Transcript Bird biogeography, 9..

Of the approximately 9200
species of birds, only about 290
are marine species although land
only covers about 29% of the
globe
Palearctic region
• Largest
• East-west mountain ranges
• Diverse in climates and habitat although
much of the region is very cold
Birds of Palearctic
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1026 species
Birds may have evolved in this region
Most birds are migrants and insectivorous
One endemic family, Prunellidae
Shared species
• 12.5% with Nearctic
• 15% with Ethiopian
• 22% with Oriental
Palearctic and Nearctic form
Holarctic region
• Loons, auks, grouse found only in these
two regions
Nearctic region
• Also cold
• North-south mountains
Birds of Nearctic
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740 species
Most birds are migrants and insectivorous
Many wood-warblers and blackbirds
No endemic families although
Meleagrididae (wild turkey) is close to
being endemic
Origins of Nearctic birds
• Some are unknown—wrens, warblers,
vireos, sparrows
• Some from Palearctic by way of the Bering
Strait—pigeons, owls, thrushes
• Some from Neotropical region—
hummingbirds, flycatchers
Neotropical region
• 70% of land surface is low elevation and
with abundant moisture
• 32% of South America is tropical rain
forest (only 9% of Africa, 4.5% of Australia)
• 38% of South America is savanna
Birds of Neotropical
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3300 species
Many suboscines, as opposed to oscines
About 31 of 95 families are endemic
Some species emigrated from the Nearctic,
including pigeons, jays, blackbirds, warblers
Ethiopian region
• Less climatic variability than other regions
• Receives only half the rainfall of the
Neotropical region, hence there are more
deserts, grasslands, savannas
Birds of Ethiopian region
• 1556 species
• Many seed-eating and ground-dwelling
birds
• Many weaverbirds, larks
• 6 endemic or nearly endemic families
Oriental region
• Smallest region
• Much of it is tropical and subtropical
• Much rain
Birds of the Oriental region
• 960 species
• Most shared species with the Ethiopian,
Palearctic and Australian regions
• Two endemic families
Australian region
• Diverse climates although much of the
region is dry
• Isolated region
Birds of the Australian region
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906 species
No woodpeckers
Parrots and doves are important groups
13 endemic families
Birds may have originated in the
Holarctic
• Therefore areas separated from the
Holarctic by substantial barriers, e.g.
Australia, sub-Saharan Africa,
Madagascar, and South America tend to
have more endemic taxa than areas less
isolated from the Holarctic
Tropical vs. Temperate Birds
• Many more studies on temperate birds
• I will be presenting generalizations
Tropical vs. Temperate
Environments
• Less seasonality due to temperature
differences
• Instead, wet and dry seasons
• Many tropical food resources are available
year-round
Population ecology of tropical birds
• Breeding seasons longer and more
variable
• Less synchrony within a population
• Breeding seasons not always driven by
food availability
• Fewer available mates in tropical systems
With fewer available mates in
tropics:
Fewer EPCs
Smaller testes
Song output consistent year-round
Sexes tend to be monomorphic
Because tropical birds maintain
territories year-round
• Territories are much larger than for
temperate species
• Population sizes much smaller
• However, keep in mind that 1/3 of tropical
birds don’t have conventional breeding
territories
Other patterns:
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Nest predation higher
Adult survival higher
Clutch sizes lower
More cooperative breeders
Many species are less active
Tropical vs. temperate communities
• More species-rich
• More fruit-eaters, nectar-eaters, ant swarm
followers, large insect eaters (more guilds)
• Many bigger birds in tropical areas
• More species per guild
• Mixed-species flocks year-round
• More suboscines
Tropical community characteristics
• Highest diversity within forest, not at
edges
• Many intra-tropical migrants that are
nectar or fruit-eaters
• Fruit and nectar-eating birds more colorful
than insectivores