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Avian biogeography

Avian biogeography

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Avian biogeography

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  1. CHAPTER 2 Avian biogeography

  2. Why study biogeography of birds ? • Different aspects of avian biology addressed • how have new bird species arisen ? • how did they come to be distributed in the way they are ? • how are patterns of distribution and diversity maintained ? • how does their (behavioural) ecology differ between regions?

  3. Why study biogeography of birds ? • Birds as ecological model • evolutionary relationships well understood

  4. Why study biogeography of birds ? Birds as ecological model

  5. Why study biogeography of birds ? Birds as ecological model Irwin et al. 2001. Speciation in a ring. Nature 409: 333-337

  6. Why study biogeography of birds ? • Birds as ecological model • evolutionary relationships well understood • geographical pattern of morphological variation well studied • distributional patterns well mapped

  7. Why study biogeography of birds ? Birds as ecological model Opisthocomus hoazin

  8. Why study biogeography of birds ? • Birds as ecological model • evolutionary relationships well understood • geographical pattern of morphological variation well studied • distributional patterns well mapped • high mobility allows presence and radiation on remote islands • very strong seasonal migration • large-scale ringing data

  9. Continental birds

  10. Continental birds • level of distinctiveness of land-masses reflects both their relative position and geological history (tectonics, duration and degree of isolation, opportunities for separate evolution)

  11. Continental birds Archaeopteryx – ca 150 Geological time scale and break-up of Gondwanaland

  12. Continental birds • level of distinctiveness of land-masses reflects both their relative position and geological history (tectonics, duration and degree of isolation, opportunities for separate evolution) • combination of present distribution patterns along with palaeo-geological evidence • 19th century: global system first developed for passerine birds, then modified by Alfred Russel Wallace (1876) to apply to animals in general • crucial barriers are seas, deserts, mountain ranges, climatic-vegetation ecotones

  13. Continental birds Main biogeographical regions of the world

  14. Continental birds Main biogeographical regions of the world

  15. Continental birds Main biomes (vegetation zones) of the world

  16. Continental birds • proportions of families, genera and species shared depend on the effectiveness of the barriers and the distances between the regions, both now and in the geological past • the longer an area has been isolated, the higher the taxonomic rank of its endemics

  17. Continental birds Palaearctic region Palaearctic region

  18. Continental birds • Palaearctic region • 46 mil km²; more than twice as big as any other region • within each type of habitat, more species at E than W end of Eurasian land-mass, due to the greater severity of the glaciations in the west

  19. Continental birds • Palaearctic region • 46 mil km²; more than twice as big as any other region • within each type of habitat, more species at E than W end of Eurasian land-mass, due to the greater severity of the glaciations in the west • marked seasonality

  20. Continental birds • Palaearctic region • Atlantic has proved an effective barrier to range extension in landbirds: Northern wheatear, Cattle egret, Little gull, Fieldfare, Spotted sandpiper, Wilson’s phalarope

  21. Continental birds • Palaearctic region • Bering Strait: dry land during glacial periods (10.000 y ago) and holds series of islands (stepping stones): Yellow wagtail, Northern wheatear, Arctic warbler, Snow goose, Grey-cheeked thrush, Yellow-rumped warbler (tundra or boreal forest)

  22. Continental birds • Palaearctic region • Mediterranean Sea ca 5 mil y (early Pliocene); less effective barrier with many islands: North African species are Palaearctic in affinity (e.g. 165 species breeding but not extending in sub-Saharan Africa): Dupont’s lark, Moussier’s redstart, Tristram’s warbler, Algerian nuthatch supplemented by Sub-Saharan species (White-rumped swift, Black-crowned tchagra)

  23. Continental birds • Palaearctic region • birds of N and C Sahara predominantly Palaearctic, mainly at oases (Cirl bunting, Eurasian spoonbill, Little owl) supplemented by Afrotropical species extending N (Small buttonquail, Red-knobbed coot, Little green bee-eater, Senegal thick-knee, Nile valley sunbird)

  24. Continental birds • Palaearctic region • mountainous southwest Arabia usually included in Afrotropical Region, while birds of Persian Gulf and Iran predominantly Palearctic

  25. Continental birds • Palaearctic region • mountainous southwest Arabia usually included in Afrotropical Region, while birds of Persian Gulf and Iran predominantly Palearctic • at least 937 landbird species breed regularly in the Palearctic Region, which is a low number and a low level of endemism (no endemic families, 9% genera and 47% species restricted to the region)

  26. Continental birds • Palaearctic region • localised endemics at Madeira, Canary Islands, Cyprus, Azores, Corsica and Caucasus

  27. Continental birds Palaearctic region Palaearctic region

  28. Continental birds • Palaearctic region • within both regions, proportion of shared species increase N, resulting in a Holarctic distribution: e.g. Red crossbill, Northern goshawk, Common goldeneye (boreal forest); Rock ptarmigan, Gyr falcon, Lapland longspur (tundra); King eider, Sabine’s gull, Glaucous gull (arctic ocean)

  29. Continental birds • Palaearctic region • closely related species point towards recent divergence in geological time (ancestral homes differ between pairs); e.g 0.5 mil y for Northern harriers; 4.3 mil y for Eagle owls; 7.9 mil y for Pygmy owls

  30. Continental birds Ecologically equivalent and closely related species in Eurasia and North America

  31. Continental birds • Palaearctic region • some families poorly represented, such as 7 and 2 species of Kingfishers (86 species) and 1 and 2 species of Parrots (360 species) • examples of poorly represented Old World families in North America are Warblers, Shrikes and Larks, and the representatives are often more closely related to eastern Asian species • examples of poorly represented New World families in Eurasia are Wood warblers; Tyrant flycatchers and Vireos

  32. Continental birds • Palaearctic region • migrant passerines in both regions are phylogenetically more different from each other than the residents and short-distance migrants • suggests that many long-distance passerine migrants (mainly insectivorous warblers and flycatchers) derived from essentially tropical families • not true for shorebirds and waterfowl

  33. Continental birds Indomalayan (Oriental) region

  34. Continental birds • Indomalayan (Oriental) region • 9.6 mil km²; mainly within the tropics; northern border (Himalayas) corresponds with climate-vegetation ecotone • includes Indonesian archipelago, Philippines, Borneo, Sulawesi, Sumatra, Java and Bali • transition zone between Oriental and Australian Regions called Wallacea; 120 m lower sea level during glaciations, when Sunda shelf was connected to continental Asia; deep water channel east of Sunda shelf contains oceanic islands such as Moluccas and Lesser Sundas

  35. Continental birds Boundary between Indomalayan and Australasian faunas

  36. Continental birds • Indomalayan (Oriental) region • not known till when Philippine Islands were attached to SE Asia, Sulawesi may never have been connected to mainland Asia; more avian affinities with Philippines and Lesser Sunda Islands than with Sumatra and Borneo • 3rd richest Region with 1697 species; 3 endemic families (Leafbirds, Asian frogmouths and Bearded bee-eaters), 129 endemic genera, 1184 endemic species (70%)

  37. Continental birds Indomalayan (Oriental) region

  38. Continental birds • Indomalayan (Oriental) region • major wintering area for east Palaearctic breeding birds • shares most families (but not species) with Africa, probably because of connection by broad stretch of tropical habitats through Middle East till Miocene (often considered single Palaeotropical Region for plants)

  39. Continental birds • Indomalayan (Oriental) region • at family level both regions share Broadbills, Bulbuls, Sunbirds, Weavers, Honeyguides • family Phasianidae particularly well represented, and centre of radiation for Pittas, Laughing thrushes, Drongos, Flowerpeckers

  40. Continental birds Indomalayan (Oriental) region

  41. Continental birds • Indomalayan (Oriental) region • richness partly results from fusion of 3 separate faunas originating at different land-masses, and infiltration from at least 2 others; some regions isolated for long periods; inclusion of many islands (e.g. Philippines 7100 islands) with high endemism (Philippines: 43% of 403 breeding species endemic; Sulawesi 36% of 247 species) • strong difference between SE part of Eurasia and rest of land-mass due to effectiveness of Himalayan chain and Tibetan plateau, abundance of islands, and tropical forest belt

  42. Continental birds Afrotropical (Ethiopian) region

  43. Continental birds • Afrotropical (Ethiopian) region • mainly tropical region; south of the Sahara and Madagascar, Comoro, Seychelles and Mascarene Islands (islands sometimes separated as a distinct Malagasy Region) • northern border poorly defined across Arabia • ca 21 mil km² (1.25 mil south of tropics)

  44. Continental birds • Afrotropical (Ethiopian) region • main vegetation types run in latitudinal belts, becoming more arid and open north- and southwards from the equator, but basic pattern is complicated by topography • markedly seasonal climate with distinct dry and wet seasons

  45. Continental birds • Afrotropical (Ethiopian) region • although similar in latitude as Neotropical Region, it contains less than half as many landbird species (ca 1950 regional breeders), partly because tropical and montane forest cover much smaller areas and high arid plateaus are more extensive

  46. Continental birds • Afrotropical (Ethiopian) region • among passerines, Weavers, Waxbills, Starlings, Larks, Shrikes and Sunbirds are especially well represented. Also rich in Francolins, Bustards, Barbets, Honeyguides and Cisticola’s, but poor in Parrots and Woodpeckers.

  47. Continental birds • Afrotropical (Ethiopian) region • both species of Oxpecker have evolved in close association with large herbivorous mammals

  48. Continental birds • Afrotropical (Ethiopian) region • 11 endemic families of mainland Africa and 6 of Malagasy mostly contain small numbers of species, and some are represented among fossils from Europe and North Africa

  49. Continental birds • Afrotropical (Ethiopian) region • main centres of endemism: Ethiopian massive, Cameroon Mountains, East African Mountains, Somali and Namibian arid zones, Gulf of Guinea Islands (Principé, São Tomé)

  50. Continental birds • Afrotropical (Ethiopian) region • hard to decide in which direction colonization took place, but some seem certain: e.g. two African Pittas, four African Broadbills, eight African Drongos (from SE Asia); three African Wagtails, Longbilled pipit (from Eurasia); Cisticolajuncidis, Ploceus weavers, Estrildinae (to SE Asia) • enormous influx from Palaearctic migrants (about a third of all species from that region), some species occasionally breed in Africa