Thanks for your answer confirming that I'm (and well-intentioned friends) are overwatering. I'll just add that I'm pretty sure the soil is good as we shook a lot of it away when transplanted, and put in new soil. We perhaps did not put in enough of a drainage medium (only put a few stones around the drainage holes) so may try adding that. But a follow up: does that pot in the photo look big enough, or should I just do it over in a larger pot? Thank you.
I would kick it up a tad, with a larger container, preferably a clay pot (my preference anyway..) for they allow the plant to utilize what it needs for moisture and quickly disperse the rest through the container, whereas the plastic ones tend to hold the moisture on the root ball, which can be a problem. When you water, always remember to water until the water runs out the drainage holes, then back off until you notice the drainage holes beginning to dry out and then water again. I can't emphasize enough, the importance of the proper watering technique. I also think a soilless mixture would be better then the store bought soils, they don't compact like a soil will and cause problems with getting water and nutrients to the roots. A soilless mixture would consist of equal parts Sphagnum Peat Moss, Perlite, Vermiculite and shredded Bark..there is no nutrients in this mix, so you would provide fertilizer in granular form (a well balanced tropical/Palm mix) once every three months (about half a cup for your size Bird) and every 4th time you water, add a quart of soluble, like Miracle-Grow or Peters. Nick