Nick Baker’s Hid­den Bri­tain

BBC Wildlife Magazine - - Contents - NICK BAKER Dis­cov­ers a duck with a sur­pris­ing tal­ent

The shov­eler duck’s sur­pris­ing tal­ent

The ducks, their poly­chro­matic heads sparkling in the low win­ter sun, spun around and around al­most on the spot. These north­ern shov­eler ducks were among the many other species of what are of­ten termed dab­bling duck.

There were wigeon, gad­wall, teal and the ubiq­ui­tous ‘duck pond duck’ the mal­lard. They each had their own sport: the teal worked around the edges of the reeds in the shal­lows, the gad­wall in the open, the mal­lard mid-wa­ter, of­ten up-ended, the wigeon leav­ing the wa­ter en­tirely and graz­ing the sur­round­ing short veg­e­ta­tion.

How­ever it was the mo­tion of the shov­el­ers that set them apart, and be­cause they were close to the hide in which I sat, it was the sound they made too – a bright, rhyth­mic but con­tin­u­ous splash­ing, like a fast drip­ping kitchen-sink tap.

What are they do­ing? Well it’s clear they’re feed­ing – but on what? And how? It’s part of the fas­ci­na­tion of bird­watch­ing – try­ing to spot the niches that dif­fer­ent birds ex­ploit. While the rafts of float­ing seeds of plant ma­te­rial, the sub­merged veg­e­ta­tion and grass grow­ing around the edges make some sense as a food source, the wa­ter that the shov­el­ers were ‘shov­el­ling’ seemed to be just that – wa­ter (slightly tur­bid, green/brown wa­ter, but wa­ter none­the­less). It seems that these spec­tac­u­lar look­ing birds were con­jur­ing up all their win­ter en­ergy from the murk.

Take a drop of this green murk and stick it un­der a mi­cro­scope at 30x mag­ni­fi­ca­tion, and it be­comes a nu­tri­tious soup – a seething, fizzing mass of lit­tle lives from tiny pro­to­zoa to rel­a­tive gi­ants in the form of the crea­tures eat­ing them: midge lar­vae, daph­nia and cy­clops, bee­tles and wa­ter boat­men – a good meal for those tooled up for the job. As you’ve prob­a­bly guessed, this duck’s suc­cess has some­thing to do with the in­cred­i­ble spat­u­late hard­ware stuck to the front of the bird: at around 7cm long, its bill is longer than the head it­self.

The shov­eler is a spe­cial­ist at soup strain­ing. While many of the other dab­bling ducks have a se­ries of comb-like ser­ra­tions called lamel­lae on the in­side edges (to­mia) of both up­per and lower mandibles, al­low­ing a de­gree of fil­ter­ing, the shov­eler takes this de­sign fea­ture to an­other level.

Com­pared with a mal­lard, a suc­cess­ful gen­er­al­ist, which has 50–70 of these short and stubby lamel­lae, the shov­eler has about 220 on its lower mandible and 180 on the up­per.

But it’s not just the num­ber of these combs that is spec­tac­u­lar; they are long, too – some ap­proach­ing a cen­time­tre. They are in ef­fect sim­i­lar to the baleen plates of a whale, and in some re­spects the feed­ing mech­a­nism isn’t dis­sim­i­lar ei­ther.

While these lamel­lae are hid­den from view most of the time, there is a sec­tion of the bill which looks like the up­turned cor­ner of a smile – ac­tu­ally called the grin gap – and in good light, you can just about make them out.

The up­per mandible fits over the lower one, and when the bill is half open the lamel­lae in the top and the bot­tom mesh to­gether form­ing a fil­ter cage. And this ex­tra­or­di­nary bill de­sign is only part of the story: when cou­pled with the avian world’s most bizarre tongue ( see left), it be­comes a highly ef­fec­tive fil­ter pump, too.

NICK BAKER is a nat­u­ral­ist, au­thor and TV pre­sen­ter.

Shov­el­ers move around and around, us­ing their uniquely de­signed bills to fil­ter food from the murky wa­ter.

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