Dear Martin,
I am sure that your bird at Bunyala is an immature Collared Pratincole.

I have attached a series of images….

Farthest left, your Bunyala bird

Towards the right are all Black-winged Pratincoles
Immature on ground, immature in flight (both South African wintering
birds) adult flight (Kuwait)

You can see that the amount of red on the bill of the immature BWP is
very much reduced compared to your individual.

An important feature of immature BWP is that they are colder grey
brown, not the warm rufous brown of Collared and your image.

If you had seen the bird in flight, you will see from the images of
both immature and adult BWP in flight, that there is no whitish
tipping to the secondaries unlike Collared.

This is close to the time when BWP could turn up at Bunyala, and even
though this is a Collared immature, you should keep an eye open for
cold greyer birds over the next month or so.

Now, do you have any images of the Mad Pratincoles that you say were
also there, as there have only been three records inland in the last
sixty years, and so this is as interesting as the BWP would have been,

Best for now
Brian