Hmmm... as someone with an interest in electronics, the only limitation here is the length of the wire connecting to the battery pack. If you were to extend the said wiring by supplementing it with your own, and relocate it to perhaps the side of the tree, etc. - and therefor to a place where you can charge it without disturbing them? Just three things to be aware of; this action would invalidate any warranty, make sure the battery is well protected from the rain as it would then be otherwise exposed, and lastly make sure any changed wiring is with correct polarity and guage and out of the reach of the birds!
I don't know how possible this would be, and other WAB'ers may dissagree. This is just a suggestion - get other opinions before deciding! (
Sorry, disclaimer time...

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