Eurasian Tree Sparrow (Passer montanus) — once one of Taiwan's most common birds (Photo: Unsplash, free license)
1. The Harsh Numbers: How Many Sparrows Has Taiwan Lost?
Taiwan's sparrow is officially known as the Eurasian Tree Sparrow (Passer montanus), one of Taiwan's most common resident birds. But the label "most common" is being rewritten.
Taiwan Breeding Bird Survey (BBS) Data
3.5 million
2013 BBS estimated total sparrow population in Taiwan
-57%
2009-2020 sparrow population decline in northern Taiwan
-10%
Overall sparrow decline across Taiwan in the same period
+550%
2009-2020 growth of invasive Common Myna population
The Endemic Species Research Institute (ESRI) has conducted the Taiwan Breeding Bird Survey (BBS Taiwan) since 2009, Taiwan's largest-scale bird population monitoring program. The data clearly shows: sparrows are declining, especially in the north.
However, ESRI assistant researcher Lin Da-Li also notes that analyzing 2011-2019 BBS data with different statistical methods shows sparrow numbers have declined, but the decline does not reach statistical significance. This means "sparrows are declining" is real, but the exact rate of decline needs longer-term monitoring to confirm.
Scientific honesty matters: "Appears to have declined significantly" and "statistically significant decline" are two different things. But a species doesn't need to wait for statistical significance to deserve attention — by the day it becomes significant, it may already be too late.
2. Not Just Taiwan: Sparrows Are Disappearing Worldwide
Sparrows were once the most familiar birds in cities worldwide (Photo: Unsplash, free license)
| Region | Species | Decline | Time Period |
|---|---|---|---|
| United Kingdom | House Sparrow | -68% (up to -90% in some areas) | 1970s to present |
| Europe overall | House Sparrow | -60% | 1980s to present |
| Paris | House Sparrow | -89% | 2003-2017 |
| Indian cities | House Sparrow | Over -70% | Past 20 years |
| North America | House Sparrow | Reporting rate -7.5%, flock size -22% | 1995-2016 |
| Europe | Tree Sparrow | -94% | 1970 to present |
| Northern Taiwan | Tree Sparrow | -57% | 2009-2020 |
| Hong Kong | Tree Sparrow | Significant decline | Confirmed in 2021 census |
From London to Taipei, from Paris to Mumbai, sparrows are declining everywhere. This is not a single country's problem but the shared consequence of global urbanization and agricultural industrialization.
3. First Principles Analysis: Why Are Sparrows Disappearing?
Sparrow decline isn't caused by a single factor but by at least five forces acting simultaneously.
Cause 1: Pesticides (Especially Neonicotinoid Insecticides)
Neonicotinoid insecticides are currently the world's most widely used insecticides and one of the most scientifically scrutinized factors in sparrow decline.
Molenaar et al. (2024) published a meta-analysis in Ecology Letters showing that neonicotinoids negatively impact every aspect of bird life: from reproduction and body weight to survival rates.
Specific damage mechanisms:
1. Direct poisoning: A migratory bird that eats just 1-2 neonicotinoid-coated seeds will immediately lose weight and be forced to delay migration.
2. Food chain collapse: These insecticides kill field insects, and sparrow chicks are 100% dependent on insects for food. Adults eat seeds, but nestlings need protein-rich insects to grow. No insects, starving chicks.
3. Chronic accumulation: Research found that all sampled sparrow feathers contained at least one neonicotinoid compound, with significantly higher concentrations on conventional farms than organic farms.
"Because these modern insecticides are highly effective at suppressing local insect populations, insectivorous birds are negatively affected by the pesticide-induced reduction in food supply."
— Molenaar et al., 2024, Ecology Letters
Cause 2: Habitat Loss
- Traditional rural houses demolished and rebuilt
- Vacant lots and grasslands turned into parking lots
- Rice paddies converted to factories or housing
- Lowland afforestation actually reduces sparrow habitat (sparrows don't live in forests)
- Old buildings with crevices (for nesting)
- Open farmland and grassland (for foraging)
- Shrubs and low trees (for shelter)
- Stable insect and seed food sources
Modern buildings use sealed glass, steel, and concrete, leaving no small holes or crevices. Old houses had gaps under the eaves — sparrows' favorite nesting spots. New buildings are completely sealed, leaving sparrows nowhere to live.
Cause 3: Invasive Species (A Problem Unique to Taiwan)
Sparrows need cavities for nesting, but modern buildings no longer have crevices (Photo: Unsplash, free license)
This is a unique threat facing Taiwan's sparrows. Four or five decades ago, the pet trade imported White-vented Mynas and Common Mynas from Southeast Asia (popular because they can mimic human speech). When the bird-keeping craze faded, large numbers of mynas were abandoned or escaped.
+550%
2009-2020 Common Myna population growth
+250%
2009-2020 White-vented Myna population growth
62%
White-vented Myna share of total myna population in Taiwan
5%
Remaining share of native Taiwan Crested Myna
White-vented Mynas compete with sparrows for the same resource — cavity nest sites. Researcher Hsu Fu-Hsiung's team surveyed 400 metal pipes in Chiayi and found a quarter were occupied by White-vented Mynas for nesting. Even worse, White-vented Mynas prey on sparrow chicks. Mother sparrows can only cry helplessly by the nest, powerless to stop them.
Cause 4: Urbanization and Electromagnetic Radiation
Everaert & Bauwens (2007) published a study in an academic journal finding that in Belgium, areas with higher electromagnetic field strength had significantly lower sparrow densities. Observed phenomena included nest abandonment, feather degradation, behavioral abnormalities, and reduced survival rates.
However, this study is highly controversial. Subsequent scholars pointed out this could be correlation rather than causation — areas with more cell towers typically have newer, more sealed buildings that are inherently unsuitable for sparrow nesting. The scientific community currently has no consensus on whether electromagnetic radiation directly affects sparrow populations.
Cause 5: Climate Change and Ecological Chain Reactions
Taiwan's Russet Sparrow population has dropped to fewer than a thousand. A Greenpeace investigation found that the sharp decline in millet field area in Pingtung is highly correlated with the rapid decline of Russet Sparrow populations. Climate change affects crop planting patterns, which in turn affects birds dependent on those crops.
4. Causal Relationship Overview
| Threat Factor | Mechanism | Evidence Strength | Taiwan Specifics |
|---|---|---|---|
| Neonicotinoid pesticides | Kill insects → chicks starve → breeding failure | Strong (multiple meta-analyses) | Taiwan has high pesticide usage |
| Habitat loss | Old buildings demolished → no nesting sites | Strong (globally consistent) | Rapid farmland conversion |
| Invasive species competition | Compete for nest cavities + prey on chicks | Moderate-strong (Taiwan field surveys) | Uniquely severe in Taiwan |
| Electromagnetic radiation | May interfere with breeding behavior | Weak (highly controversial) | No Taiwan-specific studies |
| Climate change | Alters crops → food source changes | Moderate (indirect evidence) | More obvious for Russet Sparrow |
Core conclusion: Sparrow decline isn't caused by a single factor but by a triple blow of "pesticides x habitat loss x invasive species." Like a person simultaneously losing their job, home, and sense of safety — any one of these alone is survivable, but all three together lead to collapse.
5. Historical Parallels
In 1958, Mao Zedong launched the "Four Pests" campaign, listing sparrows as one of the four pests (alongside flies, mosquitoes, and rats). The rationale was that sparrows ate grain, damaging agriculture.
The entire nation was mobilized to kill sparrows: beating drums and gongs to prevent sparrows from resting until they dropped dead from exhaustion. An estimated one billion sparrows were killed in just one year.
Result: After sparrows disappeared, locusts lost their natural predator and multiplied massively, devastating crops. This became a major contributing factor to the Great Famine of 1959-1961, causing tens of millions of deaths.
Mao eventually removed sparrows from the Four Pests list in 1960, replacing them with bedbugs. But it was too late.
Lesson: Sparrows are not "pest birds" but an indispensable link in the ecological chain. The insects they eat are far more valuable than the grain they consume. The chain reactions of eliminating a species often exceed humanity's predictive capacity.
Zhuge Liang's governance of Shu relied not only on elite troops for battles but emphasized local garrisons and military farming units. These "unremarkable standing forces" maintained Shu Han's daily operations — patrols, public order, farming, and logistics.
Sparrows are the "standing army" of the ecosystem. Every day they consume massive amounts of pest insects and weed seeds, maintaining basic order in farmland. You won't notice their contribution until they disappear. Just as Shu Han rapidly collapsed after Zhuge Liang's death — not because they lost a genius, but because the force that sustained daily operations was severed.
The rows of sparrows once perched on power lines are becoming increasingly rare (Photo: Unsplash, free license)
6. Business Insights
Sparrows were so common that nobody cared about their decline. By the time people noticed, half were already gone.
Business lesson: The most easily overlooked people in a company are those who have "always been there" — veteran customer service reps, backend operations staff, administrative assistants. They are your company's sparrows: you never think they're important until they leave, and then you discover the entire system starts breaking down. Don't wait for "sparrows to disappear" before recognizing their value.
White-vented Mynas aren't smarter than sparrows and don't fly faster, but they compete for the same type of nesting cavity. The key to competition isn't "who's better" but "who's grabbing the same scarce resource."
Business lesson: The most dangerous competitor isn't the company that does things better than you, but the one that's targeting the same customers. Uber Eats' biggest threat to restaurants isn't "faster delivery" but "stealing the direct relationship between restaurants and customers." Watch who's stealing your "nesting sites."
Pesticides don't kill sparrows — they kill insects. But insects die → chicks starve → breeding fails → population collapses. The truly lethal blow isn't the first hit but the third and fourth chain reactions.
Business lesson: When you cut a "unimportant" department or function, think three layers deep: What does this change affect? What does that effect affect in turn? The Great Famine wasn't caused by "killing sparrows" but by "killing sparrows → locust explosion → food supply collapse." Before cutting budgets, draw a chain reaction diagram first.
References
- Taiwan Breeding Bird Survey (BBS Taiwan). Official Website
- Lin, D.L. et al. (2022). Taiwan's Breeding Bird Survey reveals very few declining species. Ecological Indicators.
- Molenaar, F.M. et al. (2024). Neonicotinoids Impact All Aspects of Bird Life: A Meta-Analysis. Ecology Letters.
- Everaert, J. & Bauwens, D. (2007). The urban decline of the house sparrow: a possible link with electromagnetic radiation. Electromagnetic Biology and Medicine.
- De Laet, J. & Summers-Smith, J.D. (2007). The decline of the House Sparrow: A review.
- Rosenberg, K.V. et al. (2019). Decline of the North American avifauna. Science. — Cornell University coverage
- Solomon, N.G. et al. (2025). Influence of Food Distribution and Relatedness on Social Interactions in a Colony of Free-Ranging Domestic Cats. Ethology.
- Greenpeace. Vanishing millet fields, endangered sparrows: The climate crisis and Taiwan's forgotten guardians.
- Newsmarket (2023). Are sparrows really declining? "Pest birds" are actually a misunderstanding?
- PTS News (2020). Sparrow numbers declining year by year — Taiwan's ecology flashing warning signs.
- PTS Our Island. How many mynas? Native vs. invasive species habitat competition.
- PTS News (2022). Invasive myna species surge 550% in 12 years.
- CNA (2018). Sparrow numbers declining year after year — experts' analysis raises concerns.
- Hong Kong Bird Watching Society (2021). Hong Kong Sparrow Census 2021.
- Photos: Unsplash (free license)