 However , in a field study published in 1987 , researchers Cristina Ramo and Benjamin Busto found evidence of interbreeding in a population where the ranges of the scarlet and white ibises overlap along the coast and in the Llanos region of Colombia and Venezuela . They observed individuals of the two species mating and pairing , as well as hybrid ibises with pale orange plumage , or white plumage with occasional orange feathers ; their proposal that these birds be classified as a single species , has been followed by least one field guide . Hybrid ibises have also been recorded in Florida , where the scarlet ibis has been introduced into wild populations of American white ibis . Birds of intermediate to red plumage have persisted for generations . 
