Likely Great Cormorant (also called Great Black Cormorant); identification is tentative from this single, worn feather.

A dark, elongated feather found near the Beauly Firth in late September is consistent with a cormorant, but that location alone cannot confirm its source. Great Cormorants are large, dark, long-necked waterbirds that dive for fish and often rest with wings spread to dry.

Mostly dark brown-black, with a pale grey to whitish area at the base. Wear, damage, lighting, or feather overlap may affect the apparent pattern.

Pennaceous vane, but many barbs are separated, frayed, or missing; no obvious downy aftershaft is visible.

The long, dark rachis is prominent and appears fairly stiff; dark barbs are ragged along much of the vane, with pale basal material at one end.

The intact vane looks smooth and dark, but much of the feather is visibly frayed and disrupted rather than neatly interlocked.

Probably a wing feather, suggested by its length and narrow outline; precise position cannot be established.

Long dark shaft and vane, narrow shape, and pale damaged base fit a large waterbird flight feather; these traits are not diagnostic enough for certain species identification.

Great Cormorants use coasts, estuaries, lochs, and rivers, feeding in water and nesting colonially on cliffs, islands, or trees.

Widespread across Europe, including Scotland, with populations resident or locally dispersive; some northern birds move south in winter.

Cormorants are fish-eating predators in coastal and freshwater food webs. Great Cormorants are widespread, though local colonies can be affected by disturbance and changes in food supply.

European Shag feathers can also be dark; Great Cormorant is generally larger, but isolated worn feathers are difficult to separate. Other dark waterbird feathers may look similar.

Cormorants pursue fish underwater using powerful feet and can dive deeply; their conspicuous wing-spreading posture helps dry their plumage.

Cormorant feathers have no reliable species-specific cultural use identifiable here. Wild-bird feathers may be legally protected or regulated; avoid selling or keeping them without checking local rules.

Compare an intact specimen with measured reference feathers and inspect both sides, base, and vane symmetry. Near the firth, cormorants and shags are plausible sources, but habitat is supporting context, not proof.

Poor condition: substantial fraying and apparent vane loss; freshness, molt stage, and cause of damage cannot be determined from the image.

On the Beauly Firth near Inverness, Scotland in late September.