (CL) had a stream of stuck excrement that had to be worked out slowly as you mentioned. I cut off a lot of it (very carefully), simply because it was a big chunk. Then worked out the rest with warm water & my fingers. The other girl (CH) had a relatively smaller amount of excrement, but more dirt/sand. They both did amazingly well!
They definitely were asking for calcium. Once I give them all they want they settle down... but CL is still acting panicky until I figure out what she wants that satisfies her... Maybe she just needs more because she has laid most of the eggs. Improvement is OK for now... I am carefully watching to see if she has loose stools. I'm also making sure her sister gets what she needs, since she's being pushy.
I am now sure both have started laying eggs though, which is Super exciting!

So far, thanks to all of the suggestions, I am relieved & hoping we are on our way to chicken happiness!

 

[Sally PB]

So glad to hear! Good work!