This image contains both Red-billed Quelea (Quelea quelea) and Cardinal Quelea (Quelea cardinalis) -both in non-breeding plumage.
A typical male Red-billed Quelea is at top right and a typical female Red-billed Quelea is at bottom left -the faded black mask of the male is still clearly visible whilst the large red bill is apparent in both (immatures have a brownish-pink bill).
After breeding Cardinal Queleas are hard to sex as both have a yellowish chest wash though often there is some residual red on the head or throat as on the bird on the lower right which retains a thin reddish "necklace". Immature Cardinal Queleas have a pale brownish chest but all sexes and ages have a dark brown bill.