What are the bad omens associated with birds?

Here is a basic list, not complete by any means but a very good start.

Blackbird: A message of blessings.

Bluebird: Happiness.

Corncrake: A warning of misfortune to come.

Crane: Independence, cessation of combat .

Crow: Divine law.

Curlew: Storm Bringer.

Dove: Luck in Love. Love, peace & gentleness

Duck: Good Luck. Wealth

Eagle: Divine Spirit. To see an eagle is to have divinity touch your life. Flamingo: Awareness.

Goose: Faithfulness, communication, & travel

Grouse: Sacred Spiral.

Gull: Adaptability.

Hawk: Messenger. If you see a hawk, look around, there is a message for you in what is also going on around you.

Hen: Domesticity. Hens also predict the weather; if they gather on a mound and preen their feathers, rain is on the way. Also if it starts to rain watch your hens if the huddle under shelter, the rain will be of short duration, if they go out into it, the rain will last most of the day.

Heron, blue: Rhythm and balance

Hummingbird: Joy Miracles

Kingfisher: Predicts a magical experience.

Lark: Great happiness.

Loon: Solitude.

Magpie: Fortune-teller.

Nightjar: Illness.

Ostrich: Fickleness.

Owl: Wisdom. Visions.

Parrot: Mimic. Ostentatiousness.

Peacock: Pride. Vanity.

Pelican: Watchfulness.

Penguin: Playfulness.

Pheasant: Confidence

Raven: Magic. When you see ravens you may be about to experience a change in consciousness.

Road-runner: Cleverness.

Robin: Gypsies see robins as a bringer of good luck.

Rook: Good Luck.

Rooster: Pride.

Stork: Its German name adebar means "luck bringer", and a stock perching on your house indicates very good fortune.

Sparrow: Good luck for lovers.

Swallow: Good fortune.

Swan: Grace.

Turkey: Give away. Amerinds see turkey as a sign of generosity.

Vulture: Poverty. Serious disruption in your life.

Wagtail: Good luck.

Woodpecker: Guardian.

Wren: Bringer of good luck