In 1987, the British ecologist Anthony S. Cheke proposed that the last two types mentioned were male and female Newton's parakeets, and that the differences between them were due to sexual dimorphism. The last bird mentioned had earlier been identified as introduced grey-headed lovebirds ("Agapornis canus") by A. Newton, but Cheke did not find this likely, as their beaks are grey. Pingré also mentioned green birds, perhaps with some red colours, but his account is partially unintelligible and therefore ambiguous. A red shoulder patch is also present on the related Alexandrine parakeet. None of the existing Newton's parakeet specimens have red patches. The single known male specimen may have been immature, judged on the colour of its beak, and this may also explain the absence of the red patch. When "Psittacula" are bred by aviculturalists, blue is easily produced from green; the production of blue may suppress red colouration, so blue morphs may have lacked the red patch.