Tens of thousands of snow geese flying at sunrise in the US state of Pennsylvania. The morning red sky created a grand backdrop for the geese on their annual migration. /VCG Photo

Photographer Guizhen Luo, 51, from Philadelphia, is a biologist who traveled to the 6,000-acre Middle Creek Wildlife Management Area in Pennsylvania to witness the migration. /VCG Photo

Ms Luo said the sunrise was particularly red and beauteous in the early morning because of a storm the night before. /VCG Photo