Ive come across geese at 14000ft during the day but I didn’t know birds flew at night.
During my Air Force career, I remember seeing flight safety traffic about a bird strike involving a turkey vulture that collided with an RF-4C from the Idaho Air National Guard. Impact shattered the windscreen and the birds’ remains squarely struck the pilot, leaving him seriously injured. The RF-4 was at 15,000 feet when it struck the vulture.
Fortunately, the RF-4C had dual controls and the WSO landed the jet from the back seat. The accident ended the pilot’s career.
Geese will definitely migrate in the dark.