What’s the UK’s most common breeding bird?

It’s a classic pub quiz question: “What’s the UK’s most common breeding bird?”. Many people might think of Woodpigeon or House Sparrow, Starling, perhaps, because we see so many in our gardens. Indeed, House Sparrow is the most common bird in our gardens, but that doesn’t take into account the millions of birds in the countryside (ignoring chickens which aren’t wild birds). The answer to the question is in fact the Wren (Troglodytes troglodytes). There are about 8,600,000 breeding pairs of Wren in the UK compared with just 5,300,000 pairs of House Sparrow.

Bizarrely, when I posted this fact on Facebook with the above photo of a Wren at RSPB Titchwell, one friend asked, quite innocently, which is the most abundant UK breeding bird by weight? I assumed he meant mass and so I looked up the numbers and the average mass of a few species and did some calculations, I may well have overlooked a bird that comes in heavier, but here’s my Top Ten UK breeding birds not by number but by national tonnage:

Woodpigeon 457 g – 5.4 million pairs –> 4940 tonnes
Blackbird 100 g – 7m pairs –> 1400 tonnes
Collared Dove 181 g – 990,000 pairs –> 360 tonnes
Greylag Goose 3.6 kg – 46000 pairs –> 331 tonnes
Starling 75 g – 1.8 million pairs –> 270 tonnes
House Sparrow 32 g – 5.3m pairs –> 169 tonnes
Wren 9 g – 8.6 million pairs –> 160 tonnes
Chaffinch 25 g – 6.2m pairs –> 155 tonnes
Mute Swan 10 kg – 6400 pairs –> 128 tonnes
Robin 19 g – 6.7 million pairs –> 127 tonnes

Just outside the top ten, we have:
Song Thrush 80 g – 1.2 million pairs –> 96 tonnes
Dunnock 20 g – 2.3 million pairs –> 46 tonnes
Blue Tit 11 g – 3.6 million pairs –> 39.6 tonnes