first pic: 2 juveniles, so bill colour not usefull; 6 fingers, not usefull as only if 5 we have a sure Yellow-billed, but quite a few show 6 fingers; plumage-wise identical or near so; only feature left is freshness of plumage and moult: these two have very fresh plumage unlike Black Kite in February, so 2 juvenile Yellow-billed.
Pic 2: second year Yellow-billed, just a few juvenile feathers left and bill only with black tip
I expect Tom is correct - but although I have little experience with aegyptius (lots with migrans) I have questions ( of course !). I have no experience of parasitus (I’m assuming in Ethiopia it would the South African race, parasitus?).
The first 2 seem to show several 2cy/juvenile migrans features to me - (I know we have overlap, but there are several features that stick out to me)
I wouldn’t normally associate these really obvious dark ear-coverts with a aegyptius/parasitus (or perhaps it is so in 2cy?) and such a shallow tail
The bare parts in the first birds look very bright to me (the very black shiny bill contrasting so much with bright yellow cere) - is that so good for any age aegyptius/parasitus? I would prefer that for 2cy juve plumage migrans only and expect a greyer, duller bill with a more ‘dirty‘ less contrasty yellow cere in this age group for YBK (which of course gets more yellow and less black with age)
Juvenile migrans do have a post-juvenile body moult on their winter grounds so would look still quite fresh in February. Don’t the primaries look a little worn/faded brown in the first image?
I am happy with the bird the second image being a YBK (because I can’t see the features I am questioning in the first) - but not sure on the 100% YBK for the first two.
BTW they would all be 2cy birds if taken in February. Or are you saying you think the second image is a 3cy bird?
I fully agree that juvenile of both species are really hard to ID, especially when wing formula is of no help as here.
I do not think that Yellow-billed juvenile has less bright yellow cere than Black Kite
As to the first winter moult in Black Kite I would indeed expect Black Kites showing quite a bit of new body feathers and coverts, but these are all first generation
Tail might look better for Black but not really helpfull in juveniles as here I'm afraid.
Still happy to be proven wrong, any pictures of upperside maybe?