Ultraviolet-sensitive vision in long-lived birds

Long-term exposure to ultraviolet (UV) light generates substantial damage, and in mammals, visual sensitivity to UV is restricted to short-lived diurnal rodents and certain marsupials. In humans, the cornea and lens absorb all UV-A and most of the terrestrial UV-B radiation, preventing the reactive and damaging shorter wavelengths from reaching the retina. This is not the case in certain species of long-lived diurnal birds, which possess UV-sensitive (UVS) visual pigments, maximally sensitive below 400 nm. The Order Psittaciformes contains some of the longest lived bird species, and the two species examined so far have been shown to possess UVS pigments. The objective of this study was to investigate the prevalence of UVS pigments across long-lived parrots, macaws and cockatoos, and therefore assess whether they need to cope with the accumulated effects of exposure to UV-A and UV-B over a long period of time. Sequences from the SWS1 opsin gene revealed that all 14 species investigated possess a key substitution that has been shown to determine a UVS pigment. Furthermore, in vitro regeneration data, and lens transparency, corroborate the molecular findings of UV sensitivity. Our findings thus support the claim that the Psittaciformes are the only avian Order in which UVS pigments are ubiquitous, and indicate that these long-lived birds have UV sensitivity, despite the risks of photodamage.     

Laterality enhances cognition in Australian parrots

Cerebral lateralization refers to the division of information processing in either hemisphere of the brain and is a ubiquitous trait among vertebrates and invertebrates. Given its widespread occurrence, it is likely that cerebral lateralization confers a fitness advantage. It has been hypothesized that this advantage takes the form of enhanced cognitive function, potentially via a dual processing mechanism whereby each hemisphere can be used to process specific types of information without contralateral interference. Here, we examined the influence of lateralization on problem solving by Australian parrots. The first task, a pebble-seed discrimination test, was designed for small parrot species that feed predominately on small seeds, which do not require any significant manipulation with the foot prior to ingestion. The second task, a string-pull problem, was designed for larger bodied species that regularly use their feet to manipulate food objects. In both cases, strongly lateralized individuals (those showing significant foot and eye biases) outperformed less strongly lateralized individuals, and this relationship was substantially stronger in the more demanding task. These results suggest that cerebral lateralization is a ubiquitous trait among Australian parrots and conveys a significant foraging advantage. Our results provide strong support for the enhanced cognitive function hypothesis.     

Conservation status of parrot populations in an Atlantic rainforest area of southeastern Brazil

A census of four species of syntopic parrots was carried out using distance sampling methods on São Sebastião island, SE Brazil. Most of the 33593 ha island is covered by mature and secondary Atlantic rainforest. Almost 80% of these forests are within the Ilhabela Park. Although the species counted have marked differences in size and weight, density (individuals/km²) and estimated population size in 23500 ha of well-preserved forests were similar: Amazona farinosa (13.82±5.94; 3247±1395), Pionus maximiliani (15.79±7.04; 3712±1654), Brotogeris tirica (15.05±4.87; 3537±1143) and Pyrrhura frontalis (13.06±5.53; 3068±1298). Encounter rates of Forpus crassirostris and Pionopsitta pileata were very low, which suggests that there is only a small population of these species on the island. The São Sebastião forests still support healthy populations of parrots. Although woodpecker population estimates on the island are large enough to provide nesting sites for parrots, competition for holes with other secondary cavity nesters such as toucans, flycatchers and tytiras, and the selective cutting of dead trees for canoe construction, which is a common practice on the island, may limit hole availability for parrots.     

Morphogenesis of parrot jaw muscles: understanding the development of an evolutionary novelty

Parrots have developed novel head structures in their evolutionary history. The appearance of two new muscles for strong jaw adduction is especially fascinating in developmental and evolutionary contexts. However, jaw muscle development of parrots has not been described, despite its uniqueness. This report first presents the normal developmental stages of the cockatiel (Nymphicus hollandicus), comparable to that of the chick. Next, the peculiar skeletal myogenesis in the first visceral arch of parrots is described, mainly focusing on the development of two new jaw muscles. One of the parrot-specific muscles, M. ethmomandibularis, was initially detected at Nymphicus Stage 28 (N28) as the rostral budding of M. pterygoideus. After N32, the muscle significantly elongates rostrodorsally toward the interorbital septum, following a course lateral to the palatine bone. Another parrot-specific muscle, M. pseudomasseter, was first recognized at N36. The muscle branches off from the posteromedial M. adductor mandibulae externus and grows in a dorsolateral direction, almost covering the lateral surface of the jugal bar. The upper tip of the muscle is accompanied by condensed mesenchyme, which seems to be derived from cephalic neural crest cells.     

Parrot conservation in a small island-nation: Case of the Commonwealth of Dominica

The Commonwealth of Dominica, hereafter referred to as Dominica, is one of only two islands in the English-speaking Caribbean with two species of extant, endemic Amazona parrots, namely the Imperial or Sisserou Parrot (Amazona imperialistand the Red-necked or Jaco Parrot (A. arausiaca).These birds are of national as well as international significance, as their populations have been on the decline for several years. During the last 15 years the local authorities, with the support and cooperation of various regional and international agencies, have mounted a campaign to save both species from extinction. An islandwide public awareness campaign has been attempted, with encouraging results. An increase in the species population as well as an increased level of private and public support for parrot conservation, are among the positive results to date. In spite of these accomplishments, however, the parrots are not out of danger and therefore continued vigilance is necessary. Additional measures are proposed to ensure the continued existence and complete recovery of the Dominican Amazons.     

Historical biogeography and diversification within the Neotropical parrot genus Pionopsitta (Aves: Psittacidae)

Aim We investigate spatial and temporal patterns of diversification within the Neotropical avifauna using the phylogenetic history of parrots traditionally belonging to the genus Pionopsitta Bonaparte 1854. This genus has long been of interest for those studying Neotropical biogeography and diversity, as it encompasses species that occur in most Neotropical forest areas of endemism. Location The Neotropical lowland forests in South and Central America. Methods Phylogenetic relationships were investigated for all species of the genus Pionopsitta and five other short‐tailed parrot genera using complete sequences of the mitochondrial genes cyt b and ND2 as well as 26 plumage characters. The resulting phylogeny was used to test the monophyly of the genus, investigate species limits, and as a framework for reconstructing their historical biogeography and patterns of diversification. Results We found that the genus Pionopsitta, as previously defined, is not monophyletic and thus the Chocó, Central American and Amazonian species will now have to be placed in the genus Gypopsitta. The molecular and morphological phylogenies are largely congruent, but disagree on the position of one of the Amazon basin taxa. Using molecular sequence data, we estimate that species within Gypopsitta diversified between 8.7 and 0.6 Ma, with the main divergences occurring between 3.3 and 6.4 Ma. These temporal results are compared to other taxa showing similar vicariance patterns. Main conclusions The results suggest that diversification in Gypopsitta was influenced mainly by geotectonic events, marine transgressions and river dynamics, whereas Quaternary glacial cycles of forest change seem to have played a minor role in the origination of the currently recognized species.     

The influence of spatial resolution on macroecological patterns of range size variation: a case study using parrots (Aves: Psittaciformes) of the world

Aim To assess the extent to which the resolution at which geographical range sizes are measured influences macroecological patterns in this variable. Location Global. Methods Data on the geographical ranges of parrot species were digitized, and a Geographic Information System used to produce nine range size estimates for each species using different degrees of spatial resolution. The inter‐correlation of these estimates was then compared, together with their patterns of covariation with population size, body mass and migratory behaviour (across species and controlling for phylogeny), their pattern of phylogenetic correlation, and the frequency distributions of the different measures. Results Strong correlations exist among all nine range size measures across species, albeit that measures of similar spatial resolution are more strongly correlated. All measures show similar patterns of covariation with population size, body mass and migratory behaviour, and similar patterns of phylogenetic correlation. The skewness of frequency distributions increases towards zero as the resolution of the range size measure declines. Main conclusions The results of macroecological analyses are little affected by the resolution with which geographical range sizes are calculated, at least for the parrots of the world. Previously published studies based on crude measures of range size would be unlikely to have produced markedly different conclusions had they used more refined range size metrics.     

Founder populations and the current status of exotic parrots in South Africa

Parrots (families Psittacidae and Cacatuidae) are one of the most threatened taxa of birds, with a combination of threats to wild populations, including capture for the cage bird market, habitat modification and destruction, persecution, disease, and threats from introduced species. As a result of the group's popularity as a cage bird, and the transport of vast numbers of individuals across the globe (both legally and illegally), the establishment of populations beyond their natural ranges has likely been enhanced. This review reports on c. 30 parrot species that have been observed outside of their natural ranges in South Africa, most likely derived, and supplemented, from both intentional and unintentional releases. Of these, the Rose-ringed Parakeet Psittacula krameri and at least one Agapornis species have become established as breeding wild populations. Like other invasive species they may pose threats to local biodiversity; however, all are strongly associated with major urban centres where significant changes to natural biota have already occurred.