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White-bellied Sea-Eagle
Primary flight feather (remex), likely an outer primary (P8-P10)

White-bellied Sea-Eagle

Kingdom: Animalia, Phylum: Chordata, Class: Aves, Order: Accipitriformes, Family: Accipitridae, Genus: Haliaeetus, Species: Haliaeetus leucogaster

Family: Accipitridae (Hawks, Eagles, and Allies)

Shape
Highly asymmetrical with a distinctively narrow leading edge (outer vane) and a broader trailing edge (inner vane). The tip is tapered and pointed with significant emargination (notching) near the distal end.
Size
Estimated at 35-45 cm (14-18 inches) in length. The user description of 'bigger than a forearm' is consistent with the primary feathers of a large raptor having a wingspan of up to 2.2 meters.
Rarity
Common in suitable coastal habitats, though as a top predator, the absolute population density is lower than smaller birds.
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Description

This is a massive feather from Australia's second-largest bird of prey. The White-bellied Sea-Eagle is an iconic raptor with a white head, breast, and tail coverts contrastingly sharply against dark grey wings. In flight, it holds its wings in a distinct 'V' shape (dihedral).

Colour & Pattern

Uniformly dark slate-gray to brownish-black on the upper surface of the vane, characteristic of an adult bird. The rachis is remarkably pale, appearing creamy-white to light tan, which is a diagnostic feature for this species.

Barb Structure

Tightly interlocked pennaceous barbs throughout most of the vane to provide aerodynamic lift. The base shows a small amount of plumulaceous (downy) structure near the calamus. The barbs are stiff and resilient.

Texture & Surface

The surface is somewhat matte with a slight oily sheen, providing water resistance necessary for a maritime hunter. The texture is stiff and 'plasticky' due to the high keratin density required for large-raptor flight.

Key Features

Large size (30cm+), extreme asymmetry of the vanes, and most importantly, the stark contrast between the dark grey vane and the very pale/white central rachis.

Habitat

Coastal habitats, estuaries, large inland rivers, and terrestrial wetlands. Frequently found near Jervis Bay (Vincentia) roosting in tall trees overlooking the water.

Geographic Range

Found from India and Sri Lanka through Southeast Asia to Australia and Tasmania. It is a resident breeder across the Australian coastline.

Ecological Role

Apex predator and scavenger. They play a vital role in controlling populations of sea snakes, fish, and waterbirds. Their presence is an indicator of a healthy aquatic ecosystem.

Similar Species

Wedge-tailed Eagle feathers are similarly large but have a dark rachis and are generally more brownish. Osprey feathers have distinct banding/mottling which this feather lacks.

Interesting Facts

Pairs of Sea-Eagles often perform spectacular aerial displays where they lock talons and spin through the air in a 'cartwheel' before releasing just before hitting the water or ground.

Condition Notes

The feather appears to be a naturally molted specimen. There is some minor wear and 'zipper' separation at the trailing edge tip, but the rachis remains structurally sound and the color is well-preserved.

Notes

Found on a beach in vincentia NSW Australia Is bigger than my forearm