Psittacus
Psittacus is a genus of parrots in the family Psittacidae, endemic to the equatorial forests of West and Central Africa, consisting of two recognized species: the grey parrot (Psittacus erithacus) and the Timneh parrot (Psittacus timneh).[1] These medium-sized birds are characterized by predominantly grey plumage, strong curved beaks adapted for cracking nuts and seeds, and zygodactyl feet suited for arboreal life, with the P. erithacus featuring a bright red tail and the P. timneh a maroon one.[2] Renowned for their cognitive prowess, individuals of this genus have demonstrated abilities in vocal mimicry, concept formation, and problem-solving in controlled studies, such as the work with the specimen Alex, which exhibited referential use of labels and numerical competence comparable to young primates.[3][4] Both species face severe population declines, classified as Endangered by the IUCN due primarily to unsustainable capture for the international pet trade and habitat degradation, leading to their listing under CITES Appendix I prohibiting commercial trade.[5][6]Taxonomy and Classification
Species and Subspecies
The genus Psittacus comprises two extant species: the grey parrot (Psittacus erithacus) and the Timneh parrot (Psittacus timneh).[7][8] P. timneh, previously classified as a subspecies (P. e. timneh), was elevated to full species status in 2012 by BirdLife International following multilocus genetic analyses that revealed substantial divergence from P. erithacus, including fixed differences in mitochondrial DNA control region sequences and distinct vocal repertoires indicative of reproductive isolation.[8][9] This split is supported by phylogenetic evidence showing reciprocal monophyly between the two taxa, with P. timneh exhibiting lower genetic diversity and closer affinity to island populations than previously assumed.[10] Within P. erithacus, two subspecies are recognized in certain taxonomic frameworks, including the nominate P. e. erithacus (Congo grey parrot), distributed across mainland equatorial Africa from southeastern Côte d'Ivoire eastward, and P. e. princeps from Príncipe Island in the Gulf of Guinea.[11][12] Genetic studies using cytochrome b and control region markers demonstrate moderate differentiation between P. e. princeps and mainland P. e. erithacus (F_ST ≈ 0.15–0.20), attributable to geographic isolation over approximately 1–2 million years, though gene flow estimates remain low but non-zero.[13][14] Delineation relies on empirical criteria such as allopatric distributions, subtle plumage variations (e.g., tail hue), and morphometric differences, corroborated by eBird's 2023 taxonomy which maintains princeps as a distinct entity pending further genomic data.[15][10] The validity of princeps has been questioned in some classifications due to overlapping genetic signals with P. timneh, but phylogenetic clustering supports its retention as a subspecies of P. erithacus based on available evidence from limited sampling (n=20 island individuals).[13][10]Phylogenetic Relationships
Psittacus is classified within the family Psittacidae, specifically the subfamily Psittacinae, which comprises a low-diversity radiation endemic to Africa and also includes the genus Poicephalus.[16] This subfamily diverged from the Neotropical Arinae clade in the early Oligocene, approximately 30 million years ago, marking an early split within Psittacidae that underscores Psittacus's basal position relative to other African parrot lineages beyond Psittacinae.[16] [17] Multilocus molecular analyses, including mitochondrial and nuclear markers, consistently recover Psittacinae as sister to Arinae, rejecting earlier morphology-based groupings that conflated African and Indo-Malayan parrots.[17] Within Psittacus, P. erithacus and P. timneh form a sister species pair, with genomic phylogenies based on over 1 million sites confirming their reciprocal monophyly and divergence approximately 1.9 million years ago in the early Pleistocene.[16] [13] Mitochondrial DNA sequences, such as cytochrome b, reveal strong genetic differentiation, with estimates of divergence up to 2.4 million years ago, supporting their distinction from neighboring genera like Poicephalus.[10] This separation is further evidenced by the Príncipe Island population's closer affinity to timneh than to erithacus, highlighting vicariant evolution across West African barriers.[13] Historically, P. timneh was treated as a subspecies of P. erithacus based on morphological similarities, but molecular phylogenies from the mid-2000s onward resolved this by demonstrating sufficient genetic and vocal divergence for full species status, formalized around 2012.[13] [9] These findings, integrated into 2024 phylogenomic syntheses, prioritize nuclear and mitochondrial data over prior assumptions, affirming Psittacus as a distinct lineage with no close relatives outside its recognized species.[16]Physical Characteristics
Morphology and Plumage
Psittacus species are medium-sized parrots characterized by predominantly grey plumage, a distinctive tail color, white bare skin surrounding the eyes forming a periophthalmic ring, and a robust, hooked black bill in P. erithacus.[18] The feathers of P. erithacus vary in shades of light grey, appearing slightly darker on the wings and back, with scarlet red tail feathers providing contrast.[5] In contrast, P. timneh exhibits darker grey overall plumage, maroon rather than scarlet tail feathers, and a pinkish-grey upper mandible contrasting with the darker lower mandible.[19] These parrots possess zygodactyl feet, a typical avian adaptation in Psittaciformes with digits II and III directed forward and IV backward, enabling precise perching and manipulation.[20] The bill is strong and curved, adapted structurally for exerting force on hard objects, as evidenced by detailed musculature studies.[21] Juvenile Psittacus individuals resemble adults in plumage but differ in eye color, with dark grey to black irises maturing to pale yellow in adults around 2-3 years of age; bill coloration in juveniles tends toward a lighter, horn-like tone before darkening.[22] Body length averages 33 cm for P. erithacus and 28-30 cm for P. timneh, with corresponding weights of approximately 400-500 g and 275-375 g, respectively, based on field observations and avicultural records.[18] [22] Plumage maintenance involves periodic molting, with no significant sexual dichromatism observed in either species.[23]