I’ve always been fascinated by the old-fashioned and regional names given to birds, of which the gadwall has many, including “grey duck”, “rodge” and “sand widgeon”. But when I discovered they were once known as “bastards” on the south-east coast of England, I was intrigued. Hearing of pesky crows and magpies being referred to as such isn’t rare, but how could one of my favouritespecies of duck have earned such a degenerate name?

According to James B. Ellman, who contributed to The Zoologist — a popular miscellany of natural history, founded in 1843 and amalgamated with British Birds in 1916 — it was because wildfowlers of the day considered gadwall a hybrid between mallard and widgeon. Given the scarcity of gadwall in England at the time, a shortage of bird identification books, and the duck’s being between mallard and widgeon size, forgiving those old gunners this derogatory name isn’t difficult. In the literary classic Shooting: Moor and Marsh, published in 1889, even the esteemed sportsmen Lord Walsingham and Sir Ralph Payne – Gallwey admit to having occasionally spared gadwall, because they could not tell if they were tame or wild birds.

There’s no doubt that gadwall catch people out. Over the years, I’ve witnessed many experienced game Shots struggling to identify a gadwall when they have been added to the bag. I suspect there’s no more frequently misidentified British quarry species, particularly the female gadwall. Traditionally, the winter distribution of gadwall in Britain has been patchy compared with more commonly shot duck species.

Consequently, opportunities to shoot gadwall have been few and far between, hence the scope for uncertainty.

Like a mallard but smaller

Perhaps a description is in order. Look closely at a drake in full winter plumage and he’s a sight to behold. I shot my first male gadwall in 1994, during morning flight on a marsh in the south of Oregon, and I’ve been charmed by them ever since.

He’s slightly smaller than a mallard, with a narrower, squarer head. He has a shorter neck, almost black bill and the most exquisite, dark scalloped and pale crescent pencil-markings on grey-toned feathers about his nape, chest and flanks. He sports a full black stern, with rich chestnut wing coverts, which, sadly, are rarely displayed while he’s at rest. However, most of the time, his striking white speculum feathers are on show, which serve as a reliable field mark, for no other British duck species has rectangular white wing patches — others tend to have colourful, iridescent blue or green ones.

His mate resembles a small, female mallard, with greyer plumage. Distinguishing features include bright orange sides to her bill, white speculum feathers and, like her mate, a pale cream undercarriage — another useful field sign, especially if the duck pass overhead.

So, if you shoot an early-season duck that broadly resembles a young, female mallard but also fits the description above, a toast might be in order — you’ve probably bagged your first “gaddy”! If so, be sure to don your cooking apron, and pop the cork on a good bottle of Burgundy, for as a freshwater-feeding, herbivorous duck, a roasted gadwall makes for extremely good eating.

I’ve always found gadwall to be a shy and discreet duck, yet its scientific name, Anas strepera, comes from the Latin strepo, meaning “I make a noise”. The drake’s repertoire of calls includes a nasal “ahrrk”, which resembles the guttural tone of a corncrake’s call, and a soft whistle. The duck is much louder, and her quacking is reminiscent of a mallard, though higher-pitched and more strongly diminuendo — a sort of “kaaak-kaaak-kak-kak-kak”.

Slow to colonise Britain

Though gadwall have long visited Britain, their historic stronghold is East Anglia, where they were highly prized by the old fen men. Interestingly, there are no records of gadwall having bred in Britain until 1850, after a single pair was caught the previous winter on the South Acre duck decoy at Dersingham in Norfolk, pinioned and released on nearby Narford Lake. This pair bred and attracted winter migrants, which stayed to nest. The local population expanded, gadwall began to colonise Breckland, and in 1916 they were first recorded breeding on the Norfolk Broads.

From 1950 onwards, pockets of gadwall established elsewhere. This was the result of birds escaping from private waterfowl collections and from hand-reared birds released by wildfowlers in a program co-ordinated by the then Wildfowlers Association of Great Britain and Ireland (WAGBI). From 1965 to 1972, WAGBI released hand-reared gadwall at its experimental wildfowl reserve near Sevenoaks, in Kent, every year. Further notable releases took place in Leicestershire and Cumbria.

Though WAGBI’s release efforts were aimed at augmenting the breeding population, it became apparent that provision and management of good wetland habitats for both breeding and over-wintering wildfowl was the real answer, not releasing captive-bred birds. Since then, wildfowling clubs have been instrumental in managing habitats that resident and migratory gadwall thrive in. Gadwall have now colonised freshwater and brackish wetlands across the UK, but localities with large reservoirs and flooded gravel pits “restored” for wildlife are hotspots.

Current estimates by the British Trust for Ornithology (BTO) suggest a summer breeding population of around 1,700 pairs, with numbers rising. This upward trend is mirrored elsewhere: there have been major expansions in the gadwall’s breeding range in both Continental Europe and North America.

Ringing recoveries suggest that about 25 per cent of England’s breeding gadwall move to the Low Countries, France and Spain in winter, and that up to 50 per cent of English wintering gadwall come from Eastern Europe. Our winter population has increased spectacularly — a whopping 50-fold increase since the 1960s. The BTO’s current estimate is of around 25,000 over-wintering birds, most of them in England. Gadwall numbers are rising similarly throughout north-west Europe — around nine per cent per annum since the 1960s.

According to wildfowl bag returns published by the Crown Estate, from 2004-2008 the average number of gadwall shot on the Crown foreshore each season was 37 birds. From 2008-2012, that figure increased threefold, to 106.

As a mainly inland duck species, we might expect relatively more gadwall to be accounted for on shoot-day duck drives, or as they tumble into flightponds at dusk. But the Game and Wildlife Conservation Trust’s National Gamebag Census, which records bag data from shooting estates, has too few records of gadwall to detect a trend in bag numbers. Perhaps that situation will change if gadwall become more widely distributed.

Reasons for the boom

So why are gadwall doing so well? In the UK, for both our summer and winter population, it seems likely that new, man-made wetland habitat is the answer, but the gadwall’s propensity for piracy might also be key. As a dabbling duck, gadwall feed mainly on emergent and submergent vegetation which they gather by surface-feeding and “up-ending” to strip greenery from shallow water. Such plant material is nutrient poor, and birds must eat vast amounts of it for sustenance.

This necessitates long periods of non-disturbance while feeding, or shallow, eutrophic waters where plant biomass is high. However, a number of scientific studies show that gadwall increasingly steal vegetation gathered by coots, which can dive for plant material.

This thieving behaviour not only saves the gadwall energy, it enables the birds to exploit reservoirs and flooded gravel pits, which would otherwise be too deep for them to feed in. Food thieving from coots is a classic example of kleptoparasitism — a behaviour more commonly associated with large gulls and skuas, which are notorious for chasing and harassing smaller, diving seabirds until they relinquish their meals of fish.

If recent population trends continue, the next generation of sportsmen and women are in for a treat, for gadwall are extremely sporting birds, stunning to look at and delicious to eat. At a time when the winter population of the mallard shows signs of a decline, it’s heartening that at least one duck quarry species is thriving. Let’s enjoy gadwall, and learn how to recognise them, but please, as much as I love colloquial bird names, let’s not link their habit of “thieving” with their old name, “bastard”!

For details on how to contribute to the National Gamebag Census, contact Gillian Gooderham, tel 01425 651019, or email ggooderham@gwct.org.uk.