My piece for Wiltshire Wildlife Trust, promoting their new project "bird's in our buildings" by looking at the incredible nesting habits of everybody's favourite House-related bird (3 guesses as to which bird I mean...).
House Sparrows. Since their entrance into the Fossil Record 100,000 years ago, betrayed by a fossilized jawbone unearthed in a human-inhabited Israeli cave, they’ve skyrocketed. Hitchhiking across oceans and continents with humans, they’ve conquered the world at our side. Today, there’re over a colossal 1.6 billion of them
Bar their love for humankind, their success is largely owed to two factors: their dietary flexibility, and nesting flexibility. With a biological toolkit from vice-like beaks, primed for seed-dissection, to powerful neck muscles for striking invertebrates, they’ve been observed eating everything from lizards to baby mice! Partner this with their ability to nonchalantly shove a nest virtually anywhere near humans, is it a surprise they’re everywhere? In fact, the only locations they veer away from nesting in, are “wild” ones like woodlands.
They’ve been recorded nesting from the dizzyingly high observation deck on the Empire State Building, to the the depths of Yorkshire Coalmines, 640m below ground. Everywhere from disused military tanks to the ever-bobbing heads of oil pumps, is on their real-estate market.
The nest itself is a contraption of twigs, paper, moss, string, and feathers (sometimes plucked from live Pigeons!) which can swell to the size of a football when free-standing.
Intriguing studies into their nests also revealed their ability to self-medicate. By threading sprigs of Fireweed into them, a plant with anti-Malarial properties, their nests become partially immune to the vicious “Avian Malaria”, a disease fatal to an undeveloped chick. Incredible, considering a Sparrow brain weighs less than a paperclip.
They’re also one of the few birds that can nest in every month of the year, though construction peaks during March, with a clutch of 1-9 marbled eggs placed in soon after. Once hatched, it’s only a mere 14 days until the intrepid chicks are flight-worthy, affectionately shown the ropes of life by their parents for a few weeks.
And for these brief few weeks in late Summer/early Autumn, coinciding with the harvest, neighbouring House Sparrow flocks conjoin. Bolstered by the inquisitive juveniles, tens of thousands can be seen. A “super-flock”, pleating and rolling similar to a Starling murmuration. Sadly, this spectacle is almost absent in modern Britain, as House Sparrows have declined in recent decades.
Deceivingly, they’ve scored #1 on the RSPB’s infamous Big Garden Birdwatch, 18 consecutive years as of 2021, crowning them our commonest Garden bird. However, since the survey’s advent in 1949, they’ve declined by 58%. Other high rankers like the Woodpigeon, however, having increased, the Woodpigeon doing so by an astounding 1029%.
Nationally, the picture worsens. Britain only has about 29% of the House Sparrows it did in 1977, with 21.7million lost between 1966-2016, a pace of almost one per minute.
Alongside pollution, and diminishing invertebrate food, lacking nesting spots has been deemed a primary culprit by the British Trust for Ornithology (BTO). The cracks and crevices in our buildings vital for nest sites lost to development.
That’s why projects like Birds in Buildings, studying the fascinating nesting habits of birds like House Sparrows, are crucial if we’re to have a future alongside our feathered tenants.
Seen a house sparrow nesting in a building near you?