Questions

A small colony of ants have appeared all over the waste matter in my compost bin; are they a threat to the process or final compost?

My four Cordyline Trees, despite their not unattractive appearance, are 15 foot high and a maintenance burden with their constant shedding of numerous long leaves and seperate flowering panicles attracting hosts of starlings with resultant nuisance. Can they be coppiced or shortened to half their height, if so would they survive or should I remove them permanently.