Birds in Plant and Environmental Health: Notes

Birds in Plant and Environmental Health

• Birds are indicators and ecosystem architects.
• Presented by Anthony Young.

Key Points

• Birds are critical to the Earth’s ecosystems.
• Humans have extinguished many species.
• Many bird species are critically endangered.
• Bird numbers are falling due to:
  • Habitat loss
  • Changing climate
  • Food source losses
  • Plastic pollution
  • Overfishing
  • Diseases
  • Egg-collecting
  • Predation by humans, pigs, rats, etc.

Birding Credentials

• The presenter has been interested in birds for a long time.
• Received first bird book at age 12.
• Key terms:
  • Birdwatcher: Watches birds everywhere.
  • Twitcher: Travels long distances to "tick off" birds.

Why Study Birds?

• Valuable environmental indicators.
• Impact (+/-) plant and environmental health.
• Impact (+/-) farming systems.
• Birds are interesting in their own right.

How to Study Birds

1. Good set of ears
2. Good set of binoculars
3. Good bird identification book/app
4. Plenty of patience
5. Insect repellent, sun protection
6. Best to do it before you have children

Australian Birds

• Nearly 800 species.
• Many vagrants or rare visitors.
• Many species are rare or in decline.
• Found virtually everywhere.
• "May your bird-watching be auspicious!"

Bird Ecological Functions

• Likely the most important seed distributor.
• Pollination.
• Arthropod check.
• Landscape engineering.
• Nutrient redistribution as both predator, prey, and via excretion.

Chilli-Bird Relationship

• Chillis and birds have a long-established beneficial relationship.
• Birds disperse chilli seeds widely in exchange for the fruit.
• Capsaicin evolved to prevent consumption by unsuitable seed transporters.
• Humans have preserved chillis, creating an evolutionary paradox.

Dinosaur Origin

• Birds are direct descendants of dinosaurs.
• Archaeopteryx is the most famous example.
• First appeared in the Jurassic period.
• Theropod ancestors.
• Unlike dinosaurs, birds survived the K-T extinction event.

Bird Relatives and Survival

• Nearest bird relatives are crocodiles.
• Birds and several other groups survived the K/T extinction.
• Dinosaurs, ichthyosaurs, plesiosaurs, mosasaurs, and pterosaurs did not survive.

Ancient Radiations

• Birds diversified significantly after the dinosaur extinction.
• Flight vs. continental drift is a major driver of speciation.
• All birds had flying ancestors.
• Even emus and cassowaries have wings and flying ancestors.
• Several birds have lost flight, particularly in predator-poor environments like New Zealand.

Birds as Agricultural Pests

• Birds can eat or damage crops.
• Can exist in massive numbers.
• Increased water and food supplies exacerbate the issue.
• Control permits and non-permitted control methods exist.
• Netting and scarecrows are used for control.

Cockatoos as Pests

• Cockatoos are among the most significant pests.
• More water and seed are available than previously.
• Cockatoo numbers are greater now than before European settlement.
• Farmers are frustrated by limited control measures.

Birds as Agricultural Allies

• Birds can control insect pests of crops.
• Owls control rodents.
• Ducks have been used for snail control.
• Nutrient depositions (N, P).
• Parasite removal (e.g., cattle egret).
• Birds can be farmed (e.g., chickens, turkeys).

Phosphorous Fertilizers

• Many phosphorous fertilizers are of avian origin.
• Guano deposits on off-shore islands are mined.
• This was a huge industry in the 19th and 20th centuries.
• The industry is being renewed as part of the ‘organic’ movement.

Human Impacts on Birds

• Humans have had a significant impact on bird populations.

Passenger Pigeons

• The passenger pigeon was once incredibly abundant in the United States.
• They laid only one or two eggs and reared only one young one.
• Their abundance was due to a constant supply of wholesome food over a vast region.
• Their ability to fly long distances allowed them to find new food sources.
• This example highlights the importance of a constant food supply for the rapid increase of a species.

The Great Sparrow Campaign

• Mao's advisors calculated that individual sparrows eat ~4 kg of rice per year.
• Sparrows were persecuted as part of the Four Pests Campaign from 1958-1962.
• Sparrows also ate grasshoppers and other insects.
• Sparrows nearly went extinct.
• This resulted in the greatest famine in history.
• Sparrows were imported from the USSR to recover the population.

Greater Honeyguide

• The greater honeyguide ( Indicator indicator ) is an African bird that finds beehives.
• It then finds a human and vocalizes and leads the human to the hive.
• The human gets honey, and the bird gets bees.

Birds Benefiting from Humans

• Some birds have done well because of humans.
• Many species benefit from human impacts.
• Examples include noisy miners, magpies, cockatoos, currawongs, butcherbirds, and kookaburras.
• This can negatively impact other species through displacement, predation, and competition.

Bell Miner Decline

• Eucalypt forests are dying when bell miners move in.
• Bell miners are excluding pardalotes.
• Pardalotes eat lerps.
• Lerps are eating trees and possibly infecting them with Liberibacter.

Impact of Chemical Agriculture on Birds

• Chemical insecticide use led to cataclysmic declines in apex birds.
• Bioaccumulation of DDT & OCs occurred.
• Dichlorodiphenyltrichloroethane
• Persistent organic pollutants (POPs)
• POPs cannot be broken down or excreted.

Bioaccumulation

• Diagram illustrating how bioaccumulation works.
• Shows the accumulation of chemicals (CI) through the food chain.

Bioaccumulation in Apex Predators

• Bioaccumulation weakened eggshells.
• Nestling birds would crush shells as they warmed them.
• Ospreys were perilously close to extinction.
• DDT et al. were banned in the 1990s.
• Seabirds are recovering.

Plastic Waste

• Tonnages are astonishing.
• Major impacts on seabirds.

Conclusions

• Birds serve extensive ecological functions.
• Without birds, agroecosystems collapse.
• Birds can enrich our lives.
• If you love birds, you are never alone.