As we have seen, the dispersal of songbirds from their proto-Papuan birthplace reached all continents except Antarctica: a radiation that came to dominate the Earth’s avifauna. In the process, populations became fragmented and reproductively isolated, so spawning new species, lineages and families. Some groups underwent explosive multidirectional long-distance dispersals while others used islands as stepping stones for a more gradual expansion. Along the way, mountainous areas provided hotspots of diversity, especially those of central and southwestern China, a reflection of their complex topography and the resultant panoply of ecological niches.1
After crossing the Beringian land bridge into North America during the Miocene, the songbird clade rapidly diverged and radiated across the New World. The largest of these branches was that of the nine-primaried oscines (superfamily Emberizoidea): a lineage that contains nearly 8 per cent of all extant bird species. Their name refers to the presence of just nine primary feathers on each wing compared to the ancestral state of ten (in reality, they all have a tenth primary, but it is markedly reduced and largely hidden).2 The Emberizoidea include the New World blackbirds and orioles (Icteridae), cardinals (Cardinalidae), Hawaiian honeycreepers (still formally classified within the Fringillidae), New World sparrows (Passerellidae), tanagers (Thraupidae) and New World warblers (Parulidae), as well as a ragbag of less notable groups. One offshoot even backtracked across Beringia and recolonised the Old World around 12 million years ago to give rise to the buntings (Emberizidae).3 Even though other groups have undertaken reverse dispersals (see The Thrush’s Story), the buntings are the only passerines to have done so through Beringia. This unique dispersal probably accounts for the relative paucity of buntings in western Europe compared to Asia and the Americas.
At first, the Panama seaway restricted the songbirds’ southerly dispersal, but as the gap between the two American continents started to close around 13 million years ago, not just birds but many species of land and freshwater fauna began to cross from one side to the other. Although slow at first, the bi-directional flow speeded up, especially after the land bridge was completed around 3 million years ago. The ‘great American biotic interchange’ was the end of the ‘splendid isolation’ for the South American suboscines.4 From now on, they faced competition from their newly arrived cousins from the north.
Despite being able to fly, the forest understorey-specialising suboscines were slow to disperse northwards and only did so after the Panamanian isthmus had fully formed. Furthermore, except for the tyrant flycatchers, very few suboscines made it further north than the border between Mexico and the United States. In contrast, the songbird generalists reached South America millions of years before the closure of the seaway, with taxa from several families, including finches, larks, pipits, sparrows and wrens, eventually reaching Tierra del Fuego. Remarkably, a single species, the South Georgia Pipit, even reached as far south as the Antarctic regions – the only passerine to do so.
Overall, the north–south interchange transformed the tropical avifauna of the New World and reshaped the patterns of biodiversity across many taxonomic families. But how is it that the invading songbirds were able to out-compete the suboscines and replace them in the forest canopy and open habitats?
It is commonly assumed that endemic lineages are better adapted to their home environment than new arrivals, but this is not always the case, as evidenced by many studies of island faunas. One explanation, according to the ornithologist and ecologist Robert Ricklefs, relates to their morphology: songbirds have longer legs and toes than suboscines and can engage in more active movement through vegetation. Their more generalised behaviour and diets, including greater intratropical migratory tendencies, would have been advantageous during the deteriorating climates of the Miocene and Pliocene.5 Most suboscines feed only on large insects, often using sit-and-search tactics, while oscines make greater use of fruit, consistent with their dominance in forest canopies. It is only the wrens that resemble the suboscines, and this is the one group of songbirds that has been successful in the forest interiors of South America. Furthermore, the ability of oscines to respond more rapidly to resource fluctuations, as well as their shorter incubation times and overall faster pace of life, would have helped. Indeed, it has been argued that their higher metabolic rate acted as an ‘intrinsically superior trait’ and that this was the primary factor that underpinned their global dominance.6
The first songbirds to cross the Panama seaway gave rise to the tanagers, a family that accounts for around 4 per cent of all avian species and nearly 12 per cent of all Neotropical birds. After reaching northern South America, the ancestral population underwent rapid diversification, leading to a bewildering array of plumage colours, morphologies, behaviours and foraging strategies that include thick-billed seed-eaters, thin-billed nectar-feeders, aerial insect-foragers, foliage-gleaners, bark-probers and frugivores. Before the advent of molecular genetics, such extreme diversity resulted in taxonomic confusion, with convergent evolution concealing many relationships. It now turns out that some taxa that look like tanagers, such as the Hepatic Tanager and Scarlet Tanager, as well as the ant tanagers, are not tanagers at all, but cardinals. In contrast, the Coal-crested Finch and Plushcap, as well as the honeycreepers, seedeaters, conebills, saltators, Darwin’s finches and flowerpiercers, have all been reclassified recently as tanagers, despite not looking at all like them.7
The Plushcap is named for its unusual dense, golden-yellow forecrown of stiff feathers that are less susceptible to wear and more resistant to moisture than typical feathers. Such a morphological feature may be an adaptation for its specialised feeding mode, in which it probes dense whorls of bamboo for small insects and plant material.8 In contrast, the Coal-crested Finch is a fire-following specialist of Brazil’s grasslands, with no close living relatives. Not only are its plumage colours and pattern unlike any other family member, but both male and female possess a crest, a relatively rare feature among the tanagers.
Most speciation events within the Thraupidae coincided with the accelerated uplift of the Andes which occurred between the Miocene and early Pliocene (12 to 4.5 million years ago), when habitat change, climate cycles and tectonic activity created many new opportunities for isolation. More recently, repeated invasions of Central America, encouraged by the formation of the Panamanian isthmus, led to further diversification. Sea-level changes may also have been a factor. For example, the Lesser Antillean Saltator, a taxon endemic to the Caribbean islands, and the Green-winged Saltator, a species restricted to the Brazilian Shield, diverged from a common ancestor half a million years ago. The Lesser Antilles were never connected to South America, except for the island of Trinidad, and it is likely that the lowered sea levels during the Pleistocene facilitated access from a mainland ancestor. Furthermore, the lack of genetic differences between four island populations of saltator suggests that this was a single, rapid colonisation event.9
The seedeaters are now classified as tanagers, despite being relatively small birds with stubby, conical beaks adapted for feeding on seeds and grain (most tanagers are omnivores with a diet consisting mainly of fruit, nectar and insects). Eleven members of the Sporophila genus, colloquially known as ‘southern capuchinos’ due to the head colouration of the males, have provided fascinating insights into the mechanisms of speciation. These finch-like birds inhabit the grasslands of northeastern Argentina, Uruguay, Bolivia and Southern Brazil. Leonardo Campagna, an Argentinian evolutionary biologist working at Cornell University, became intrigued by this sympatric group of birds after noticing that despite their marked variations in plumage, they could not be separated by standard DNA analysis, despite using thousands of genome-wide polymorphisms. However, species-specific genetic variations must exist, given their marked phenotypic differences. This observation led the researchers to speculate that substitutions in one or more critical genes must have occurred so fast that the random, or stochastic, changes in neutral markers that they had used for lineage assignment had not kept pace.10 But which genes could be involved, and how and why did they mutate so quickly?
A universal characteristic of seedeaters is their sexual dimorphism, or dichromatism, with males exhibiting a variety of colourful plumages that they use to attract females and to defend territories. While all 11 capuchino seedeaters have a cinnamon-based plumage, the presence or absence of white, black and grey patches characterises the different species. The females of these 11 species, in contrast, are indistinguishable morphologically, and cannot even be identified when in the hand. Of course, other birds can recognise their own kind, probably by detecting specific ultraviolet colour plumage patterns.11 The unusual features of capuchinos – marked genetic homogeneity, distinct phenotypes and overlapping geographical distributions – led Campagna to hypothesise that the differences in male plumage must be the result of strong selection pressure at a few key genetic loci.
To find out if this idea was correct, the research group used high-throughput sequencing to compare the genomes from nine capuchino species. The results were conclusive, and offered a unique insight into the genetics of speciation. Ninety-nine per cent of the genome differences occurred in the same small areas of DNA: regions on different chromosomes that are involved in synthesising the melanin-related proteins that give feathers their colour. Most frequently, these changes did not affect the genes themselves, but rather the adjacent non-coding regulatory sequences. The important point is that although the regulatory regions vary from species to species, they control the expression of the same set of genes. Campagna believes that it is the altered expression of these melanin-related genes that underpins the phenotypic variation seen in the capuchinos.12 Also, because speciation occurred so rapidly, it must have resulted from female choice, which in turn caused the males to fine-tune their gene expression very quickly.
While Campagna’s team were collating their data, other groups reported differences in the pigmentation genes from several unrelated pairs of incipient avian species. For example, the different coloured subspecies of the Chestnut-bellied Monarch found on the Solomon Islands result from single amino acid substitutions in two melanin-related genes. The races’ contrasting belly plumages, chestnut versus blue-black, may be sufficient to cause pre-mating isolation and future speciation.13 Similar genetic differences have been reported for the Carrion and Hooded Crows, as well as for the Blue-winged/Golden-winged Warbler complex.14 The importance of all these studies is that genetic alterations in one simple molecular pathway can result in phenotypic changes that have the potential to create new species.
While sexual selection accounts for the capuchinos’ high overall rate of speciation, it does not explain why it should have been greatest to the south of the Amazon. One explanation is that the region was repeatedly and extensively flooded by sea water during the late Pleistocene, and that these events fragmented the early population, leading to isolated groups with little scope for genetic exchange. Also, Jon Fjeldså and Carsten Rahbek believe that the combination of open-habitat refugia and specific niche requirements could have kept small local populations apart in patches of suitable grassland.15 The temperate climate during the last glacial maximum, some 27,000 years ago, resulted in savanna-like habitats throughout South America, while fluctuations in the south polar air currents, as a result of Quaternary glacial changes, led to cycles of reciprocal expansion and contraction of open habitats and rainforests.
As in most taxa, seedeater speciation does not seem to be the result of a single mechanism, but rather of a combination of factors, including sexual selection, marine ingressions and open-habitat refugia.
Darwin’s finches
Darwin’s finches are the most celebrated of all the tanagers and, ever since their discovery, have been a model of speciation and adaptive radiation. Indeed, the species living on the Galápagos Islands (another inhabits Cocos Island, 600 kilometres to the north) are ‘among the most thoroughly studied wild animals in existence’.16 Unlike other young adaptive radiations, such as the Hawaiian honeycreepers, Darwin’s finches are intact, and no species has been lost from human activity. This fact makes the clade especially valuable for understanding the ecological and genetic basis of biodiversity. Despite different body sizes, beak shapes, songs and feeding behaviours, all have evolved from a common grassquit-like ancestor that dispersed from South America approximately 1.5 million years ago. Soon after their arrival, the ancestral population split into two: one branch produced the warbler-finches, the Cocos Finch and the Vegetarian Finch, while the second branch gave rise to a group of ground and tree finches. The result was that species evolved to exploit every available food source: seeds, buds, fruit, insects, pollen, nectar, and even blood (Plate 36).
The two warbler-finches, for example, look and behave like mainland warblers, with very thin and pointed beaks which they use to probe leaves of the Palo Santo trees (Bursera graveolens) to catch small insects and their larvae. Both species (recently split on account of different song, habitat and range) look so unlike finches that Darwin mistook the birds for true warblers.
The Sharp-beaked Ground Finch, however, has a slightly larger and more cone-shaped beak that it uses to collect both insects and small seeds, while the Genovesa Cactus Finch has a relatively robust and elongated beak for penetrating the firm covers of cactus fruits. The largest of all beaks, a massive, extremely deep and broad bullfinch-shaped structure, is possessed by the Large Ground Finch; it uses its beak to crush the large and hard seeds that are not accessible to other species. On two small islands, the Vampire Ground Finch uses its sharp arrow-shaped beak to peck at the wings and tails of boobies to drink their blood. Strangely, the seabirds do not seem to mind, and it is thought that the behaviour evolved from the pecking strategy that the finches used to remove parasites from the boobies’ feathers. This oddly behaving finch also smashes boobies’ eggs against the rocks to obtain the yolk, and drinks the blood of its own dead. In contrast, the Vegetarian Finch uses its broad and stout beak to strip back the bark of small branches to get at the underlying nutritious pulp, while the Woodpecker Finch uses a cactus spine or leaf stem as a tool to extract its prey.
Darwin’s finches exhibit considerable morphological overlap, so that many congeners are difficult to tell apart, not just in the field but even in museum collections. And if that were not enough, recent research has revealed the existence of three additional species based solely on genetic differences. In 2015, Leif Andersson, a geneticist at Uppsala University in Sweden, and his colleagues were the first to sequence the complete genomes of all 14 recognised species.17 When the genomic data were used to construct a phylogenetic tree, the researchers found that what had traditionally been accepted as two species, based on beak morphology, were in fact five species. The Sharp-beaked Ground Finch occupied three entirely different branches of the phylogenetic tree, while the Large Ground Finch sat on two separate divisions. In other words, genomics has shown that there is much more to Darwin’s finches than meets the eye, with no less than 17 identifiable taxa.
One explanation for the number of species is their exceptionally fast radiation, even by tanager standards, one strongly influenced by geography and climate change. All the islands remain isolated, not just from the mainland but also from each other, so that few competitors or predators made the journey, especially during the early years of colonisation. Also, each island varies in height and habitat and supports a unique combination of animals and plants. New islands were formed by volcanic activity, while climatic oscillations caused by the El Niño phenomenon led to changes in the islands’ flora and associated insect life, all of which created a range of different ecological niches. Furthermore, speciation has been facilitated by crossbreeding and the mixing of genes throughout the finches’ evolutionary history. While hybrids of most avian species are sterile, the hybrid chicks of Darwin’s finches are fertile and can mate with both parental species. The resulting offspring will associate with one or other of the parents through song or appearance despite possessing genes from both species. The importance of gene flow or introgression (see The Sparrow’s Story) is that novel combinations of genes can be rapidly created, promoting the emergence of new taxa.
It was Peter and Rosemary Grant, a British husband and wife team now working at Princeton University, who first demonstrated just how fast evolution can operate. The two biologists have devoted their working lives to the study of the Galápagos finches, spending six months every year for over a quarter of a century, capturing and tagging birds, documenting beak and wing measurements, and taking blood samples for genetic analysis. In 1977, following a severe drought, the Grants witnessed a marked reduction in the population of Medium Ground Finches on the island of Daphne Major, due to a shortage of food. At the beginning of the year, the island had over 1,000 individuals, but 12 months later the population had fallen to less than 200. When the survivors were studied, they were found to be slightly bigger than the previous population average, with marginally larger beaks. It appeared that these individuals, unlike their smaller kin, were better able to access the island’s only remaining food source – the big, spiky seeds of the plant Tribulus. Most survivors were male, as females are slightly smaller, and when the rains returned the following year and breeding recommenced, there were five males for every female. In the fierce sexual competition that followed, only the largest males succeeded in breeding, so the genes for larger bodies and beaks were more likely to be inherited. Remarkably, it seems that for the Medium Ground Finch the difference between life and death in times of drought depended on as little as half a millimetre in beak length.
Five years later, the Grants observed climatic changes that would again change the makeup of Daphne Major’s resident birds. This time a prolonged rainy season due to one of the strongest El Niño events ever transformed the island’s vegetation into a community of smaller seed-producing plants that favoured individuals with smaller beaks. The El Niño rains had altered the food supply, and only the smaller-beaked birds won the battle for survival – the opposite of what had happened a few years earlier.
For Peter and Rosemary Grant, the Medium Ground Finch had shown that natural selection can produce morphological changes exceedingly quickly. Indeed, they calculated that it would only take 23 bouts of severe drought to convert the phenotype of the Medium Ground Finch into that of its parrot-billed cousin, the Large Ground Finch.16 Recently, developmental biologists have added a new twist to the Grants’ meticulous field observations. Arkhat Abzhanov, a postdoctoral fellow at Harvard Medical School, studied embryos from six species of finch and determined when and where different growth-factor genes were expressed in the developing beak.18 Three species had large bills for cracking seeds while three species had slender, pointed beaks for extracting nectar. The only protein to distinguish between the two cohorts was bone morphogenic protein 4 (Bmp4), a signalling protein typically associated with the development of the skull and other bones. The two bird groups differed in both the amount and the timing of Bmp4 expression. Those birds with the largest beaks made more protein and at an earlier stage than smaller-beaked individuals, with each species having its unique pattern of expression. Furthermore, artificially increasing the amount of protein, by local injection of a virus which contained the Bmp4 gene, resulted in the beak becoming larger. These preliminary experiments suggest that Bmp4 is important in shaping birds’ beaks, although what makes the growth factor more active in birds with big beaks remains unknown.
Beak development, like most biological traits, is an intricate process and controlled by more than one gene. In 2015, ALX1, a gene known to be involved in human craniofacial development, was also linked to beak shape in Darwin’s finches, specifically to how blunt or sharp the bill becomes.17 Researchers noted two variants or haplotypes of the gene in the birds: an ancestral form associated with pointed beaks, which evolved early, before the group’s radiation, and a derived form that leads to blunt beaks. Individuals with both haplotypes have intermediate bill shapes.
Several months later, the same research team identified a gene linked to beak size rather than shape.19 The gene, known as HMGA2, had previously been associated with variations in height, facial structure and tooth eruption in humans. The role of HMGA2 in beak structure was confirmed after studying survivors from a severe drought that struck the Galápagos Islands in 2004 to 2005. At that time, many of the Medium Ground Finches with larger-than-average beaks starved to death as they were out-competed by a larger species that had recently colonised their island and were better able to eat large seeds. After the drought, the surviving Medium Ground Finches had smaller beaks than those that succumbed, since they were more suited to taking the smaller seeds that their competitors tended to avoid. Even today, the Medium Ground Finch has a smaller beak size than before the drought. By analysing DNA from birds that lived at the time, it was noted that the large-beak HMGA2 variant was more common in the Medium Ground Finches that starved to death, and less common in survivors. In other words, changes at a single locus had facilitated a rapid diversification in beak shape.
Genetic mutations may not be the only molecular factors to explain how species evolve. Epigenetics, which is the regulation of gene function without a change in the genetic code, may also be important. The term ‘epigenetics’ was coined by developmental biologist Conrad Waddington of the University of Edinburgh after he noticed that developing fruit flies exposed to chemicals or temperature changes could be induced to produce different wing structures (epi- means ‘above’, ‘on’ or ‘beside’ in Greek). Although such anatomical changes were induced in a single generation, they were passed on to all subsequent lineages. It seems that Jean-Baptiste Lamarck’s once-ridiculed idea that the environment can directly alter traits that can then be inherited was right after all. Indeed, biologists now understand how such processes may occur. One of the mechanisms involves acquired DNA methylation, in which chemical components called methyl groups (derived from methane) bind to DNA and regulate gene expression. When methyl groups are added to a particular gene, the gene is switched off or silenced, and no protein is produced. Environmental factors, including temperature and stress, can alter the extent of methylation, and these changes may be permanently programmed and inherited over many generations: a process known as epigenetic transgenerational inheritance. Crucially, such genetic modifications can account for the rapid emergence of new traits, events that are difficult to explain solely with classical genetics and neo-Darwinian theory.
Could epigenetics be involved in the evolution of Darwin’s finches? To find out, Michael Skinner, working at Washington State University, undertook a detailed study of the patterns of methylation across the genomes of five finch taxa.20 Not only did each species have a different methylation pattern, but the changes also increased with the phylogenetic distance between each species. There was also minimal overlap of the individual epigenetic sites among the species. Skinner and his colleagues then carried out a more focused study, looking at the methylation profiles of genes known to be involved in the development of beak shape, immune-system responses and plumage colour. Once again, the epigenetic patterns differed for all the gene groups, while the gene sequences were nearly identical.
For almost 200 years, Darwin’s finches have provided us with a unique window into the mechanisms of evolution. But the more they have revealed, the more complex the story becomes. It is now apparent that a full understanding of the molecular control of speciation will require the integration of results from both genetic and epigenetic studies.
Flowerpiercers
The long and at times labyrinthine journey that has taken us from the ancient monotypic ostrich to the most recent and highly polytypic family of tanagers is now nearing completion. After around 100 million years of evolution, and approximately 220 families and over 10,600 species later, we have reached the terminal bifurcations, the outermost twigs and offshoots of our schematic ‘bird tree’. The tanager’s story, however, is not yet complete and promises one more surprise. Eight-and-a-half million years ago, a unique feeding strategy evolved in a group of ancestral Thraupidae living along the northern slopes of the Andean rainforest. It seems that this group abandoned fruit as their primary food source and switched instead to nectar, and in so doing gave rise to the 18 species we know today as flowerpiercers.
The events that led to their dietary change are lost in the mists of time, but it is not hard to imagine a likely scenario. A bird in search of fruit, possibly with a slightly longer bill than usual, may have accidentally pierced the tubular corolla of a nectar-containing flower and so benefited from its sugar-rich food supply. Subsequent generations became ever more dependent on nectar and, as a result, evolved increasingly efficient means of obtaining it. Their tongues developed a ventral groove, with the distal part splitting into a terminally frilled fork, while their bills grew longer and increasingly hooked (Plate 37). These traits allowed the birds to stabilise the flowers while penetrating the nectar-containing bases with their lower jaws and extracting the contents with their tongues. It is this unique combination of bill and tongue that has increased the flowerpiercers’ access to a wide range of nectar sources which remain inaccessible to legitimate, non-robbing, visitors. Biologists regard flowerpiercers as ‘nectar-robbers’, or ‘nectar stealers’, since, unlike hummingbirds, they are not pollinators and provide no benefit to the plant.
The notion that the development of novel morphological features is accompanied by trade-offs is central to current evolutionary theory, although it has been surprisingly difficult to prove in the case of higher organisms. What this means, in reality, is that it is not possible for a ‘superspecies’ to evolve, one that is optimised to do everything, with a high degree of efficiency in all possible situations. But can this thesis be shown to apply to birds? In 2003, Jorge Schondube and Carlos Martinez de Rio, two American biologists, addressed this question by devising a simple experiment using captive Cinnamon-bellied Flowerpiercers.21 They trimmed their bill lengths, with ordinary nail clippers, to mimic the ancestral state – a procedure that did not hurt the birds, as keratinous beaks lack nerve endings and will grow back within a month. They found, as they had conjectured, that birds with clipped bills ingested fruit far more efficiently, but at the expense of a reduced ability to rob flowers. Conversely, birds with intact bills were good flower robbers, but poor frugivores.
The phylogenetic relationships of the flowerpiercers have long puzzled ornithologists, and it is only after the availability of mitochondrial DNA sequence data that their position within the tanager family has been proven. Furthermore, the seminal study on their phylogenetics, conducted by Kevin Burns and William Mauck at the San Diego State University, has also shed light on the complex mechanisms that underpin their diversification, processes that we have met and discussed previously: Andean uplift, habitat change, climatic cycles and tectonic activity.22 The main mountain-building processes in South America occurred between 7 and 4 million years ago, while further and more rapid Andean uplifts took place as recently as 2 million years ago. Intriguingly, these dates correspond well with the molecular timing of many flowerpiercer speciation events. Also, several early dispersals occurred from out of the Andean founder population: one to Central America, giving rise to two species, the Cinnamon-bellied Flowerpiercer and the Slaty Flowerpiercer, and at least one to the tepuis, the isolated table-top mountains scattered throughout the rainforests of Venezuela.
Glossy images of the best-known tepuis adorn tourist brochures, and uniquely convey the region’s beguiling beauty and remoteness from our everyday experience. The largest, Auyán-Tepui, boasts the world’s tallest waterfall, Angel Falls, which plummets nearly a kilometre to the forest floor, while the highest, the mystical 2,810-metre Mount Roraima, is the most accessible and lies at the triple border point of Venezuela, Guyana and Brazil. There are well over 100 tepuis, all relics of a vast sandstone plateau, stretching from the Andes to the Atlantic coast, that became eroded during the Cretaceous and possibly as late as the Quaternary. It now seems that the ancestors of two species, the Greater Flowerpiercer and the Scaled Flowerpiercer, reached the tepuis before much of this erosion had taken place when the habitat was more or less continuous with that of the Andes. Subsequent geological processes marooned these avian wanderers amid a sea of open savanna, and with no further opportunities for gene exchange, they evolved into separate species. Such scientific conclusions, based on the latest molecular techniques, had already been envisioned by the Scottish author Sir Arthur Conan Doyle. His popular novel The Lost World (1912) presciently depicts the tepuis’ flora and fauna as remnants of ancient life forms, albeit dinosaurs, prehistoric reptiles and ape-men.23
As I stare at my computer screen and guide the cursor for the final time over the spiral-like graphics of the avian tree of life at www.onezoom.org, the terminal offshoot, bearing the very last leaf, comes into focus. Its blank green ovate form, once enlarged, informs me that 128,300 years ago the Grey-bellied Flowerpiercer diverged from the rest of its genus: a rather small and unobtrusive bird to occupy such a noteworthy place in our story. An endemic of Bolivia and northern Argentina, it is fairly common above 2,500 metres, being found in montane woodlands, scrub and gardens, where it feeds on fuchsia and other flowers.
I’ll vouch that most visitors, strolling along the paths of La Paz’s botanical gardens, will be unaware that the distinctive song issuing from a nearby epiphyte is that of a male Grey-bellied Flowerpiercer, a species that belongs to evolution’s most recent avian lineage. Nor, I suspect, will they be cognisant of his impressive pedigree, a bird whose ancestors survived the Chicxulub impact, reached Australasia following the break-up of Gondwana, dispersed from the Old to the New World via Beringia, to become the latest line in the myriad of oscines that today populate the Neotropics. His rapid, jumbled warbling is delivered to attract a mate and so ensure that his genetic makeup, honed by millions of years of natural selection, is passed to the next generation and that the process of evolution continues – an unbroken chain of neornithine genetic causality that stretches from tinamou to tanager.
Now, that is what I call an ascent.