The phrase "migratory season" refers to a specific time of the year when animals travel from one place to another in search of food, warmer climate, or for breeding purposes. Full definition
During migratory season, the caged birds became restless and exhibited increased hopping and wing flapping. (scientificamerican.com)
Through such a domino effect, wild birds might be able to transport the virus for a little while, but Karesh thinks H5N1 could not survive longer than a single migratory season in the wild bird population. (discovermagazine.com)
Moore and colleagues decided to answer the question by putting seven captive Swainson's thrushes, which are normally active in the day but fly at night during migration, into a cage and providing artificial sunrises and sunsets to mimic the migratory season. (sciencemag.org)