Tropical islands are home to a wide variety of unique and exotic bird species. The warm climate, abundance of fruit and insects, and lack of predators on many islands allows different types of birds to thrive. Some birds are endemic to specific islands or island chains, while others are more widespread throughout the tropics. But what are some of the most common types of birds found on tropical islands?
Seabirds
Many tropical islands are home to numerous seabird species that nest on the islands and use the surrounding oceans for feeding. Some examples include:
- Frigatebirds – Large, black birds known for the balloon-like red pouches on their throat. They have an impressive wingspan of up to 7 feet. There are 5 species of frigatebird found on tropical islands globally.
- Boobies – These are large seabirds named for their clumsy landings. They have brightly colored feet and come in different species like the Blue-footed Booby, Red-footed Booby, Masked Booby, etc. They are found across the tropics.
- Tropicbirds – Slender white birds with exceptionally long tail feathers. There are 3 species (Red-billed, White-tailed, and Red-tailed) found on tropical islands.
- Noddies – Smaller tern-like birds that nest in large colonies on tropical islands. The Brown Noddy is the most widespread species.
- Other terns – Terns are coastal seabirds that plunge-dive for fish. Common tropical species include Sooty Terns, Bridled Terns, Crested Terns, etc.
- Shearwaters – Medium-sized seabirds named for their gliding flight pattern. Audubon’s Shearwaters and Wedge-tailed Shearwaters are examples of tropical species.
These seabirds nest on tropical islands to take advantage of a lack of predators, ample nesting habitat, and proximity to rich ocean feeding grounds. Islands along the equator provide a constant food source as warm tropical waters have high marine biodiversity.
Land birds
While seabirds dominate the avian populations on many remote tropical islands, there are also a variety of resident land bird species. Some examples include:
- Parrots – Tropical islands are the perfect habitat for parrots which feed on fruits, nuts and seeds. Some island species include the Puerto Rican Amazon, Imperial Amazon, and the extinct Carolina Parakeet.
- Doves – Smaller peaceful doves can flourish on tropical islands where they don’t have to compete with as many other bird species. Examples are the Zenaida Dove and Peaceful Dove.
- Kingfishers – These brightly colored fish-eating birds occupy many ecological niches on tropical islands. The Belted Kingfisher is a widespread tropical island species.
- Hummingbirds – There are over 300 species of these small, fast flying nectar birds worldwide with many endemic to tropical islands.
- Honeycreepers – This is a family of small finch-like songbirds adapted to tropical climates. Hawaii has over 20 species of honeycreeper found nowhere else.
- Cuckoos – Tropical and subtropical cuckoos are often found on remote tropical islands. The Pheasant Cuckoo and Mangrove Cuckoo are examples.
- Rails – secretive marsh birds that live in dense vegetation. Island species include the Guam Rail, Lord Howe Woodhen, and Tahiti Rail.
These are just a few examples of the many types of land bird species that can evolve into unique endemic species on isolated tropical islands. Lack of predators and competition allows them to fill specialized niches.
Migratory birds
In addition to resident species, many migratory birds either winter on tropical islands or stop over during migration between breeding and wintering grounds. The most common migratory island birds include:
- Warblers – diverse songbirds that migrate huge distances. Northern waterthrush and American redstart are common overwintering warblers.
- Shorebirds – waders like plovers, sandpipers, stilts that stop to rest and feed on coastal islands during migration.
- Petrels – pelagic seabirds like the Black-capped Petrel that breed on northern islands but winter around tropical islands.
- Terns – arctic breeding terns like the Common Tern and Arctic Tern stop at tropical islands during their pole to pole migrations.
- Osprey – these fishing raptors breed in temperate regions but winter along tropical coasts.
The resources available on tropical islands make them important stopover or wintering grounds for migratory species traveling huge distances every year between breeding and non-breeding territories.
Introduced species
Over the centuries, humans have intentionally or accidentally introduced many non-native bird species to tropical islands that have established breeding populations. Some common examples include:
- Chickens – domestic chickens brought for food have gone feral on many islands.
- Cattle Egrets – now found across the tropics, they hitched rides in cattle boats from Africa.
- House Sparrows – one of the most widespread invasive bird species worldwide.
- Rock Pigeons – this classic city bird has been introduced to urban areas on tropical islands.
- Common Mynas – these aggressive Indian mynah birds compete with native island species.
- Eurasian Collared-doves – now found across the Caribbean after an accidental release.
Invasive species can threaten native island birds through direct competition for food and habitat or predation. Controlling introductions is important to protect endemic species.
Extinct island birds
Due to their isolation and evolution in the absence of predators, many island bird species were highly vulnerable to introduced predators and human activity. Sadly, this has led to disproportionately high extinction rates for island birds. Some examples of now extinct tropical island birds include:
- The Dodo – this famous flightless pigeon lived on Mauritius before going extinct in the 1600s.
- Stephens Island Wren – endemic to a tiny New Zealand island before being wiped out by a single cat in 1894.
- Hawaiian Oo – several species of these nectar-feeding Hawaiian honeyeaters were wiped out following Polynesian settlement.
- Jamaican Red Macaw – this Caribbean parrot was declared extinct around 1800 due to hunting and habitat loss.
- Passenger Pigeon – this migratory species once numbered 5 billion birds but was hunted to extinction by 1914.
- Carolina Parakeet – this mainland U.S. parrot also ranged down into the Caribbean before going extinct.
Today, conservation efforts on many tropical islands aim to protect endemics from suffering the same fate while working to control invasives. Protecting rare island ecosystems supports unique birdlife.
Key factors influencing tropical island birds
There are several key factors that influence which bird species are found on tropical islands:
- Isolation – more distant islands have higher rates of endemism as birds evolve into new species over time.
- Habitat diversity – islands with a mix of habitats like forests, shrubland, wetlands, and beaches support more species.
- Food availability – fruit, seeds, insects, fish, and nectar allow different birds to thrive.
- Size – larger islands have more species as they can support bigger populations.
- Invasive species – predators and competitors introduced by humans threaten native birds.
- Severe weather – hurricanes and droughts naturally impact populations.
- Human activity – habitat loss, hunting, and pollution endanger birds.
Balancing these factors allows a wide array of species to persist while extinction threats must be mitigated through habitat protection and invasive species control.
Unique island bird behaviors
The behaviors of some tropical island birds are quite different from mainland relatives due to a lack of predators and human pressures:
- Ground nesting – with few land predators, many seabirds nest right on the ground in large colonies.
- Flightlessness – with no predators some island birds like rails have lost the ability to fly.
- Tameness – island species unused to humans can be extremely approachable.
- Loss of seasonal behaviors – seabirds may forego migration remaining near islands year round.
- Colonial nesting – in parasite free habitats some birds nest densely in mixed colonies.
- Rapid evolution – isolated islands allow rapid divergence into multiple endemic species.
Understanding these behaviors provides insight into how birds adapt to predator-free island environments over time.
Unique island adaptations
Island birds also evolve unique physical and behavioral adaptations including:
- Smaller size – island food webs support smaller birds with reduced competition.
- Larger size – some raptors get bigger to adapt to available prey.
- Plumage changes – loss of camouflage and bright colors in the absence of predators.
- Specialized bills – adaptation of beak shape and size to different food sources.
- Song differences – isolation leads to unique songs and calls.
- Clutch size – some island birds lay fewer eggs than mainland relatives.
- Foraging behaviors – feeding strategies evolve to utilize island resources.
Studying endemic island birds provides great insights into evolution and adaptation in isolated island environments over long timespans.
Conservation of island birds
Many tropical island birds face serious threats today unfortunately:
- Habitat loss from development, logging, agriculture, etc.
- Invasive species that compete with or prey on native birds.
- Overexploitation from hunting and egg harvesting.
- Diseases spread by introduced species.
- Severe weather exacerbated by climate change.
- Pollution and pesticides in the marine food web.
Several approaches can help conserve threatened island birds:
- Habitat protection in reserves safe from exploitation.
- Eradication of invasive predators from islands.
- Captive breeding and reintroduction programs.
- Sustainable development that protects ecosystems.
- Control of wildlife trade in threatened species.
- Community engagement and education.
- Research and monitoring of populations.
With proactive conservation efforts, the fascinating birds that evolved on tropical islands over millennia can continue thriving in these unique island ecosystems.
Conclusion
Tropical islands are home to an incredible diversity of endemic birds evolved over millions of years in isolation. Seabirds dominate thanks to plentiful marine food resources and island nesting sites safe from mainland predators. Meanwhile parrots, doves, rails, and songbirds adapted to fill specialized niches on tropical islands and evolve into unique species. Migratory birds make use of islands for wintering or migration stopover habitat. However, human impacts have caused disproportionately high extinction rates for island birds. Protecting habitats from development and invasive species while fostering sustainable lifestyles will be key to conserving these fascinating and beautiful island species into the future.