Black Redstart & Indian Robin, companions and territorial disputes

Every winter the Black Redstart spends his time at the Basunti gardens, which causes major territory battles with the resident Indian Robin. Both birds are of the same size and have similar habits and the disputes have therefore been intense.
Over the last few years they seem to have reached a status quo, where the Indian Robin occupies the lower half of the garden and the Black Redstart the top. A clear demarcation line seems to have been created where a line of ponds bisects the property. Both birds respect this situation and I never see either of them cross this agreed boundary.
Over the years they have become two of my favourite garden birds. Both of them are very tame and join me when I am working in their area. The Redstart even spends his nights roosting on my upstairs veranda. Lovely ‘house-share’ to have.