*Oology is a branch of ornithology studying bird eggs, nests and breeding behaviour. The word is derived from the Greek oion, meaning egg.

41. Double-crested Cormorant

This part of the Stanislaus Audubon Website is focused on 44 common Central Valley nesting species with background about their nesting habits. Please check the Great Valley Museum Central Valley Egg Collection starting page for links to all the featured species.

DOUBLE-CRESTED CORMORANT NESTING INFORMATION (From birdsoftheworld.org)

Nests - The male chooses the nest site and then attracts a female. Nests can be on the ground, on rocks or reefs with no vegetation, or atop trees, which may be alive when a cormorant colony first forms but typically die after a few years from the guano build-up. Nests are 1.5 to 3 feet in diameter and 4 to 17 inches high; ground nests tend to be wider than tree nests, but tree nests have deeper interiors. Nests are built in the center of a colony first, then expand outward.
Eggs - Elongate ovate to cylindrical ovate. Shell pale blue, unmarked, but pigmented layer often obscured by variable outer calcite cover that is initially white and very porous. Clutch size usually 3 to 4 (range 1 to 7).
Incubation - Both sexes incubate for 25-33 days.
Fledging - Altricial hatchling is feeble, barely able to move limbs stiffly, lift head and move it from side to side; naked, with shiny, brown translucent skin. Young leave ground nests at 3–4 wk, when they are well feathered, but 2–3 wk before flying.

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