House Sparrows: the perfect predators
Typically, House Sparrows are(unfairly!) brushed off with the notion of being boring, brown little things, gingerly sticking to people’s birdfeeders.
Only this is outrageously un-true! One of my trump facts (regularly making an appearance on my Twitter profile to the point of annoyance) is how “only 30% of a male House Sparrow is actually brown” and alongside it, often a mention of their incredibly surprising diet. Let’s just say they aren’t the strict granivores/seedeaters they’re stereotyped...
Well, admittedly, a large portion of their diet today is various seeds, grains, and cereals, but this is partly because there’s not much else in our anthropogenic world. Similar to how Peregrine Falcons are now ‘categorized’ as clifftop/building-side nesters. However, as famously displayed in Knepp Estate (a famous rewilding project) they comfortably nest in trees, just requiring a certain, niche type.
And I believe that, with invertebrates dying out the rate they are (one of the top 3 reasons behind Sparrow decline according to the RSPB) House Sparrows have had to resort to a less nutritional, seed-based diet, or doomed to follow fortunes of birds like the Turtle Dove (which unbeknownst to most, eats beetles, molluscs and other invertebrates given the chance, and is likely going to be extinct within the decade).
Indeed, House Sparrows chicks aren’t even able to digest the armoured seeds/cereals the adults do and must be fed an exclusively invertebrate diet (hence why their breeding season is timed to perfection with peak invertebrate season). Adults forage for a range of invertebrates (for them and their young) from beetles, flies, moth/butterfly caterpillars, snails, and aphids (a favourite! … for the sparrows not me). In coastal regions they also hunt minute crustaceans like the armoured Sandhoppers in amongst the seaweed (something I’ve been eagerly trying to see for months).
And they have a multitude of different tactics in their arsenal to catch their prey with too, all uniquely perfected. They’ll stalk worms through the leaflitter, harvest aphids and Cabbage White caterpillars from the underside of Crucifers (a tip for gardeners there-encourage House Sparrows for free pest-control!) probe lumps of rotting wood for beetle grubs, pounce on unsuspecting moths or bees, and even catch flying insects in mid-air feats of acrobatics.
As they mature, discarding their scruffy juvenile plumage to don their immaculate chestnut and grey suits, they veer away from eating invertebrates and move to a more seed/grain-based diet. And while their beaks appear ideal for dissecting and devouring tough cereals and grains, to quote the RSPB themselves when talking about their preference for cereals etc over natural seeds/foodstuffs “While the nutritional value of these seeds is relatively low compared with larger, oilier seeds, they’re often exceptionally abundant, and thus represent the most efficient feeding option” (2019 RSPB Spotlight Sparrows, Jane-Beer Amy. pg.51). Reinforcing that their lifestyles/diets have been bent out of shape overtime by evolution to fit the circumstances.
However, adults are still very partial to the odd invertebrate, and alongside the usual harvesting of aphids from nettles, or probing for worms, accomplished individuals have mastered how to rob Spiders webs of trapped flies, and twist at breakneck speed to rob other birds like Blue Tits of their prey. When you take the time to watch them, House Sparrows really do match the grace and elegance of any of the more exciting birds like Hobbies and Flycatchers we’re usually so focused on spotting.
Alongside this, adults House Sparrows have been known to tackle much larger prey items when food is running low, known to tackle things as big as Mice and Wall Lizards. And in parts of Italy, Geckos can make up a substantial portion of the overall food they eat, hard to imagine, watching them gingerly thrusting their faces into piles of birdseed or a fat ball.
This is because overall, House Sparrows are actually very lazy feeders (don’t tell them I said that though) and only display these amazing feats of hunting and aerobatics when desperate for food. Today, pre-made and delivered bird-food makes up a fat slice of our urban House Sparrows’ diets.
Recently the breeding season for House Sparrows, albeit always long, has been thrown out the window. Thanks to a cocktail of warming Winters, heat from their urban city homes and mealworms, they’re one of the few birds that now raise young in every month of the year (although sadly this hasn’t yet helped stabilize their decline).
This is because, as mentioned, House Sparrow chicks aren’t able to digest the hardy seeds and cereals the adults do, so must be fed strictly invertebrates while developing. This previously acted as a cage, preventing them successfully breeding during Winter/Autumn, when invertebrates are either dormant or have died off for the year.
However, warmer Winters, keeping it just a degree or two milder, enabling invertebrates to stay on the wing, and people filling their gardens with mealworms for the birds (ideal surrogates for wild invertebrates) has meant there’s been a glut of Winter/Autumnal food, enabling House Sparrows to make the incredible jump to breeding in every month of the year!
The topic of House Sparrows and their diets is so fascinating, especially as most people see them and think “brown bird I see all the time that eats seeds then flies off” when in reality, they’re some of the smartest little predators out there. In the next blog, I’ll talk more about the incredible strategies behind how they catch their food, from raiding wasps and evolving to figure out how to break into milk bottles!
Peregrines nesting in Pine Trees: Tree, I. (2018). Wilding (1st ed., p. 273). [London]: Picador.
House Sparrow diets + eating large vertebrates: Beer, A. (2019). RSPB Spotlight Sparrows (1st ed., pp. 50-58). London: Bloomsbury Publishing Plc.
Top reasons for House Sparrow decline: Ornithology, B. (2021). House Sparrow Research. Retrieved 2 December 2021, from https://www.bto.org/our-science/projects/gbw/about/background/projects/sparrows