Big data study finds more than 50 billion birds in the world
University of New South Wales
The study --
which bases its findings on citizen science observations and detailed
algorithms -- estimates how many birds belong to 9700 different bird species,
including flightless birds like emus and penguins.
It found many
iconic Australian birds are numbered in the millions, like the Rainbow Lorikeet
(19 million), Sulphur-crested Cockatoo (10 million) and Laughing Kookaburra
(3.4 million). But other natives, like the rare Black-breasted Buttonquail,
only have around 100 members left.
The findings are
being published this week in the Proceedings of the National Academy of Sciences.
"Humans have spent a great deal of effort counting the members of our own species -- all 7.8 billion of us," says Associate Professor Will Cornwell, an ecologist at UNSW Science and co-senior author of the study.
"This is
the first comprehensive effort to count a suite of other species."
The research
team reached their figures by pooling together almost a billion bird sightings
logged on eBird, an online database of bird observations from citizen
scientists. Using this data -- and detailed case studies where available --
they then developed an algorithm to estimate the actual global population of
each bird species.
This calculation
took into account each species' 'detectability' -- that is, how likely it is
that a person will have spotted this bird and submitted the sighting to eBird.
Detectability can include factors like their size, colour, whether they fly in
flocks, and if they live close to cities.
"While this
study focuses on birds, our large-scale data integration approach could act as
a blueprint for calculating species-specific abundances for other groups of
animals," says study lead author Dr Corey Callaghan, who completed the
research while he was a postdoctoral researcher at UNSW Science.
"Quantifying
the abundance of a species is a crucial first step in conservation. By properly
counting what's out there, we learn what species might be vulnerable and can
track how these patterns change over time -- in other words, we can better
understand our baselines."
The study
dataset includes records for almost all (92 per cent) bird species currently
alive. However, the researchers say it's unlikely the remaining 8 per cent --
which were excluded for being so rare that we lacked available data -- would
have much impact on the overall estimate.
"It was
surprising that only a few species dominate the total number of individual
birds in the world," says Dr Callaghan, who is now based at the German
Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.
"What is it
about those species, evolutionarily, that has made them so
hyper-successful?"
But while some
bird populations are thriving, many others look a lot slimmer: around 12 per
cent of bird species included in the study have an estimated global population
of less than 5000. These include species such as the Chinese Crested Tern,
Noisy Scrub-bird, and Invisible Rail.
"We'll be
able to tell how these species are faring by repeating the study in five or 10
years," says A/Prof. Cornwell.
"If their
population numbers are going down, it could be a real alarm bell for the health
of our ecosystem."
A global effort
The study was
made possible with the help of more than 600,000 citizen scientists who
contributed their sightings to the eBird dataset between 2010 and 2019.
The Cornell Lab
of Ornithology, who run the eBird site, have made the data freely available.
"Large
global citizen science databases such as eBird are revolutionising our ability
to study macroecology," says A/Prof. Cornwell.
"This type
of data simply wasn't available a decade ago."
While the
research team are confident in their estimates, they acknowledge a degree of
uncertainty is inevitable when working with large datasets like this.
For example,
people who document the sightings may be more likely to seek out rare species,
or a species may be so rare that there simply isn't enough data.
"A range of
uncertainty is necessary when making global-level estimates," says
Professor Shinichi Nakagawa, an ecologist and statistician at UNSW Science and
co-senior author of the paper.
"Our
findings, while rough in some areas, represent the best-available data we
currently have for many species."
New data is
continuously added to eBird from both past records and present-day sightings.
The research team plan to repeat their analysis as more data becomes available.
"We will
need to repeat and refine this effort to really keep tabs on biodiversity --
especially as human-caused changes to the world continue and intensify,"
says Dr Callaghan.
A timeless hobby
Birdwatching --
or 'birding' for more serious enthusiasts -- is a popular hobby that dates back
to the late 18th century. The growing popularity of citizen scientist apps and
websites have made birdwatching an accessible way to engage with science.
"Birding is
a hobby that just keeps on giving," says Dr Callaghan.
"You can
usually find a bird or two to identify and watch anywhere you go, anytime of
the day, anywhere in the world."
People
interested in being involved with the project can create a birdwatching account
on eBird -- and A/Prof. Cornwell says that you don't need to be a bird expert
to get started.
"A great
starting point is to learn a handful of birds that come to your local area,
like Rainbow Lorikeets, Sulphur Crested Cockatoo, and Australian White
Ibis," he says.
"It can be
as simple as seeing if you can spot any out the window while you're drinking
your coffee in the morning."