36 Bird Dog Breeds: Pointers, Setters, Spaniels, and Retrievers Explained
October 23, 2026
Hunters in the field rely on a dog’s nose long before they ever raise a shotgun, and the right bird dog breeds can mean the difference between a slow afternoon and a full game bag. From English moors to Louisiana marshes, these working dogs were shaped over centuries to find, point, flush, or retrieve feathered game with remarkable precision.
This guide walks through 36 recognized bird dog breeds, organized loosely by function: pointers that freeze on scent, setters that crouch low before game, versatile European all-rounders, spaniels that flush birds at close range, and retrievers built to swim after fallen waterfowl. Whether the goal is a weekend hunting partner or a high-energy family companion, each entry below covers origin, working style, and temperament.
Pro Tip: Match a bird dog’s energy level to the actual hunting style practiced most often. A dog bred for all-day upland grouse hunts will struggle to settle into a household that only walks it around the block.
Before getting into individual breeds, it helps to understand how the American Kennel Club organizes its Sporting Group. Breeds in the Sporting Group were bred to assist hunters in the capture and retrieval of feathered game, with retrievers built for swimming and specializing in waterfowl while setters, spaniels, and pointing breeds work grasslands where quail, pheasant, and other game birds nest. The table below breaks down the four core functional families referenced throughout this guide.
| Functional Group | Primary Job | Typical Coat | Example Breeds |
|---|---|---|---|
| Pointers | Freeze and point at located game | Short or wirehaired | English Pointer, German Shorthaired Pointer, Vizsla |
| Setters | Crouch, then point toward scented birds | Long, feathered | English Setter, Irish Setter, Gordon Setter |
| Spaniels | Quarter close and flush birds within range | Wavy or curly, medium length | English Springer Spaniel, Boykin Spaniel, Field Spaniel |
| Retrievers | Swim after and carry back downed birds | Water-repellent double coat | Labrador Retriever, Golden Retriever, Chesapeake Bay Retriever |
1. English Pointer
Often simply called the Pointer, this breed is the namesake for an entire category of hunting dogs. All domestic dogs, including the Pointer, share the same classification, Canis lupus familiaris, yet centuries of selective breeding for scent work and stamina produced a dog built purely for finding upland birds at distance. The breed has an intense and natural affinity for finding, pointing, and retrieving game birds, and loves its family while getting along well with other dogs when not in the field.
Lean and muscular, the English Pointer covers huge amounts of ground in a day, which makes it better suited to open country hunting than small suburban yards. Its short coat sheds year-round but requires little grooming maintenance.
2. German Shorthaired Pointer
The German Shorthaired Pointer is a versatile hunter and all-purpose gun dog developed in the late 1800s to be suited for multiple tasks like pointing, retrieving, trailing game, and hunting small and large game. Known affectionately as the GSP, this breed ranks among the most popular hunting dogs in the United States today.
Recognized by the AKC in 1930, shorthairs originated in Germany as a combination of pointing bird dogs and hounds, and they remain an all-around bird dog adept at pointing and even retrieving everything from quail to pheasant. GSPs are also known for being friendly, smart, and willing to please, though they need exercise to satisfy their high activity level and sporting dog roots.
3. German Wirehaired Pointer
A closer look reveals why hunters in rough cover favor this breed over its shorthaired cousin: a dense, wiry coat protects the dog from thorns, cold water, and biting insects. The AKC recognized the German Wirehaired Pointer in 1959, decades after the German Shorthaired Pointer gained recognition in 1930.
The German Wirehaired Pointer carries a bristly beard and eyebrows that give it a distinctly weathered look. Owners who prefer low-shedding dog breeds often gravitate toward wirehaired pointers, since the coarse outer coat sheds less than smooth-coated hunting dogs.
Key Insight: Many European pointing breeds carry the designation HPR, short for Hunt, Point, and Retrieve. These versatile dogs were bred for farmers who needed one dog capable of handling fur, feather, and water work rather than specialists for each task.
4. German Longhaired Pointer
Less common in North America than its shorthaired and wirehaired relatives, the German Longhaired Pointer carries a flowing, setter-like coat with feathering on the ears, legs, and tail. The breed developed in Germany from a mix of spaniel-type hunting dogs and pointer bloodlines, giving it a gentler, more deliberate working style afield.
This pointer handles both upland birds and waterfowl competently, though its longer coat demands more brushing than its shorthaired cousins. Temperament tends toward calm and biddable, making it a reasonable choice for hunters who also want a mellow house dog.
5. Brittany
The Brittany is named for the French province in which it originated, and this versatile breed was developed in the early 20th century to create a superior pointing dog. Formerly known as Brittany Spaniels when first acknowledged by the AKC in 1934, they were renamed in 1983 after proving they could point birds at least as well as they could flush them.
Compact and energetic, the Brittany is often praised as an ideal apartment-to-field compromise breed: small enough for a smaller home, yet driven enough to hunt hard all day. Its orange-and-white or liver-and-white coat needs only occasional brushing.
6. Vizsla
The Vizsla traces its roots to Hungary, where falconers and mounted hunters once used an ancestor of this breed to track game across the Hungarian plains. The modern Vizsla carries a short, rust-golden coat that blends into tall grass, a trait that likely helped it slip close to wary birds.
Affectionate to the point of clinginess, Vizslas bond tightly with their handlers and generally dislike being left alone for long stretches. In the field they point with a high head and tail carried level, covering ground with an efficient, loping gait rather than the bounding run seen in some other pointing breeds.
7. Wirehaired Vizsla
Developed in the 1930s by Hungarian breeders who crossed the smooth Vizsla with German Wirehaired Pointer bloodlines, the Wirehaired Vizsla brings a thicker, weatherproof coat to the same golden-rust coloring. The result is a pointer better equipped for cold water retrieves and dense cover than its smooth-coated relative.
Despite the coat difference, this breed shares the Vizsla’s famously affectionate, people-oriented temperament. It remains a rarer sight in American fields than the standard Vizsla, though its numbers have grown steadily among hunters who want wirehair durability with Vizsla sensitivity.
8. Weimaraner
German aristocracy developed the Weimaraner in the early 1800s in the city of Weimar as an all-purpose hunting dog, a cross between Bloodhounds and German and French hunting dogs. Its striking silver-gray coat and pale eyes earned it the nickname “gray ghost” among American hunters and breed fans alike.
Important Note: Weimaraners were bred to hunt large game like boar and deer before shifting toward bird work, and that history shows in their size, drive, and independence. First-time dog owners often underestimate how much structured exercise and mental engagement this breed needs to avoid destructive behavior at home.
9. English Setter
Four setter breeds, the English Setter, Irish Red and White Setter, Irish Setter, and Gordon Setter, combine beauty, brains, and bird sense as breeds of the AKC Sporting Group that double as loyal family companions and talented field canines. The English Setter is one of four British setters recognized by the AKC, developed 400 to 500 years ago to hunt across the diverse terrains of England, Ireland, and Scotland according to the English Setter Association of America.
These stylish sporting dogs silently locate birds living mainly on the ground, such as quail, pheasant, and grouse, lifting their heads and pointing their noses skyward rather than running after the birds once they go airborne. The breed’s silky, flecked coat (called “belton” by fanciers) comes in blue, orange, lemon, and liver patterns.
10. Gordon Setter
The largest and darkest of the setter breeds, the Gordon Setter wears a glossy black-and-tan coat that distinguishes it instantly from its lighter-colored cousins. The AKC officially recognized the breed in 1884 and changed its name from Gordon Castle Setter to Gordon Setter in 1892.
The American and Canadian Kennel Clubs classify this breed, like the other three setters, within the Sporting Group, though setters from show lines tend to run heavier and larger than those bred for working field trials. Gordon Setters hunt with a methodical, deliberate pace rather than the ground-eating speed of an English Setter.
11. Irish Setter
The Irish Setter developed in the 19th century in Ireland, where it was bred to have a strong sense of smell and agility, and this fast breed excels at covering lots of flat ground. It is well known for its red coat, though the original breed had a red-and-white coat before the white was bred out, and the glossy coat repels water while helping keep the dog dry.
The Irish Setter was officially recognized by the AKC in 1878, making it one of the older setter breeds in the registry. Modern field-bred Irish Setters retain strong hunting drive, though show-line dogs are often bred more for their mahogany coat than working ability.
12. Irish Red and White Setter
Frequently mistaken for a poorly marked Irish Setter, this is actually a distinct and older breed. From the 1600s on, the Irish Red and White Setter was a fixture of Ireland’s hilly countryside, and though the dogs nearly went extinct during and after World War I, the breed was revived in the 1920s.
Common Mistake: Assuming the Irish Red and White Setter is simply an Irish Setter with white markings. The Irish Red and White Setter is a cousin to the Irish Setter but is shorter and stockier, with a fun-loving, energetic personality that’s loyal to family around the house.
Classified in the Gundog Group by the Kennel Club in the UK and the Sporting Group by the American and Canadian Kennel Clubs, the breed still has an ingrained natural working ability that shows when correctly trained. Full AKC recognition came in 2009, making it one of the more recently formalized setter breeds in America.
13. Spinone Italiano
Italy’s contribution to the versatile pointing world, the Spinone Italiano carries a dense, wiry coat in shades of white, orange-roan, or brown-roan. This section opens a cluster of less common European all-rounders bred to hunt, point, and retrieve across varied terrain, summarized below for quick comparison.
| Breed | Country of Origin | Coat Type | Primary Strength |
|---|---|---|---|
| Spinone Italiano | Italy | Wiry, dense | Slow, methodical pointing in heavy cover |
| Bracco Italiano | Italy | Short, glossy | Wide-ranging scent work on upland birds |
| Braque d’Auvergne | France | Short, fine | Steady pointing over mixed terrain |
| Pudelpointer | Germany | Wirehaired or flat | Water retrieving and fur-and-feather versatility |
| Large Munsterlander | Germany | Long, feathered | All-around HPR farm and field work |
| Small Munsterlander | Germany | Medium, feathered | Compact versatility for small-game hunters |
| Wirehaired Pointing Griffon | Netherlands/France | Wiry, coarse | Slow-paced pointing suited to close cover |
| Drentsche Patrijshond | Netherlands | Medium, feathered | Old-world Dutch partridge dog versatility |
Its gentle, patient temperament makes the Spinone a favorite among hunters who also want a calm household companion. The breed moves at a slower, more deliberate pace afield than many British pointing breeds, trading speed for thoroughness in thick brush.
14. Bracco Italiano
One of the oldest pointing breeds in existence, the Bracco Italiano traces its lineage back centuries in Italy, predating many of the more famous British and German pointing lines. Its short coat comes in white-and-orange or white-and-chestnut patterns, and its large, drooping ears give it an unmistakably houndish look for a pointing breed.
The Bracco ranges widely when hunting open country but adapts its pace to denser cover, a trait valued by hunters who work varied terrain in a single outing. Despite its working history, the breed is known for a calm, affectionate temperament at home.
15. Braque d’Auvergne
A regional French pointing breed rarely seen outside Europe, the Braque d’Auvergne wears a short black-and-white coat with a distinctive solid black head. It developed in the Auvergne region of France specifically for upland bird hunting over rolling farmland.
Steady and methodical rather than flashy, this breed holds a point reliably and works well with a single hunter rather than in large hunting parties. Its rarity in the United States means most American hunters will never encounter one outside specialty import kennels.
16. Pudelpointer
True to its name, the Pudelpointer descends from a cross between Poodles and English Pointers, combining the Poodle’s water tolerance and trainability with the Pointer’s bird sense. German breeders developed the cross in the late 19th century to produce a single do-everything gun dog.
Important Note: Pudelpointer litters remain small in the United States, and most puppies come from parents that have already proven themselves in field testing, which keeps working ability consistently high across the breed compared to more mass-produced hunting breeds.
The breed’s coarse, weather-resistant coat sheds minimal hair, and its calm, biddable temperament makes training straightforward compared to some higher-strung pointing breeds.
17. Large Munsterlander
Despite its name suggesting a small or medium build, the Large Munsterlander is a substantial, black-and-white German pointing breed developed from Small Munsterlander stock combined with longhaired pointer lines. It was originally excluded from German pointer breed clubs for not meeting coat-color standards, which pushed early breeders to formalize it as its own distinct breed.
This dog excels at both upland pointing and water retrieving, and its striking black-and-white coat makes it easy to spot in tall grass or dense brush. Temperament runs affectionate and biddable, traits that transfer well to family life outside hunting season.
18. Small Munsterlander
Smaller and more compact than its Large Munsterlander cousin, this German breed carries a brown-and-white coat with feathering similar to a spaniel. It was developed as a farmer’s all-purpose hunting dog, valued for versatility over raw speed or range.
The Small Munsterlander suits hunters who want a dog capable of handling upland birds, waterfowl, and even small fur-bearing game without needing multiple specialized breeds. Its moderate size and biddable nature also make it a practical choice for hunters without access to large tracts of land.
19. Wirehaired Pointing Griffon
Developed in the Netherlands by a breeder determined to create the ultimate “supreme gun dog,” the Wirehaired Pointing Griffon carries a distinctive double coat with a harsh outer layer and dense undercoat. Its shaggy eyebrows and beard give it an almost comical, grandfatherly expression that belies serious hunting ability.
This breed moves at a slower, more careful pace than flashier pointing breeds, which suits hunters working thick, thorny cover where a dog needs to pick its way through rather than cover ground at a gallop. Its calm temperament and moderate exercise needs make it more adaptable to family life than many higher-drive pointing breeds.
20. Drentsche Patrijshond
One of the rarest breeds on this list outside the Netherlands, the Drentsche Patrijshond (literally “Drent partridge dog”) has hunted alongside Dutch farmers for centuries. Its medium-length, feathered coat comes in brown-and-white or orange-and-white patterns similar to a spaniel’s.
The breed remains almost entirely unknown in American hunting circles, with most representatives found in Dutch and Belgian kennels. Those who do own one in the United States typically acquired dogs through direct import rather than domestic breeders.
21. Labrador Retriever
Retrievers are bred to mark falling birds, remember multiple falls, and return game undamaged to hand, which has made them the dominant waterfowl dog in North America and among the most popular breeds overall. The Labrador Retriever, Golden Retriever, Chesapeake Bay Retriever, Flat-Coated Retriever, Curly-Coated Retriever, and Nova Scotia Duck Tolling Retriever are the AKC-recognized retriever breeds covered in this guide.
| Breed | Best Suited For | Coat |
|---|---|---|
| Labrador Retriever | All-around upland and waterfowl retrieving | Short, dense, water-repellent |
| Golden Retriever | Family-friendly retrieving and tracking | Long, wavy, feathered |
| Chesapeake Bay Retriever | Cold-water waterfowl retrieving | Harsh, oily, wavy |
| Flat-Coated Retriever | Versatile upland and water work | Flat, silky, single layer |
| Curly-Coated Retriever | General-purpose bird retrieving | Tight curls, water-resistant |
| Nova Scotia Duck Tolling Retriever | Decoy luring and small-water retrieving | Medium, water-repellent |
Labrador retrievers have long been a favorite among Pheasants Forever members, though recent surveys show the German Shorthaired Pointer is now the most popular bird dog breed among its members, while Labs remain one of the most popular dog breeds in America overall. Their webbed feet and thick double coat make them equally comfortable retrieving pheasant on dry ground or ducks from icy water.
22. Golden Retriever
Originally bred in Scotland for retrieving shot waterfowl from both land and water, the Golden Retriever combines a soft mouth with an eager, biddable temperament that made it a natural fit for formal retriever training programs. Its flowing golden coat requires more grooming upkeep than a Labrador’s short coat.
Pro Tip: Field-bred Golden Retriever lines look noticeably leaner and more athletic than show-line dogs bred primarily for the conformation ring. Hunters seeking a working retriever should look for breeders who test dogs in hunt tests or field trials rather than relying on show titles alone.
Beyond hunting, the breed’s patience and trainability explain why it remains one of the most popular family dogs and service dogs in the country, a versatility few other sporting breeds can match.
23. Chesapeake Bay Retriever
Developed along the icy waters of the Chesapeake Bay in Maryland, this retriever carries a harsh, oily, wavy coat specifically evolved to withstand frigid water retrieves that would chill other breeds quickly. Its coloring ranges from dead-grass brown to a dark reddish-sepia, blending into marsh vegetation.
Chesapeakes are generally more independent and protective than Labradors or Goldens, traits that made them prized for solo waterfowl work with a single handler. Hunters chasing common duck breeds across open bays have relied on Chesapeakes for generations specifically because of their cold-water endurance.
24. Flat-Coated Retriever
Less common than the Labrador or Golden, the Flat-Coated Retriever carries a sleek, single-layer coat and a more playful, exuberant temperament than its popular cousins. The breed developed in 19th-century England from a mix of retriever and setter bloodlines.
Flat-Coats mature more slowly than most sporting breeds, often retaining puppy-like energy into their third year, which can test the patience of hunters expecting an early-finished working dog. Once mature, the breed handles both upland flushing work and water retrieves with equal enthusiasm.
25. Curly-Coated Retriever
Originating in England in the 19th century, the Curly-Coated Retriever was first bred as a general-purpose bird-hunting dog. Its tight, water-resistant curls cover the entire body except the face and front legs, giving it the most distinctive coat of any retriever breed.
Taller and more independent-minded than the Labrador, the Curly-Coated Retriever tends to think through commands rather than respond instantly, a trait some trainers find frustrating and others find refreshing. The breed remains relatively rare in American hunting camps compared to its more mainstream retriever cousins.
26. Nova Scotia Duck Tolling Retriever
The smallest of the AKC retriever breeds, the “Toller” earned its name from a unique hunting technique: the dog plays and frolics along the shoreline to lure curious waterfowl within gun range before the hunter takes the shot. Its red-and-white coat mimics the fox, which may be part of why ducks find the dog’s movements so intriguing.
Listed among the lesser-known Sporting Group breeds that many hunters may not recognize by name, the Toller has nonetheless built a devoted following for its compact size, intelligence, and strong retrieving drive packed into a dog under 50 pounds.
27. English Springer Spaniel
Spaniels work close to the hunter, quartering methodically through cover to flush birds within shotgun range, and are versatile dogs capable of working upland birds, flushing waterfowl from heavy cover, and retrieving. The English Springer Spaniel is the most widely used spaniel in upland hunting work in the United States, making it the natural lead-in to this spaniel cluster.
| Breed | Size | Coat Notes |
|---|---|---|
| English Springer Spaniel | Medium, 40-50 lbs | Long ears, liver/black and white |
| American Cocker Spaniel | Small, 20-30 lbs | Silky, flowing coat |
| English Cocker Spaniel | Medium, 26-34 lbs | Shorter, less profuse coat than American line |
| Clumber Spaniel | Large, 55-85 lbs | Dense white coat with lemon markings |
| Field Spaniel | Medium, 40-55 lbs | Flat, silky, solid colors |
| Sussex Spaniel | Medium, 35-45 lbs | Golden-liver, wavy coat |
| Welsh Springer Spaniel | Medium, 35-55 lbs | Red and white, weatherproof |
| Boykin Spaniel | Small-medium, 25-40 lbs | Curly or wavy, solid brown |
| American Water Spaniel | Small-medium, 25-45 lbs | Curly, liver or chocolate |
| Irish Water Spaniel | Large, 45-68 lbs | Tight curls, topknot, solid liver |
English Springer Spaniels are medium-sized dogs weighing around 40 to 50 pounds, with long fur mixed with colors like black, tan, and liver, plus characteristically long ears that hang on the side of their heads. Their quartering search pattern, working back and forth in front of the hunter, remains the model other flushing breeds are judged against.
28. American Cocker Spaniel
Though best known today as a show ring and family favorite, the American Cocker Spaniel’s roots trace directly back to flushing spaniel work in the field. Over the 20th century, American breeders selected for a smaller frame and more profuse coat than its English ancestors carried, gradually shifting the breed’s emphasis away from hunting toward companionship.
A small but dedicated group of hunters still maintains field-bred lines of the American Cocker, and these dogs retain the instinct to flush and retrieve small upland birds despite decades of divergence from their working cousins. The breed’s smaller size suits hunters working thick, low brush where a larger spaniel would struggle.
29. English Cocker Spaniel
Closer to its working roots than the American Cocker Spaniel, the English Cocker Spaniel retains a leaner frame and shorter coat better suited to active field work. The two breeds share a common ancestor but split into distinct standards once American and British breeders pursued different priorities for size and coat.
English Cockers hunt with the same close-working, methodical quartering style as other flushing spaniels, covering ground efficiently in front of the gun. Their moderate size and manageable coat make them a practical choice for hunters who want spaniel versatility without extensive grooming demands.
30. Clumber Spaniel
The heaviest and most deliberate of the AKC spaniel breeds, the Clumber Spaniel moves at a slow, methodical pace through cover rather than the bouncing energy seen in Springers or Cockers. Its substantial bone structure and dense white coat trace back to French and English aristocratic kennels of the 18th century.
Clumbers work best in situations where thoroughness matters more than speed, such as hunting heavy brush where a fast-moving dog might push past hidden birds. The breed’s calm, dignified temperament extends from the field to the living room, where it tends toward a relaxed, low-key presence.
31. Field Spaniel
The original Spaniel breed was divided into Springer and Field Spaniels, and Field Spaniels became known first as Cocking Spaniels and then as Cocker Spaniels before the modern breed distinctions solidified. Today’s Field Spaniel occupies a narrower niche than its Springer or Cocker relatives, bred for a calm, deliberate flushing style in solid-colored coats of black, liver, or roan.
The breed remains one of the rarer AKC Sporting Group members, with far fewer registrations than Springers or Cockers. Hunters who do work with Field Spaniels generally praise their steady temperament and willingness to work methodically rather than frantically through cover.
32. Sussex Spaniel
Named for Sussex County, England, this low-slung, heavily built spaniel carries a distinctive golden-liver coat unlike any other spaniel breed. Its slower, more deliberate pace in the field reflects its heavier build compared to the leaner Springer or Cocker lines.
The Sussex Spaniel has one of the smallest registration numbers in the entire AKC Sporting Group, making it a genuinely rare sight both in the show ring and in the field. Its distinctive deep-toned bark while trailing game is considered a breed hallmark by longtime fanciers.
33. Welsh Springer Spaniel
Distinct from the English Springer despite the shared name, the Welsh Springer Spaniel carries a rich red-and-white coat and developed independently in Wales rather than England. Genetic studies have suggested the breed may actually predate its English counterpart by a considerable margin.
Welsh Springers hunt with a close, active working style suited to the rugged Welsh countryside that shaped the breed. Their moderate size and weatherproof coat make them capable of handling both upland flushing duties and light water retrieving work.
34. Boykin Spaniel
Boykins are a newer spaniel breed in the AKC’s Sporting Group, originally bred in South Carolina in the early 20th century, because hunting along the Wateree River Swamp required travel in small boats and the larger dogs typically used for hunting, like Labrador Retrievers, were too big for the boats.
Key Insight: The Boykin Spaniel holds official recognition as South Carolina’s state dog, a distinction that speaks to its deep regional roots as a swamp and marsh hunting specialist developed specifically to fit small johnboats.
Its solid brown, curly-to-wavy coat and compact build let it move easily through dense wetland cover while still carrying enough stamina for a full day of dove or turkey hunting alongside traditional duck work.
35. American Water Spaniel
Developed in the upper Midwest, likely Wisconsin, the American Water Spaniel was bred by hunters who needed a smaller, boat-friendly retriever-flusher hybrid for working rivers and marshes from small craft. Its tightly curled, liver or chocolate coat resists water effectively despite the breed’s modest size.
This breed blends spaniel flushing instincts with genuine retrieving ability, giving it a dual-purpose skill set uncommon among the purely flushing spaniel breeds. It remains one of the rarer American-developed sporting breeds, with far smaller registration numbers than its Boykin or Springer cousins.
36. Irish Water Spaniel
The tallest of the spaniel breeds, the Irish Water Spaniel is easily identified by its tight, curly topknot and solid liver-colored coat covering a lean, athletic frame. Its curled tail, nicknamed the “rat tail” for its smooth, hairless tip, is a breed hallmark that distinguishes it from every other spaniel.
Developed in Ireland for retrieving waterfowl from cold lakes and rivers, the breed combines genuine retrieving power with the close-working flush instincts typical of spaniels. Its intelligence and independent streak mean training sessions benefit from variety, since the breed tends to lose interest in repetitive drilling faster than more biddable retriever breeds.
Choosing among these 36 bird dog breeds comes down to matching a dog’s working style, coat, and energy level to the actual terrain and game a hunter pursues most often. Pointers and setters suit open-country upland work, the European versatile breeds fit hunters who want one dog for everything, spaniels excel in thick cover close to the gun, and retrievers remain unmatched for waterfowl recovery. For hunters exploring other working dog categories, breeds built for farm and livestock work, such as those covered in this guide to herding dog breeds, offer a useful point of comparison in how purpose-driven breeding shapes temperament and structure.