True Finches revealed.

Mention Finches and all birders know what you mean – or do they? Seven families (Fringillidae, Estrildidae, Emberizidae, Thraupidae, Ploceidae, Passeridae and Cardinalidae) contain about 1000 species which I call Finches or Finch-like birds. You can see more about these birds by clicking on http://baob.wikidot.com/finch-like-birds.

The ones I am talking about here are called “True Finches” and are listed in family Fringillidae. The way they evolved and developed is in interesting story so I thought I would share it with website visitors.

The birds considered here account for 146 species and include Chaffinch, Brambling, Serin, Canary, Citril, Seedeater, Siskin, Greenfinch, Goldfinch, Rosefinch, Redpoll, Linnet and Crossbill. (I exclude Euphonias and Chlorophonias which tend to be considered as a separate sub-family). They are widely distributed and are found in a variety of habitats ranging from grassland, open woodland, elevated woodland and forest to arid, desert areas.

Over the last ten years or so quite a few scholarly articles about the evolution and development of Fringillidae species have appeared on the internet. Understandably but unfortunately much of this work is reported by specialists in the field for an audience who are themselves specialists. Hopefully my review will be meaningful and interesting to birders in general.

Family Fringillidae.

The following table summarises the information I have been able to find in relation to birds listed in family Fringillidae. The time period is expressed in million years ago (mya).

Time (mya) Evolutionary Event

16.5 Fringillidae finches’ radiation following large Himalayan and Tibetan Plateau uplift, triggered by the Indian tectonic plate collision.

14 Rosefinches evolving – followed by a number of radiations.

14 to 12 Common Rosefinch and Scarlet Finch diverged.

12 Genus Pinicola, Pine Grosbeak and Crimson-browed Finch, diverged from their relatives but I don’t know what they were. The Pine Grosbeak became the ancestor of Bullfinches in genus Pyrrhula.

11 to 10 Long-tailed and Streaked Rosefinches diverged.

9 Ancestor of all Greenfinches and probably of Mongolian, Trumpeter and Desert Finches in Afro/Asia evolved.

9 Serins & Canaries in genus Serinus radiating in Africa and Eurasia.

8 Redpolls and Crossbills diverged from a common ancestor.

6.6 Mongolian and Trumpeter Finches evolving.

5 American Goldfinch radiation started.

5 Citril Finch gave rise to European Goldfinch.

3.5 Siskin radiation started in South America.

2.7 Siskin radiation started in North America.

2.6 European and Grey-capped Greenfinches in Africa.

1.1 Grey-capped and Black-headed Greenfinches in Asia.

1 Chaffinch ancestors in Iberia and Morocco colonising Azores, Madeira and Canaries.

Environmental events.

Two major events occurred during the above period of time; one was a major land-mass movement and the other was a climatic change. Both are important to the understanding of their effects on the evolutionary development and survival of bird species in the areas where these events took place..

Land-mass movements.

As part of the break up of the land mass Gondwanaland about 90 mya the Indian Plate split from Madagascar and began moving north. A fragment of the Indian plate initiated a "soft collision" between the Greater Himalaya and Asia about 50 mya. This was followed by the "hard collision" between India and Asia occurred at about 25 mya. This collision with the Eurasian Plate along the boundary between India and Nepal formed the belt that created the Tibetan Plateau and the Himalayan Mountains.

This upheaval of the environment and habitats of birds in this region may well have triggered the adaptive radiation and speciation events which are listed above.

Climate change.

About 2.6 mya the ice sheets in the Northern Hemisphere began to spread. This was the start of the Pliocene-Quaternary glaciation. Since that time the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods. The last glacial period ended about 10,000 years ago.

Areas of glaciation would obviously impact on the habitats and movements of birds in the areas concerned.

Fringillidae evolutionary events.

In the following sections I review these events in three time periods:-
• 16.5 to 9 mya.
• 9 to 2 mya.
• 2 mya to present day.

16.5 to 9 mya.

Rosefinches, Rosy Finches, Mountain Finches and Oriole Finch. (14mya).

It appears likely that the ancestor of these seed eating birds originated subtropical or tropical, moist, evergreen, montane forests of the Afro / Asia regions of the Old World. It would have been in existence at least 14 mya.

The Oriole Finch is a possible candidate. It was part of a radiation which started 23 to 25 mya which ties in with the timing of the Tibetan Plateau and the Himalayan Mountain land-mass movement mentioned above. This timing also fits in with the availability of grass and plant seeds which came into prominence in the period 30 to 25 mya.

There have been a number of Rosefinch radiations. First to split off were the Common Rosefinch and the Scarlet Finch. They are birds of Europe found temperate forests in the Himalayan region. Thought to be related they diverged about 14–12 mya. The Long-tailed Rosefinch, closely allied to the Streaked Rosefinch and possibly other species, diverged around 11–10 mya.

A rosefinch species is believed to have migrated westwards to become the ancestor of the North American Rosy Finches. All these birds live in an alpine or tundra environment and are very environment-specific. In the summer their breeding habitat is rocky islands and barren areas on mountains from Alaska to the North-western USA. These mountain breeding areas tend to be snowfields and rocky scree.

The Grey-crowned Rosy Finch has a wide range and large numbers are found throughout Alaska, and western Canada and the United States. A small number of Gray-crowned Rosy Finches winter on the mainland in South-Central Alaska.

Pine Grosbeak, Crimson-browed Finch and the Bullfinches. (12 mya).

Also diverging from their relatives (I don’t know what they were) about 12 mya were the Pine Grosbeak and Crimson-browed Finch in genus Pinicola. The Pine Grosbeak became the ancestor of Bullfinches in genus Pyrrhula.

These genera evolved in the interior of Asia and the original Pinicola stock was probably a conifer forest bird living to the north of the Himalayas. The separation of the modern species is likely the result of climate change which displaced the Pinicola habitat to sub-arctic northern and sub-alpine Himalayan regions.

At the same time, the evolutionary radiation of Pyrrhula throughout Eurasia and the expansion of the closely related Mountain finches and relatives began.

The Pine Grosbeak is also found in North America. It is possible that their ancestors were wind-blown individuals which arrived via the northern Pacific.

9 to 2 mya.

Desert Finch, Greenfinches. (9 & 6 mya).

The common ancestor of the Desert, Mongolian, Trumpeter Finches and all the Greenfinches probably evolved in Afro / Asia around 9 mya.

Genetically the Desert Finch, which appears to have evolved 6 mya, seems quite close to the common ancestor of the Greenfinches. It thrives in Asian deserts, but could have also inhabited African deserts. It is found in desert areas where water is nevertheless available, but it can also be found in low mountains and foothills, and in cultivated valleys. It feeds on seeds and the occasional insect.

Greenfinches probably originated in Eurasian desert margins coming from the Desert Finch or an extinct, pale plumage, ancestor. It later acquired the green plumage associated with the woodland niche in which the Greenfinches are now found.

Later radiations produced the European and Grey-capped Greenfinches in Africa
about 2.6 mya and the Grey-capped and Black-headed Greenfinches in Asia about 1.1 mya.

Serins and Canaries, Redpolls and Crossbills. (9 – 8 mya).

At about the same time as the Greenfinch ancestor was evolving the Serins & Canaries in genus Serinus were radiating in Africa and Eurasia. Serins of Europe, Africa and Asia (9) and the Canaries of Africa (15) all show some preference for higher and sometimes rocky elevations. Various species are associated with oak, pine, spruce, alder and birch.

Shortly after (8 mya) the Redpolls and Crossbills, which had a common ancestor, began to evolve. The Redpolls (2) are tree dwellers which favour high elevations. The Arctic Redpoll breeds in the Tundra birch forests. The Crossbills of Europe, Asia and the Americas (5) have evolved with different beaks to take seeds from larch, pine and spruce conifers.

Citril Finch, Siskins and American Goldfinch. (5 mya).

Evidence suggests that the Citril Finch is the ancestor of the Eurasian Goldfinch and that this speciation event took place in the Mediterranean region about 5 mya.

The Eurasian Siskin is very common throughout Europe and Asia. It is found in forested areas, both coniferous and mixed woodland where it feeds on seeds of all kinds, especially of alder and conifers. I don’t know just when it evolved but it was probably about the same time as the Greenfinches.

This bird is believed to have reached America either from Asia or from Europe. It is the parental species of the Black-capped Siskin, Pine Siskin and Antillean Siskin of North America. The Black-headed Siskin of Middle America is the ancestor of the South American Siskins

It seems possible that the American Goldfinch, which started radiating 5 mya, also originated from the Eurasian Siskin.

Siskin Radiations. (3.5 mya).

So we have one group of Siskins in Europe and Asia and another two groups in North America and South America.

The South American group began radiating 3.5 mya and the North American group followed 2.7 mya.

2 mya to present.

Chaffinch and Brambling.

The IOC listing recognises two species of Chaffinch and the Brambling. The Chaffinches of Europe and Africa eat seeds and insects. In alpine birch forests of Scandinavia the Brambling is abundant and displaces the Chaffinch. It also likes beech woods where beech mast and hornbeam nuts are an important winter food for this bird. The two Chaffinches are sister species, and the Brambling is sister to the two Chaffinches.

I have not found out when these birds evolved but it must have been before 2 mya and it seems likely that they evolved from Serins and Canaries which were in existence 9 mya.

During the Pleistocene epoch, 2 mya through 10,000 years ago, mean-annual temperatures decreased relative to earlier geological periods. In the Northern Hemisphere glaciers formed and presented barriers to movement which caused populations to be isolated one from one another.

Studies suggest that resident populations in Iberia, Corsica, Greece, and North Africa were not glaciated and that these regions served as refugia for the Common Chaffinch.

Subsequently about 60,000 years ago the various European populations began diverging and the Common Chaffinch colonized the Atlantic islands (Azores, Madeira, and Canaries) from North Africa and or Europe. The island populations are characterized by blue dorsal plumage and reddish-orange breasts, similar to the North African populations.

Physical evidence indicates that islands species evolved larger body mass, longer legs and bills, but shorter wings than their continental relatives. Beak depth and width had increased on the Azores but not on the Canaries. The greatest shift in morphology was observed in birds from the Azores, which had evolved toward the phenotype of the larger Blue Chaffinch.

Concluding Remarks.

In my opinion this review provides a reasonable description of how a quite large group of birds in one family evolved and developed and are now well distributed in Europe, Afro /Asia and America. It all happened quite fast in a relatively short time period from say 15 mya to the present time.

I find it rather satisfying to see the strong connections between various environmental events and the evolutionary processes taking place:-

• The time link between seed availability and the evolution of seed eaters.
• The link between major land-mass movements and speciation events.
• The influence of climatic changes which led to sub-speciation events caused by isolation of various populations.

Evolutionary developments are still taking place associated with various Chaffinch phenotypes, about which perhaps more later. I would also like to find out more about the ancestral links (pre 16 mya) which led to the Fringillidae family development.

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