Forpus coelestis: Yellam green

Forpus coelestis: Yellam green

By Dirk Van den Abeele

Ornitho-Genetics VZW
MUTAVI, Research & Advice group

It was at the end of 1980 when in the USA an ‘almost yellow’ Forpus coelestis was born [1].  The fact that this new mutation had dark eyes, could immediately exclude the possibility of an ino form.   With an ino mutation, it is typically that besides a visual reduction of the eumelanine presence (the dark pigment in the feathers), resulting in a yellow bird, thus the eyes can also not have the normal dark colour, but they are red coloured [2, p. 345].  Not only these red eyes are absent with this mutation, also the body colour is not yellow like a ino is, but is generally described as ‘light yellowgreen’.

Analogically with the approaches of colour mutations in those times, the bird was named ‘American yellow’.  American referred naturally to the place of origin and the name yellow was speaking for itself.

When the international directions for naming colour mutations were introduced in 1999, one of the rules was that no proper nouns or names of locations could be part of the name [2, p. 244], [3, p. 100].  Thus we had to search for a suitable name.  Naturally, one cannot randomly stick a name to a phenotype, first of all we have to try to find our whether this mutation is already existing, and in case it is, we have to take over this existing name.  But that appeared not to be so easy.  There was rather a long list of options.

The first idea what crossed the mind of many breeders was pastel.  Pastel is an autosomal recessive mutation, which causes a visual reduction of about 50% of the eumelanin and, important, it is an allele from the NSL ino locus.  The reduction we observed with this mutation, did not quite fit in the frame of 50% visual reduction, but nonetheless several of these birds were paired with available NSL ino mutant birds of Forpus coelestis.  If this mutation is really an allele of NSL ino, the offspring had to show an intermediate colour, but that proved not to be the case.  So we could exclude pastel, as well as all the other mutations from the NSL ino locus.  In other words, it was also not a dark eyed clear (dec) or what breeders sometimes use to call blackeyed yellow.   Meanwhile, at our request a lot of test matings were made by eleven breeders worldwide and registered with us.  Not one of these outcomes sorted something out.  Meanwhile, names like dilute, suffused, pastel etc. are circulating.  We always advised to just use the name *US yellow*, placed between asterisks though, it indicate that this was not yet a definite name, until we had found out more information about the mutation.  Unfortunately, some people don’t care about this and thus cause a lot of confusion.

Meanwhile, at MUTAVI, Research & Advice Group, a lot of feathers from these birds were being examined.  We didn’t just examine feathers from birds coming from European collections, but also from the United States.  Just as a matter of having certainty that we had the right feathers available.  But even this research made anything clear.

An option we also had in our mind since the beginning, was the fact that this mutation is a type of dilute.  With dilute, we have a mutation of the Myosine Va locus [4, p. 171], [5] where the formed eumelanin gets damaged during the transport of the pigments in the feather.  This results in typical macromelanosomes in the feathers (very big clutching of the present eumelanine).  Unfortunately we didn’t retrieve these in the feathering, except in one single feather where Inte Onsman found a (small) macromelanosome.  Naturally, one bird doesn’t bring spring time and it is not yet prove that we really have to do with a type of dilute.  If it is really the case, it will probably be an extreme –still unknown- allele of this gene.  The only way to test this correctly, will be when a real dilute mutation occurs with Forpus coelestis, this dilute to pair with this mutation.  When we then will get an intermediate form, prove has been delivered.  But as long as we don’t have dilute with Forpus coelestis, thus far we can only guess.

Meanwhile, we were not resting but we compared the eumelanin of this mutation with different kinds of other mutations.  Unfortunately, we never found a match somewhere.  So we had to search through other channels and numerous researchers were asked about their opinion.  Unfortunately not a single match was found with any other existing mutations.  The cautious conclusion would be that it is probably a not yet described mutation.

As from aviculture, we kept receiving questions for a suitable name, we have considered a few appropriate possibilities.  One of the rules is that the name for a mutation is preferably in English or that it is an unique term.  Besides a number of suggestions from the existing list of possible (English) names, I also tinkered a little with the syllables of the original name American yellow.  Amyel, seemed to be already an existing name, so I decided to suggest also yellam on it.  This term has actually no meaning in English, but refers nonetheless to the original name.  Different naming options were presented to a number of breeders – hobbyists – judges and strange but true, they all preferred the name yellam.

Naturally, we always respect these choices and thus we propose the name yellam for this mutation.  In the green series we thus speak about yellam green, in blueseries of yellam blue and combined with turquoise of yellam turquoise.

Thus far, we keep the genetic symbol ‘ya’.  Eventually if later this mutations proves to be an allele of dilute or another gene, we will naturally adapt this symbol.

Yellam inherits autosomal recessive.  With pairings, this can result in the following options:

Green x yellam green:
100% green/yellam

Green/yellam x green:
50% probability of green
50% probability of green/yellam

Green/yellam x green/yellam:
25% probability of green
50% probability of green/yellam
25% probability of yellam green

I want to note here that the homozygote green youngsters are in principle not visually distinguishable from the split youngsters.

Green/yellam x yellam green:
50% probability of green/yellam
50% probability of yellam green

Yellam green x yellam green:
100% yellam green

Good luck with your yellams!!



  1. Balaban,  “Breeding Yellow Mutation Parrotlets”, Bird Breeders Magazine, 1997.
  2. Van den Abeele, Lovebirds Compendium, 1st pr. Warffum- The Netherlands: About Pets, 2016.
  3. Van den Abeele, Erfelijkheid bij vogels, 1st pr. Welzo media, 2015.
  4. Lynn M Lamoureux, V. Delmas, L. Larue, en D. . Bennett, The Colors of Mice A Model Genetic Network, 1st dr. London: Wiley-Blackwell, 2010.
  5. C. Bridgman, “Myosin Va movements in normal and dilute-lethal axons provide support for a dual filament motor complex”, J. Cell Biol., vol. 146, nr. 5, pp. 1045–1060, 1999.