Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said: "Taking evil omens from birds is shirk (associating partners with Allah), and there is none of us but (some of it occurs to him), but Allah, the Mighty and Majestic, removes it through reliance (upon Him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16517