1 April 2021
Yes, today is April Fool’s Day but it’s no joke that house sparrows are in trouble. Though still considered pests in North America their population has declined dramatically, even in their native range. Seven years ago their disappearance was a mystery. Has anything changed?
Native to Eurasia and northern Africa, humans introduced house sparrows (Passer domesticus) to continents and islands worldwide in the 1800s, making them the most widely distributed wild bird on Earth. (Green is native range, yellow is introduced in the map below.)
House sparrows were successful worldwide — too successful — but as recently as 30 years ago they began a steady decline. They are down 84% now in North America and 60% in Europe. In the UK they are red-listed as a species of high conservation concern.
There have been many studies but no one cause for decline. The reasons include:
- Agricultural intensification (2002): lack of spilled grain and gleanings, livestock not raised outdoors, changed sowing and harvest schedules.
- Poor diet plus air pollution in cities (2017)
- Global insect decline (2019). However supplemental feeding in the UK doesn’t increase the overall population.
- Hawks are a problem in the UK but not in the US (2021)
The one thing we do know since 2014 is that there is no lack of nest sites.
In North America house sparrows are not just in trouble, they are trouble because of their aggression toward native species while nesting.
We’ll be happy to see them go but their mysterious decline should make us think. If a bird as hardy and human-oriented as the house sparrow is declining, it bodes ill for us too.
For more information read :
- My vintage blog post in 2014: Mysterious Disappearance
- Matthew Miller’s Nature.org article, 2019: Where have all the house sparrows gone?
- Cornell Lab, Feb 2021: Study finds even the common house sparrow is declining.