Frequency signatures: Wreathed Hornbill to Yellow-legged Gull
Each card gives a species’ behavioural archetype, its frequency — how often it commits effort and how long each commitment lasts — and a waveform tracing that rhythm.
Frequency signatures
Each waveform traces one species’ working rhythm — where it spends effort, and where it waits. 2.327 species, A–Z; showing 2.281–2.304.
Wreathed Hornbill
A Female Walled Inside
The female entering a natural tree cavity and sealing the entrance to a narrow slit with mud, droppings and fruit pulp • Remaining sealed inside for months, moulting her flight feathers while incubating and brooding • The male passing every item of food through that slit for the whole period
Because the cycle is annual, it operates as a low-frequency system.
Wrybill
Asymmetric Stone-Edge Feeder
Rhythmic • Precise • Forager
That anatomy and foraging pattern produce a mid-frequency system: a repeated, coordinated search-and-probe cycle tuned to the structure of the riverbed.
X-marked Snouted Tree Frog
Chorus Switched On by Rain
Sheltering • Nocturnal • Waiting
That makes it a bimodal system: quiet sheltering and rain-triggered chorusing.
X-ray Tetra
Pigment-Free Body Screen
Schooling • Translucent • Coordinated
That makes it a mid-frequency system: rhythmic and coordinated, where safety comes from being unresolvable rather than from speed or defence.
Xantus's Hummingbird
Nectar-Fuelled Torpor Cycle
Hovering • Circuiting • Expensive
Because a maximum-rate daytime mode alternates with a genuinely suppressed nocturnal state, this is a bimodal system.
Xantus's Murrelet
Darkness-Only Colony Attendance
Nocturnal • Offshore • Continuous
Because colony attendance and offshore feeding alternate on a steady nightly rhythm rather than in bursts, it is a mid-frequency system.
Xeme
Nesting Behind Somebody Else's Anger
Tundra pools • Crossing the equator • Feeding at sea
Continuous seasonal travel and feeding makes this a mid-frequency system.
Yacare Caiman
Bone Plates as a Chemical Reserve
Floating still • Taking small fish • Holding position
Yacare reach some of the highest densities of any crocodilian on earth in the Pantanal, taking small fish constantly rather than rarely, which makes this a low-frequency system.
Yangtze Finless Porpoise
Narrow-Beam Echolocation in Silt
Clicking • Turbid • Continuous
Because emitting and listening run continuously at a rapid rate, it is a mid-frequency system.
Yellow Anaconda
Mass the Water Carries
Submerged • Supported • Eyes-up
That makes it a bimodal system: prolonged submerged waiting and a heavy committed strike.
Yellow Boxfish
Bony Box Steered by Small Fins
Cruising • Grazing • Armoured
That makes it a single, mid-frequency system.
Yellow Dung Fly
Waste-Margin Foraging Circuit
Circuit • Cue-led • Repeating
That makes the dung fly a mid-frequency system: a rhythmic, cue-led operator built around ongoing activity on an overlooked but regularly renewed resource.
Yellow Mongoose
Shared Burrow Radius
Radiating • Solitary • Tethered
That makes it a mid-frequency system: steady, repeated outward trips anchored to one fixed point.
Yellow Sac Spider
A Bite Credited Too Much
A spider that builds a silk retreat rather than a web and hunts on foliage at night • A bite that is genuinely painful and occasionally causes local reactions, delivered when the animal is pressed against skin • Necrotic lesions widely attributed to this species and repeatedly shown on investigation to have other causes, so the reputation far exceeds the evidence
Because encounters are rare, it operates as a low-frequency system.
Yellow Tang
A Fishery Closed by Law
Grazing filamentous algae across Hawaiian reef all day • Being collected in enormous numbers for the marine aquarium trade • Having that trade halted by litigation rather than by biology
Since grazing is continuous, it operates as a mid-frequency system.
Yellow-banded Caecilian
Ring-Muscle Soil Ram
Burrowing • Chemosensing • Hidden
Because everything is arranged for slow continuous work in a medium nothing else exploits, it is a low-frequency system.
Yellow-banded Millipede
A Wave Down the Legs
Dozens of leg pairs each stepping slightly later than the one in front • The resulting pattern travelling backwards along the body as a continuous visible wave • Many legs always in contact with the ground, producing steady force rather than the alternating push of a few
Because the wave repeats many times a second, it operates as a high-frequency system.
Yellow-billed Shrike
Group-Held Perch Coverage
Spread across perches • Watching different ground • Feeding each other's young
Because the watching and feeding run together through daylight, it operates as a mid-frequency system.
Yellow-billed Stork
Open Bill, Stirring Foot
Wading • Stirring • Triggered
That makes it a mid-frequency system: a continuous sweeping search with a very fast automatic closure on contact.
Yellow-crowned Amazon Parrot
A Voice Always Changing
A vocal organ with two independently controlled sides producing sounds without lips or teeth • Neural circuitry for vocal learning that stays open through adult life rather than closing after a juvenile period • New sounds acquired and added at any age, including those of entirely different species
Because learning and calling are continuous, it operates as a mid-frequency system.
Yellow-crowned Night Heron
Crab-Crushing Tidal Foraging
Wading slowly • Seizing • Breaking the shell
Because that foraging is sustained and repeated on every workable tide, it operates as a mid-frequency system.
Yellow-footed Rock-wallaby
Cliff-Edge Balance Engine
Sheltered • Cautious • Reset
This creates a bimodal rhythm: low-frequency sheltering and recovery anchored to the rocks, and a moderate, repeatable cliff-hopping mode that trades raw speed for precise, recoverable movement along dangerous terrain.
Yellow-footed Tortoise
A Slow Gut Moving Big Seeds
Walking the forest floor • Swallowing fruit whole • Passing seeds days later
This is a low-frequency system.
Yellow-legged Gull
A Gull That Hunts Seabirds
Patrolling seabird colonies rather than foraging at sea • Taking eggs, chicks and adults of smaller species • Robbing food from birds returning to feed their young
Since foraging events recur constantly, it operates as a mid-frequency system.