Ostrich Intruder
The Ostrich Intruder is a modern, aggressive streamer pattern designed to trigger violent strikes from large, predatory fish. Part of the intruder family of flies developed for steelhead fishing, this pattern has proven equally effective for trophy trout, particularly during fall and winter when large fish become increasingly aggressive and territorial. The pattern's name comes from its use of ostrich herl, which provides exceptional movement and a lifelike pulsing action in the water. Intruder-style flies are characterized by their long, flowing materials, articulated construction, and aggressive profile. They're designed to intrude on a fish's territory and provoke a reaction strike rather than simply imitate a food source. The Ostrich Intruder exemplifies this philosophy with its oversized profile, contrasting colors, and materials that create maximum movement with minimal effort from the angler. The ostrich herl used in this pattern is key to its effectiveness. These long, webby fibers undulate with the slightest current or movement, creating a pulsing, breathing appearance that suggests life. The fibers are translucent, allowing light to pass through and creating subtle color shifts. When combined with flash materials like Flashabou or Ice Dub, the pattern creates an irresistible combination of movement, color, and sparkle. The Ostrich Intruder is particularly effective during fall spawning periods when large brown trout, rainbow trout, and bull trout become aggressive and territorial. These fish will attack intruder patterns out of territorial aggression even when not actively feeding. The pattern is also deadly for winter steelhead, which respond aggressively to large, dark patterns swung through runs and pools. Fishing the Ostrich Intruder requires different techniques than traditional streamers. It's most effective when swung on a sink-tip or full-sinking line, allowing the current to impart action to the materials. The angler casts across and downstream, allows the fly to swing through the run, then takes a step or two downstream and repeats. This methodical covering of water is especially effective for steelhead and migratory trout.
Pattern Details
- Type
- Streamer
- Seasons
- fall, winter
- Hook Sizes
- #2-6
- Hook Type
- Articulated intruder hook or trailing hook system
- Tying Difficulty
- Advanced
- Imitates
- Large baitfish, leech
Recipe & Materials
- Hook
- Intruder trailer hook, sizes 2-6
- Shank
- Articulated shank or wire
- Thread
- 3/0 or 140 denier (black)
- Tail
- Ostrich herl (black, purple, or dark)
- Body
- Wrapped ostrich herl
- Flash
- Flashabou or Ice Dub
- Wing
- Layers of ostrich herl
- Collar
- Schlappen or soft hackle
- Head
- Dubbing or thread (dark)
- Eyes
- Bead chain or dumbbell (optional)
Technique & Presentation
Tying intruder patterns requires understanding articulated hook systems. Most Ostrich Intruders are tied on a rigid wire shank with a trailing hook attached via monofilament or wire loop. This articulation creates lifelike movement and reduces leverage that allows fish to throw the hook. Begin by securing your trailing hook to the shank using the loop method or tube attachment.
Build the tail using long ostrich herl, allowing it to extend well beyond the hook point. The tail should be substantial—use multiple strands to create a full, flowing appearance. Add flash materials evenly distributed through the ostrich for added attraction. The body is wrapped with additional ostrich herl, creating a thick, buggy underbody.
The wing is built in layers, each slightly longer than the previous, creating depth and movement. Use ostrich herl in varying shades—often black or purple with accents of lighter colors like blue or UV purple. Between layers, add flash materials. The collar is tied from schlappen or large soft hackle feathers, wrapped to create a full, breathing profile.
The head should be substantial, built from dubbing or thread, and can include weighted eyes if you want the pattern to dive deeper. Some tiers prefer cone heads for added weight and attraction. The key is creating a pattern that pushes water, creates vibration, and looks alive with minimal input from the angler.
Fish the Ostrich Intruder on a two-handed rod or single-hand rod with sink-tip line. Cast across the current and allow the fly to swing downstream, maintaining tension but avoiding excessive stripping. The current and sink rate will provide all the action needed. Strikes are often violent—steelhead and large trout will absolutely crush intruder patterns. Keep steady tension and be ready for explosive takes.
History & Origin
The intruder style emerged from the Pacific Northwest steelhead fishing community in the early 2000s. Innovative tiers like Ed Ward and Scott Howell developed these patterns to target aggressive winter steelhead in large, powerful rivers. The intruder philosophy departed from traditional steelhead flies by emphasizing aggression and movement over precise imitation.
The Ostrich Intruder specifically gained popularity as tiers experimented with different materials for creating movement and bulk. Ostrich herl proved ideal—readily available, relatively inexpensive, and providing exceptional action in the water. The pattern quickly crossed over from steelhead to trophy trout fishing, where guides and serious anglers recognized its effectiveness for triggering reaction strikes from large, territorial fish.
The modern streamer revolution, popularized by anglers like Kelly Galloup, has further elevated the intruder style. Today's trout anglers increasingly employ techniques borrowed from steelhead fishing—swinging large flies, targeting specific lies, methodically covering water. The Ostrich Intruder represents this evolution, a pattern designed not to match the hatch but to provoke the most aggressive response from the largest fish in the system.
Where to Fish This Fly
Related Streamer Patterns
Woolly Bugger
If you could only fish one fly for the rest of your life, many guides would choose the Woolly Bugger. It imitates leeches, baitfish, crayfish, and large nymphs. Strip it, swing it, dead-drift it; the Woolly Bugger catches fish everywhere. The Woolly Bugger is the Swiss Army knife of fly fishing. Its marabou tail undulates seductively with the slightest current or rod-tip movement, its palmered hackle body creates a buggy, lifelike profile, and its overall shape suggests a wide range of aquatic prey items. Whether a trout sees it as a leech, a sculpin, a crayfish, a large stonefly nymph, or a small baitfish, the result is the same: they eat it. The Woolly Bugger is effective in still water and moving water, in clear conditions and dirty water, in winter and summer. In Montana, the Woolly Bugger is the pattern you tie on when nothing else is working, or when everything is working and you want to catch bigger fish. A black Woolly Bugger stripped along the banks of the Madison or Yellowstone will draw strikes from brown trout that ignore all other offerings. Olive and brown versions excel on tailwaters. White Woolly Buggers fished deep on sinking lines can produce the largest fish of the day. No Montana fly box is complete without a selection of Woolly Buggers in black, olive, brown, and white, in sizes #4 through #10.
Sculpzilla
A simple sculpin imitation that swims with an enticing undulating action. The Sculpzilla is less flashy than articulated streamers but deadly effective. Fish it on a short-line swing or strip it along the banks for aggressive brown trout. The Sculpzilla is a masterclass in effective simplicity. While the streamer world has trended toward ever-larger, ever-more-complex articulated patterns, the Sculpzilla proves that a well-designed single-hook fly can be just as effective. The pattern uses a minimal number of materials (primarily a wool head and marabou or rabbit strip body) to create a sculpin profile that rides hook-point-up and swims with a natural, undulating motion that perfectly mimics a sculpin darting along the bottom. Sculpins are a critical forage species in Montana's trout rivers. These bottom-dwelling baitfish are found in every stream and river in the state, and they are a preferred food item for large brown trout. The Sculpzilla's hook-up design allows it to be bounced along rocky bottoms without snagging, putting it right in the zone where sculpins live. On the Madison, Yellowstone, and Missouri rivers, the Sculpzilla consistently produces large trout that have learned to associate the sculpin silhouette with an easy, protein-rich meal.
Sex Dungeon
Kelly Galloup's articulated streamer is designed to provoke territorial aggression from large brown trout. This big, flashy fly pushes water and triggers reaction strikes. Fish it on sinking tips along cut banks and boulder structure. The Sex Dungeon is not designed to be eaten; it is designed to be attacked. Kelly Galloup, the master of the modern streamer game, created this pattern specifically to trigger the territorial aggression of large brown trout. With its articulated body, marabou tail, flash-infused profile, and pulsating materials, the Sex Dungeon pushes water and creates a commotion that demands a response from any predatory fish in the vicinity. The fly does not need to closely match any specific baitfish; it needs to intrude on a trout's territory and provoke a violent reaction. Fishing the Sex Dungeon is a fundamentally different experience from nymph or dry fly fishing. You are hunting, not waiting. You are casting to specific pieces of structure (undercut banks, logjams, boulder gardens, deep slots) where large trout establish territories. The strike, when it comes, is explosive: a flash of brown and gold, a savage pull, and the fight of a lifetime. On Montana's premier brown trout rivers (the Madison, the Yellowstone below Livingston, and the lower Missouri) the Sex Dungeon is the pattern that unlocks access to the biggest fish in the river.
Zuddler
A versatile sculpin-meets-Muddler pattern that works fished slow or fast, deep or shallow. The spun deer hair head creates surface disturbance when stripped and can be dead-drifted like a large nymph. The Zuddler occupies a unique niche in the streamer world as a fly that can be fished effectively at virtually any speed and depth. Its spun and clipped deer hair head, borrowed from the classic Muddler Minnow, gives it buoyancy and creates a water-pushing action when stripped. Below the head, a zonker strip body and marabou tail provide the movement and lifelike action of modern streamer designs. This combination of old-school and new-school elements makes the Zuddler one of the most versatile streamers available. The Zuddler's versatility is its greatest asset on Montana rivers. Fish it with an aggressive strip on a floating line to create a wake that draws explosive surface strikes. Fish it on a sink-tip with a slow retrieve to work it through deeper structure. Dead-drift it through a run like an oversized nymph for trout that are not in an aggressive mood. This ability to adapt to conditions and fish mood makes the Zuddler an excellent choice when you are not sure what the fish want. On the Madison and Yellowstone, where conditions can change throughout the day, having a fly that adjusts with you is invaluable.
Black Woolly Bugger
The Black Woolly Bugger stands as arguably the most versatile and universally effective fly pattern ever created. This simple yet deadly streamer imitates leeches, baitfish, sculpins, crayfish, and large aquatic insects—essentially anything meaty that trout, bass, and other gamefish feed on. If forced to fish with only one fly for the rest of their lives, countless anglers would choose the Black Woolly Bugger without hesitation. The pattern's effectiveness comes from its lifelike movement in the water. The soft marabou tail undulates with even the slightest current, creating the illusion of a living creature swimming or struggling. The palmered hackle along the body adds additional movement while creating a buggy, substantial silhouette. When stripped through the water, the Woolly Bugger pulses and breathes like prey, triggering aggressive strikes from predatory fish. Black is the classic color and often the most productive, especially in off-color water, low light conditions, or when imitating leeches. The pattern excels in fall and winter when trout become more aggressive and feed heavily on larger prey items to build reserves. It works in every water type imaginable—from tiny mountain brooks where size 8 versions take wild trout, to large tailwaters and reservoirs where size 4 monsters draw crushing strikes from trophy fish. Fishing techniques vary widely: dead-drift it like a nymph through deep runs, strip it erratically like a fleeing baitfish, swing it on a tight line through pools, or even skate it across the surface. The Woolly Bugger produces at all depths and speeds, making it the ultimate searching pattern when you're uncertain what fish are feeding on or where they're holding.
Egg Sucking Leech
The Egg Sucking Leech is an audacious pattern that combines two of the most effective subsurface offerings in one fly: a leech imitation and an egg. This Alaskan-born pattern was designed to target aggressive rainbow trout and char feeding in spawning areas, but has proven deadly across the continent for any trout species. The garish combination of a dark leech body with a bright orange or pink bead head creates an irresistible target that triggers both predatory and egg-feeding instincts. Despite its somewhat comical name, the Egg Sucking leech represents a real feeding behavior. During salmon and trout spawning periods, leeches are attracted to spawning redds where they feed on dislodged eggs. Trout quickly learn that a dark, undulating shape near spawning areas often means an easy meal of both the leech and any egg it might be consuming. The pattern capitalizes on this association, presenting both food sources in one package. The fly works exceptionally well during fall, winter, and spring when various salmonid species are spawning. In rivers with fall salmon runs or spring rainbow spawns, the Egg Sucking Leech can be absolutely devastating. It's equally effective in tailwaters below dams year-round, where spawning activities occur throughout the seasons. The pattern also produces well in non-spawning periods simply as an attractor pattern, with the bright bead drawing attention in murky or deep water. This pattern has proven effective from Alaska's salmon streams to Montana's freestone rivers, Wyoming's tailwaters, Idaho's spring creeks, and throughout the Pacific Northwest. It works in Colorado's Gold Medal waters, California's Sierra streams, and even eastern waters like Pennsylvania's steelhead streams. The Egg Sucking Leech is particularly valuable in early season or high water conditions when visibility is reduced and trout respond to bold, visible flies. Fish it on a dead drift through deep runs, swing it through pools, or strip it erratically to imitate a fleeing leech.