Migrating geese A flock of Canada geese fly in a V-formation during migration. (more) How Do Birds Know When to Fly South? Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/How-Do-Birds-Know-When-to-Fly-South Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Written and fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Apr 8, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot In the Northern Hemisphere, migratory birds tend to fly south to spend the winter in warmer locales. (Though in the Southern Hemisphere, migratory birds generally fly north for the winter.) Migratory birds know when to fly south for the winter due to a combination of internal physiological changes and external environmental cues. Migratory birds undergo physiological changes to prepare for migration. These changes are primarily controlled by the endocrine system, particularly the pituitary gland, which responds to variations in day length and other environmental factors. As the day length decreases in autumn, a bird’s pituitary gland responds by secreting hormones ...(100 of 170 words)

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