SCARLET MACAW (ARA MACAO) - GENETICS

NEW EXCITING SCIENTIFIC STUDY:

Genetic evidence for only two different subspecies

An impressive Ara macao cyanopterus, adult bird, sitting ready to take off from a piece of rock.

Introduction

Among the large Central and South American Macaws, the Scarlet Macaw (Ara macao) has over the years become my absolute favorite, especially when it comes to the subspecies, Ara macao cyanopterus (formerly known as Ara macao cyanoptera), in English known as the Northern Scarlet Macaw (or the Central American Scarlet Macaw or even the Nicaraguan Scarlet Macaw among several other designations). When you look at this subspecies in top condition and with a perfect plumage, its beauty is beyond compare. In my opinion, no other large Macaw species is able to match these charismatic birds due to their absolute beautiful and sharply demarcated, extremely colourful plumage. Moreover, it is my experience that they are a bit gentler and calmer compared to some of the other large Macaw species.

The Scarlet Macaw was first described by the great Swedish taxonomist and zoologist (etc.), Carl Linnaeus, back in 1758 as Psittacus macao, later Ara macao, and it was for more than two centuries considered a monotypic species.

However, in 1994 the American scientist - today Senior Conservation Scientist at American Bird Conservancy, Virginia, US - Mr. David Wiedenfeld, discovered and described Ara macao cyanopterus (from Central America) as a new subspecies. This discovery has been acknowledged by leading societies for natural science, museums, institutions, etc. David Wiedenfeld conducted his scientific study based on four morphometric traits/measurements (upper mandible length, lower mandible length, longest toe length and wing chord-length) and on plumage variation among 31 museum specimens of known geographical origin, and his work led to the division into two subspecies. Ranging from southern Mexico to central Nicaragua Ara macao cyanopterus is considered as bigger and more robust, with a wide band of yellow on the median and secondary wing coverts and general absence of green feathers in the plumage. Populations distributed from southern Nicaragua to Brazil are classified as Ara macao macao (with the status as nominate subspecies) and are identified by reduced yellow areas on the wings and more pronounced green colouration in wing feathers, as well as overall smaller size. David Wiedenfeld also observed a steep decline in wing chord-length and intergradation of colour variants in southern Nicaragua and northern Costa Rica, designating this area as a natural hybrid zone between Ara macao cyanopterus and Ara macao macao.

When reading this article, please be aware of the following:

A wild Ara macao cyanopterus sits outside of a rescue center for Macaws in the small town of Mabita, Honduras (Photo: Art Howard / Christi Lowe Productions).

As I wanted to learn more about the characteristics of Ara macao cyanopterus from a scientific perspective, I started a dialogue with Mr. David Wiedenfeld, who was very helpful in relation to my many questions. He also drew my attention to a ­- to me completely unknown - new (late 2019) comprehensive scientific study of the Scarlet Macaw (Ara macao) seen from a genetically point of view. This new - technically very complicated - study made by a research team of scientists (Kari L. Schmidt et al.) from Colombia University, American Museum of Natural History and Montclair State University, has clearly substantiated David Weidenfeld’s discovery from 1994 of a new subspecies, this time based on genetic material from 100 Scarlet Macaw samples of birds distributed across the majority of the species’ historical range. This is the newest, most comprehensive and detailed genetic scientific study ever conducted of the Scarlet Macaw. The study was published in 2019 in "IBIS - International Journal of Avian Science", which is run by the British Ornithologists' Union. Founded in 1858, the British Ornithologists' Union is one of the world’s oldest and most respected ornithological organizations with an international membership stretching across all continents.

Before I share some of the key findings from this new genetic study with other serious aviculturists for whom aviculture is not only a hobby, but a passion based on an approximate scientific approach, I would like to emphasize our responsibility as serious aviculturists. We as aviculturists - and not at least as breeders - can make a noticeable difference by purposefully preserve these rare and beautiful birds in human care (“captivity”). As a serious aviculturist it is of greatest importance in details to know the difference between the two subspecies and to keep them apart from each other and breed them separately. It is only up in recent times, that aviculturists have become really aware of the two different species. Unfortunately, many aviculturists still don’t know the difference, and it has in an unhappy way led to breeding of numerous cross-bred birds between the two subspecies in human care over the years. If we - the serious aviculturists - don’t act responsible, it will inevitably soon lead to the annihilation of the latest discovered subspecies, Ara macao cyanopterus, in human care. We must take good care of those pure birds we already have, as we no longer can get birds from nature. And who knows, over time, we aviculturists may also be able to get our Scarlet Macaws “subspecies determined” based on genetic analysis as we already know from other non-monotypic parrot genera. In addition, the Ara macao cyanopterus has in recent years faced a number of immediate threats in the wild, partly in the form of destruction of its natural habitats and its nesting opportunities, and partly as a result of persistent capture for use as pets.

Ara macao cyanopterus, a few months old vital bird with a wide band of yellow and general absence of green plumage on the median and secondary wing coverts. If you keep two or more of these young birds together, make sure that they are continuously stimulated and employed. You should therefore give them lots of new fresh branches and twigs (must not be contaminated and not exposed to pesticides), as they at times may find themselves entertained by biting each other in their very long tails. The tip of the tail may, by virtue of the length of the tail, have a tendency to bend downwards.

And now to the new study:

The purpose of the new study

Many people - not least aviculturists - have over the years believed that several different kinds of Scarlet Macaws (Ara macao) exist due to differences in size and in the colouration of the plumage. More - including authors of books on Macaws - have, without having any scientific evidence, made descriptions of the, in their opinion, several types of Scarlet Macaws (Ara macao) that exist. Until now, these authors and others haven’t had the scientific basis to make credible statements about this subject, but it is something that this new study now is changing. Therefore, this new study is extremely interesting for serious aviculturists.

Scarlet Macaws (Ara macao) have the largest geographical distribution of any Neotropical parrots and occur widely across different habitat types (primary a variety of lowland forest habitats) from Mexico to Bolivia and eastern Brazil. According to BirdLife International the extent of occurrence (breeding/resident) for the species as a whole is estimated to 10,200,000 km2. Therefore, there is good reason to suppose that this species also is characterized by a number of differences in terms of variances. Hence the new study aimed to investigate the extent of genetic diversification within Ara macao by analyzing mtDNA sequence data (mitochondrial DNA, the part of the DNA producing energy, and it differs from other DNA, since it is only inherited from the mother like in most multicellular organisms) from present and historical samples of known geographical origin.

The fact that mitochondrial DNA only is maternally inherited, enables genealogical researchers to trace maternal lineages far back in time. Thus, the evolutionary aspect of the Scarlet Macaw throughout the ages has also been the focus of this study.

Ara macao cyanopterus, a few months old bird. On this bird you can also observe a wide band of yellow and general absence of green plumage on the median and secondary wing coverts; note that the tips of the secondary wing coverts are blue, there are no green feathers at all. According to Mr. David Wiedenfeld who discovered the new subspecies, Ara macao cyanopterus, this is described as having little to no green colouration, whereas Ara macao macao exhibits small to substantial amounts of green plumage, with no empirical means to quantify “little” versus “small”.

Analytical methods

The research team used a number of widely recognized and well-proven scientific tools, methods and processes in order to obtain a solid and well-founded genetic analysis material to provide a credible and secure research result.

Genetic material (samples) from 100 different Scarlet Macaws distributed across the majority of the species’ very wide range was obtained. DNA was also extracted from feather, blood or tissue collected from wild individuals in Guatemala and Belize.

A partner (University of Idaho, US) provided DNA-extracts from feathers acquired along clay licks in the Tambopata National Reserve, Peru, which is a well-known territory for Macaws, Amazons and several other parrot species. The remaining tissues were toe-pads taken from study skins located among natural history museums from all over the USA and handled according to formal processes.

Without addressing it further, it may be mentioned that DNA was amplified (repeatedly copying a piece of DNA) and sequenced at four mitochondrial gene regions. DNA sequencing is the process of determining the nucleic acid sequence- the order of nucleotides in DNA.

The practice of reconstructing the evolutionary history of related species by grouping them in successively more inclusive sets based on shared ancestry, called phylogenetic inference analysis, was also used. Actually, two different methods of phylogenetic inference were used to evaluate hierarchical relationships among haplotypes, maximum likelihood (ML) and Bayesian inference (BI). Haplotypes are a group of alleles in an organism that are inherited together from a single parent, and alleles are each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

The research team furthermore used population aggregation analysis to uncover the current hypothesis of intraspecific diversity in Scarlet Macaws.

Corrected genetic distances were calculated among each aggregated population identified in the study using four different genetic regions (mentioned above) to further investigate patterns of intraspecific genetic variation.

To assess further taxonomic distinctiveness and evaluate the extent of divergence between Ara macao cyanopterus and Ara macao macao, the research team succeeded with sequencing a complete mitochondrial genome from each subspecies (genome is a complete set of genes for an organism).

After the study all the uncovered DNA-sequences were deposited in GenBank®,which is an international genetic sequence database containing an enormous collection of all publicly available DNA sequences worldwide.

Some results

During the new study 70 haplotypes were detected among concatenated mtDNA sequences from the 100 Scarlet Macaws sampled across the species’ range.

Phylogenetic reconstruction describes evolutionary relationships in terms of relative newness of common ancestry and was used on the sequence dataset, which revealed two major monophyletic groups (a term used to describe a group of organisms that are classified in the same species and share a most common recent ancestor), with near identical topologies recovered for both “ML” and “BI”, cf. above. The haplotypes within Ara macao cyanopterus formed a well-supported clade (a group of organisms believed to comprise all the evolutionary descendants of a common ancestor).

Five clusters of haplogroups (haplogroup is a group of similar haplotypes that share a common ancestor with certain other characteristics) were identified within Ara macao cyanopterus in the new study referred to as Haplo1, Haplo2, Haplo3, Haplo5 and Haplo6 - regarding the prevalence of the individual haplotypes, see the figure below). Haplo2 was found throughout in upper Central America, from Mexico to northeastern Costa Rica, whereas the remaining four haplogroups for Ara macao cyanopterus exhibited more restricted geographical distributions. Haplo1 and Haplo6 were both detected in Mexico and Guatemala. Haplo3 and Haplo5 demonstrated similar ranges along the Pacific slope of El Salvador, Honduras and Nicaragua, however, Haplo3 was also recovered on Isla Coiba, Panama. There is little divergence regarding relationships between Ara macao cyanopterus haplotypes, with the exception of Haplo2 appearing more diverged from the other four Ara macao cyanopterus haplogroups. Each Ara macao cyanopterus haplogroup clustered into a monophyletic group. Evolutionary relationships among the five haplogroups were poorly determined.

The population aggregation analysis showed no diagnostic characters correspond with the hypothesized subspecies border in central Nicaragua mentioned by David Wiedenfeld (1994). Instead, the geographical limit appears to occur further south in Costa Rica.

Ara macao macao was characterized by only two haplogroups (in the new study referred to as Haplo4 and Haplo7) with separate geographical ranges demarcated by the Andean Mountains. The Trans-Andean populations in Colombia and lower Central America belong to Haplo7, whereas Haplo4 is distributed throughout the huge Amazon Basin eastwards.

Here you see one of the figures from the new study showing the prevalence of the individual haplogroups mentioned above:

In compliance with the broadly sampled phylogenetic reconstructions the research team made, the sequencing and analysis of the full mitochondrial genomes of Ara macao cyanopterus and Ara macao macao showed clear separation of the two subspecies. Concerning molecular diversity average genetic distances between the two subspecies equaled 0,8 %.

The new study can therefore be said to "stand on the shoulders" of the work that other American scientists were doing back in 2013, when they in Texas initially succeeded in sequencing an overall genome for Ara macao.

Ara macao cyanopterus, an adult beautiful breeding pair in a nice big aviary. On one of the birds, you can see that the underside of the wings is red/reddish, which according to some aviculturists makes it a "true" Ara macao cyanopterus, although this is not substantiated by science.

Discussions

a) Evaluation of current taxonomy

The primary visual identifying characters for the Scarlet Macaw subspecies are listed as a generally larger size for Ara macao cyanopterus and the presence of a green band on the secondary wing coverts for Ara macao macao. However, previous examinations of morphometric data revealed weak differentiation of geographical variants (cf. David Wiedenfeld, 1994). Only wing chord-length demonstrated statistical significance when corrected for sex, significantly more for males. Likewise, the extent of green tips on secondary wing coverts, an ambiguous and subjective trait, exhibits a pattern of clinal variation (a gradual change in a character or feature across the distributional range of a species or population, usually correlated with an environmental or geographic transition); Ara macao cyanopterus is described as having little to no green colouration, whereas Ara macao macao exhibits small to substantial amounts of green plumage, with no empirical means to quantify “little” versus “small”. Relative to morphological data, a clearer picture emerges when we consider molecular genetic data. There is strong divergence between clades and sequence variation clearly differentiating the two Scarlet Macaw subspecies.

Ranging from Mexico to northern Costa Rica, Ara macao cyanopterus forms a well-supported monophyletic group consisting of five monophyletic haplogroups, with each pair differentiated by three to eight fixed nucleotide mutations. The new study shows these distinct haplogroups represent a single evolutionary entity.

The southern populations of Ara macao macao also form a monophyletic group, and they show less pronounced sequence divergence but greater geographical structure relative to Ara macao cyanopterus. Two fixed nucleotide mutations differentiate Cis-Andean from Trans-Andean populations, with an additional fixed nucleotide delineating Ara macao macao populations in southern Costa Rica and Panama. It is traditional to use the term Cis-Andean for species distributed East of the Andes (Amazonas) and the term Trans-Andean for those distributed West of the Andes (Central America).

Formal taxonomic descriptions include discussion of possible introgression between Ara macao cyanopterus and Ara macao macao, with the intergradation of colour variants occurring simultaneously with a steep decline in wing chord-length across southern Nicaragua and northern Costa Rica viewed as evidence of a hybrid zone (cf. David Wiedenfeld, 1994). However, the distribution of mtDNA haplotypes observed in this study demonstrates a general pattern of geographical isolation; no Ara macao cyanopterus haplotypes were detected on mainland Central America south of the Costa Rican cordilleras (a mountain range). The only instance of Ara macao cyanopterus haplotypes within the Ara macao macao distribution occurs on the large island, Isla Coiba, located near Panama.

This study found that Ara macao cyanopterus and Ara macao macao haplotypes are separated by the central cordilleras of Costa Rica, a volcanic mountain range varying in elevation from 500 to over 3,800 m and crosscutting the country, with near complete isolation of the Scarlet Macaw’s preferred lowland habitats along the Pacific and Caribbean slopes, suggesting that, if present, a present hybrid zone would probably be confined to a narrow geographical area.

The observed different patterns of molecular diversity and wide distribution of mitochondrial haplotypes support Ara macao cyanopterus and Ara macao macao as diagnosably distinct, reciprocally monophyletic and geographically isolated evolutionary units. To be “reciprocally monophyletic” is a term that typically applies to analyses of gene tree data from two sister species. If you consider two species, A and B, to say that they are reciprocally monophyletic means that all of the haplotypes sampled from species A are more closely related to each other than any haplotype from species B, and vice versa.

The research team therefore recommended recognizing Ara macao cyanopterus and Ara macao macao as two distinct subspecies, and - very important - representing two independent conservation units.

The nominate type of Scarlet Macaw (Ara macao macao), here a male from Bronx Zoo, US. On this specimen you clearly see the large areas of the green colour in the different wing coverts, and the greatly reduced number of yellow feathers in the same place, giving a somewhat more variegated impression of the bird. Photo from the Internet.

b) Patterns of diversification

Fluctuations in the distribution of habitats in response to changes in temperature and precipitation are commonly considered to be key factors governing the historical biogeography of lowland ecosystems across the Central and South America.

Regional differences in the intensity and duration of population fragmentation and associated demographic changes provide a theoretical framework to explain patterns of evolutionary divergence within Scarlet Macaws. In the case of Ara macao cyanopterus, the subspecies’ range encircles the Central American landmass, geographically constrained by an extensive system of central highlands and the coastal waters of the Atlantic and Pacific Oceans. The Scarlet Macaws’ preferred humid lowland habitats are heavily dependent on the availability of fresh water, and thus shifts in distributions would closely follow this critical resource. The genetic signatures recovered among mtDNA haplotypes may reflect the fragmentation of ancestral Ara macao cyanopterus into allopatric refugia (non-overlapping distribution areas during periods of unfavourable conditions). The presence of several distinct Ara macao cyanopterus haplogroups appears to increase levels of overall sequence variation, as diversity indices decline for the majority of haplogroups when treated as separate units.

A completely different pattern of genetic variation emerges upon examination of Scarlet Macaw populations across lower Central and South America. Ara macao macao is represented by only two haplogroups, differentiated by two fixed nucleotide bases and geographically separated by the Andean Mountains.

c) Conservation implications and threats

Common throughout its global distribution through the ages, populations of Scarlet Macaws have experienced widespread demographic declines and local extinctions due to capture for the pet trade and habitat destruction. Furthermore, anthropogenic pressures have been most severe in Central America, where high human population densities and associated resource demands put tremendous strain on the region’s ecosystems. This has resulted in a 22 % reduction in primary forest within a 20-year period from 1990 to 2010 (FAO 2010).

The confirmation of genetic diversity reveals a critical gap between conservation needs and conservation status for these charismatic parrots. At present, Scarlet Macaws are considered a species of “Least Concern”, given global demographic trends, population size and extent of available habitat are above designated thresholds for threatened status (IUCN 2015). Splitting Scarlet Macaws into two distinct conservation units, however, immediately transforms the conservation status of this group. Approximately 83 % of preferred lowland habitats are located within the Amazon Basin, along with the majority of the estimated census population of 50,000 - 499,999 individuals for Ara macao with an estimated range of occurence on 10,200,000 km2 (BirdLife International 2024). Deforestation rates are declining throughout South America, dropping from 0.49 to 0.41 % in the past decade (FAO 2010), with human population growth rates falling in concert from 1.17 % to 1.07 % (CEPAL 2013). Therefore, robust populations of Ara macao macao ranging across the Amazonian lowlands may indeed qualify for “Least Concern” status.

Opposite, the situation faced by Scarlet Macaws in Central America is far more precarious. Annual human population growth rates are currently 1.59 % and human densities are 4.2-fold greater relative to South America, putting tremendous strain on the region’s natural resources. Forest area in Central America declined by an average of 1.19 % annually between 2000 and 2010, the highest rate reported by the United Nations (FAO 2010). The loss of important foraging and nesting habitats, coupled with intense nest poaching for the pet trade, have decimated Ara macao cyanopterus with fewer than 4.000 wild Ara macao cyanopterus remaining in isolated forest fragments throughout upper Central America. Recovery of five unique mitochondrial haplogroups within the Ara macao cyanopterus lineage highlights the evolutionary significance of these populations, further advocating that Ara macao cyanopterus should be uplisted to “Vulnerable” status.

d) Rigorous delineation of conservation targets is needed

The new study also pointed out that current conservation designations may need to be re-evaluated. The use of the term “subspecies” in taxonomy and conservation biology is considered somewhat controversial given the arbitrary assessment criteria’s and poor connections to evolutionary history. Therefore, rigorous delineation of conservation targets within Scarlet Macaws is needed to create a solid foundation for conservation assessment, management strategies, ease of daily handling, etc. The new study has helped to create such clarity, and a clear definition of a subspecies provides a unique conservation target, which hopefully may help to save it in its natural habitats in the long run.

As already stated, it is estimated that fewer than 4,000 Ara macao cyanopterus remain in wildlife in Central America, scattered across areas in smaller isolated forest fragments which makes it very vulnerable. In comparison, BirdLife International estimates that there are 4,300 Hyacinth Macaws (Anodorhynchus hyacinthinus) left in the wild with a much larger range of 2,850,000 km2, and it is categorized as “Vulnerable”.

It is my assessment that if Ara macao cyanopterus in the future can become an independent wild conservation subject, the chances for protecting these wonderful birds in the wild will be much better. However, BirdLife International still only operates with the Scarlet Macaw (Ara macao) on species-level. As the Scarlet Macaw (Ara macao) in general is widely distributed and thought to be relatively tolerant of degraded habitat, the species is considered of “Least concern” by the IUCN (2016) and BirdLife International though it also is listed under Appendix I of CITES.

In this area, the United States is significantly further ahead; in 2019 Scarlet Macaws (Ara macao) received protection under the United States Endangered Species Act (ESA). The northern subspecies of the Scarlet Macaw (Ara macao cyanopterus) has thus been listed as endangered and a distinct population segment (DPS) of the southern subspecies (Ara macao macao) as threatened. The southern subspecies (and strangely enough subspecies crosses as well) of the Scarlet Macaw are also added to an existing special rule for parrots under section 4(d) of the ESA. This continues to provide needed protections while allowing for interstate commerce and the import and export of certain captive-bred birds provided the requirements of the Wild Bird Conservation Act and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) are met. So, the Scarlet Macaw is now protected by both this important U.S. conservation law and by the international conservation agreement.

This is also a Scarlet Macaw with a nice yellow wing band, but notice the relatively few green feathers. According to the scientific description of Ara macao cyanopterus, a certain amount of green is acceptable. It is therefore important that you also use the well-known morphological visual features that characterize this subspecies to be more certain that it is an Ara macao cyanopterus and not a cross-bred bird.

Some conclusions on the study

In 1994 the scientist David Wiedenfeld proved the existence of two different subspecies of Ara macao through studies of purely morphological features and colour variation in the plumage. The new scientific study (2019) from Columbia University etc. has through genetic analysis confirmed the existence of these two - and only two – subspecies, and this new study has even revealed strong phylogeographical divergences within the Scarlet Macaw (Ara macao).

Together with phylogenetic reconstruction and population aggregation analysis the new study has thus confirmed the existence of two distinct phylogeographical groups, with a high degree of intraspecific genetic structure and surprisingly no evidence of a putative hybrid zone as David Wiedenfeld’s study from 1994 had otherwise assumed. Instead, it is rather considered to be an actual physical segregation between the two subspecies that occur further south in Costa Rica.

Up until now the two subspecies have been weakly differentiated, but this has changed with the new study. Through the new study the whole mitochondrial genome sequence has been uncovered and has confirmed a substantial divergence between the Ara macao macao - and the Ara macao cyanopterus-lineages.

The huge geographical range of the Scarlet Macaw’s preferred habitats has thus undergone significant changes across evolutionary time, caused by major geological events and climatic fluctuations through the ages. The results show a separation of Ara macao into two distinct evolutionary entities and highlight a dissimilar distribution of intraspecific diversity, especially in relation to Ara macao cyanopterus caused by phylogeographically conditioned fragmented presence in its much smaller habitat areas. The Ara macao cyanopterus thus lives in several isolated populations. Although each population now may be large enough to avoid genetic inbreeding problems, because the populations are small and isolated, their long-term survival unfortunately were already assessed unlikely by David Wiedenfeld (1994).

Ara macao macao was characterized by only two haplogroups with separate huge geographical ranges divided by the Andean Mountains. On the other hand, Ara macao cyanopterus consists of 5 different haplotypes according to the new study, which means a significant differentiation in its genotype, which - in my humble opinion - most likely will be visible through higher differentiation in its phenotype, typically shown as differences in the colouration of the plumage.

With these two scientific studies of the Scarlet Macaw (Ara macao), serious aviculturists now have much better possibilities to distinguish the two subspecies from each other and thus breed with each subspecies separately. However, the scientific work so far is not quite enough to in practice always be able to distinguish the two subspecies (without genetic tests). Over time, knowledge of other visual characteristics per subspecies has been built up among particularly interested aviculturists. Below is a brief overview of some of these non-scientific characteristics, or rather perceptions, although not all of them are valid in my opinion.

Ara macao cyanopterus, a few months old birds. In Denmark, the wind blows very often and much, so much so that the birds - when sitting in outdoor aviaries - almost push themselves down along the perch or branch on which they sit with their beaks pointing towards the wind, as otherwise they will not be able to control their very long tails, which precisely characterizes this subspecies.

Views on Ara macao cyanopterus among some aviculturists

Over recent years some aviculturists, that have shown interest for - or even are keeping/breeding - Ara macao cyanopterus, have either heard about or have developed many perceptions of how this subspecies should look like, their size, tail length and width, etc.

Some of these perceptions are listed in the following and they affect both morphological (physical) features and colour differences in the plumage, that should characterize this subspecies. Be aware that these perceptions are not supported by scientific evidence, but typically solely rest on “reports and rumors” among aviculturists, etc. Nevertheless, some of them might provide a more complete picture of how a “true”Ara macao cyanopterus should look like, when one combines it with the scientific phenotypic features mentioned above, so it hopefully better can be visually distinguished from the nominate subspecies (Ara macao macao).

a) Morphological (physical) features:

• The perception that the tail feathers on the Ara macao cyanopterus should be of a certain length and width are not supported by scientific evidence in the two studies mentioned in this article, but of course this subspecies according to David Wiedenfeld should be more robust (a single very big captive bird, for example, has weighed up to nearly 1,600 grams) and longer than Ara macao macao. The tail appears disproportionately long and among aviculturists there seems to be a common opinion that the tail length on Ara macao cyanopterus most often should be 60 - 70 cm or more. The width of the longest tail feathers on males can measure up to 5 - 6 cm, on some occasions even wider, in certain areas of the feather.
• Another significant difference seems to be that the whole tail of the Ara macao cyanopterus apparently appears to be of a certain width throughout its length, whereas the tail of the nominate subspecies, the Ara macao macao, appears to be more wedge-shaped as e.g., seen among a number of South American parakeets for example the Psittacara-genus.
• Even the physical structure of the tail of an Ara macao cyanopterus is also said to be very different compared to the tail on an Ara macao macao. It is said that the middle part of the tail on the Ara macao cyanopterus consist of two long center tail feathers, and the tip may, by virtue of the length of the tail, have a tendency to bend downwards. In contrast, the middle part of the tail on the Ara macao macao should consist of a single centered tail feather.
• Some aviculturists believe, that the Ara macao cyanopterus coming from Nicaragua - in general or at least in some cases - seems larger than other specimens coming from other parts of the range of Ara macao cyanopterus. Several samples of Scarlet Macaws from Nicaragua were used in both scientific studies (1994 and 2019) and no notes have been made to substantiate this perception by scientific evidence. Among a large population of birds there will always be a variation in size, colouration, etc., and some individuals will seem bigger and more colourful than others. This is far from always due to genetic conditions, but instead this may be due to the fact that the birds have had different living conditions, for example differences in the nutritional value of the feeding during the upbringing, the extent and nutritional value of the feeding in daily life, the birds you compare have different ages, sex, different access to nesting facilities, etc. However, local populations of large types of certain other Macaw species are not unknown: For many years it has been common knowledge among aviculturists, that specimens of both the Blue and Yellow Macaw/Blue and Gold Macaw (Ara ararauna) and the Red and Green Macaw/Green-winged Macaw (Ara chloropterus) that come from Bolivia appear to be significantly larger than similar birds that come from other parts of the large range of these two species. On the other hand, the Bolivian specimens of these two species are not significantly different in the colouration of the plumage apart from minor exceptions. Both of these species are monotypic species, as science does not recognize any subspecies of either Ara ararauna or Ara chloropterus. In these cases, it is a matter of species variance. Finally, a few aviculturists claim that certain Scarlet Macaws that come from Bolivia in some physical body areas also show larger size.

A huge and adult Ara macao cyanopterus, an impressive, robust male bird with a very long and wide tail that characterizes an Ara macao cyanopterus.

b) Colour differences in the plumage:

• As I write - to my knowledge - there is no scientific evidence, that the underside of the wings of Ara macao cyanopterus only should be red/reddish, while the underside of the wings of Ara macao macao should be yellow/yellowish. The study that David Wiedenfeld completed in 1994 does not shed light on such a difference. When evaluating the significance of this alleged characteristic you should - according to my own experience - take into account what age the bird is. Next to this, it is of utmost importance that two (or more) different birds are compared under identical lighting conditions. Depending on whether you observe the underside of wings in day light (including flash light) or in clouded weather reddish coloured underside of the wings can seem yellowish in bright, sunny weather and yet perceived as red/reddish in clouded weather.
• When you observe - or rather examine - a Scarlet Macaw the age of the bird is also important to know, because the colours of this bird's plumage to a certain extent may change over time, especially when it comes to birds in human care as their life span often are much longer than birds living in the wild. Not least in the birds' first years of life, there may be visible changes in the colouration of the plumage. Conversely, large colour differences can also occur among very old individuals (from around 20 years old), where the yellow feather areas in the wings of some specimens may vanish and instead - more or less - replaced by red feathers.

The large colour differences that often can be observed in the plumage of Scarlet Macaws have over the years got aviculturists (not least in the US) to group these birds into 3 or even 4 different types depending on their place of origin. Regardless of such groupings, we now know for sure that science has proven that two - and only two - genetically very different subspecies of Scarlet Macaws exist. Nevertheless, in nature we can also observe differences in the looks of Scarlet Macaws sitting together in a flock in the same place, but these must be considered as natural varieties as we know it from many other kinds of animals.

However, it should not stop me from briefly mentioning one of these non-scientific groupings based on the birds' different colouration (phenotype) based on place of origin in nature. Below is an American example of a non-scientific grouping of Scarlet Macaws into three different types:

It's unfortunately not the clearest photo one could have wished for however, on these few months old young birds which are bathing in the rain, you can see that the underside of the wings is red/reddish, as some aviculturists believe they must be in order to be a "true" Ara macao cyanopterus, but there is currently no scientific evidence for this view.

• The Mexican Scarlet Macaw-type:

They are quite colourful and are characterized by a narrow yellow band of feathers on the wing nestled between the red feathers on the shoulder and the blue flight feathers, generally only two rows wide (the edges of the yellow wing coverts being coloured with shades of blue to green). These are not huge birds overall; a collection of Mexican Scarlet Macaws has shown an average weight of 908 grams. Their range has been considerably reduced in Mexico due to deforestation for agriculture, now limited to where there still are jungles. At one point, they ranged all the way up the east coast of Mexico to just before the northern deserts. Most of the Mexican type still living are in small local forested areas of southern Mexico.

• The Central American Scarlet Macaw-type:

The Central American Scarlets Macaws come from lower Central America (Nicaragua, Costa Rica, parts of Honduras and Panama, and occasionally as far north as Guatemala) and are considered the largest and most spectacular Scarlet Macaws to be seen. Some people have been bragging of tail feathers up to 90 cm. Central American Scarlets range in weight from 1,190 to 1,560 grams for males and 1,048 to 1,162 grams for females. These large birds have the widest band of yellow feathers that when combined with the long tail feathers identify them as Central American Scarlets. The yellow wing band is three to four feathers wide and edged by greenish-blue tips, but only a slight amount of the tip of the yellow feather is covered by this greenish-blue colour.

• The South American Scarlet Macaw-type:

South American Scarlet Macaws are generally not as large as Central American Scarlet Macaws and have a narrower band of yellow feathers, very similar to the Mexican Scarlet Macaw-type, that is bordered in green and - in some specimens - also blue. The weight is average 1,219 grams for males and 1,162 grams for females. Their range in nature have been reduced significantly, until the last vestiges are in the Amazon Basin, at elevations under 400 m. The marking that differentiates this type from the other two is a large turquoise-green area, commonly the size of a tablespoon, found on the nape of the neck.

To determine whether a certain Scarlet Macaw belongs to one or the other of the two subspecies can be difficult, and the many cross-bred birds among aviculturists make it even more difficult. A Scarlet Macaw with completely yellow median and secondary wing coverts is not always an Ara macao cyanopterus. You must - as described in this article - also look into other criteria’s as well, mainly morphological traits such as the size of the bird, the size of the beak and especially the length of the wing chords and of course the length and width of the tail, and not to forget - the weight. Therefore, strive to keep the two subspecies separated from each other when breeding Scarlet Macaws.

A general description of the Scarlet Macaw can be found in several serious non-fiction books such as the magnificent, “Parrots of the World” (1st edition 1973, or later editions), by the excellent Australian ornithologist, Joseph M. Forshaw, to which reference is made.

Jørgen Petersen

Written / Updated: 31.01.2021 / 03.04.2024

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