Hi Nate,
You have been impressively busy, this is such a good haul of data,
thanks so much for all this input.
I don't know exactly how to drive eBird, so did not get to the
individual records themselves, but I did get into the images. For the
East African records they all fell into the March-November period
except, a bird on Mafia which could have a resident population like
Pemba.
When Don had his breeding record it was August which is when Mangrove
K's are in Kenya. On your detailed sighting list, the only record
outside of it was Doris's Tana records on 3rd and 4th Feb 2017, which
is interesting.
What I do find very intriguing is that when our birds are present, is
exactly the time they winter in KZN where they do not breed, which
certainly supports there being two different populations. When our
birds go south, so do the KZN birds to breed in the Eastern Cape. It's
dangerous to suppose anything in birds nowadays, but it would suggest
that our birds do not go as far south as Natal and are southern
Tanzanian and Mozambican birds.
Best for now
Brian