The truth is out there:
“To investigate the flight dynamics and energetics of migratory bar-headed geese, we used custom-designed implantable instruments to measure abdominal temperature and pressure (every 30 s), tri-axial acceleration (100 Hz in 18-s bursts every 2 min), and electrocardiography (180 Hz in the same 18-s period) from seven birds, collecting data totaling 391 hours of migratory flight. The data loggers weighed 32 g and were housed in biocompatible tubing (dimensions 7 × 2 cm) capped by titanium electrodes.”
C.M. Bishop et al. The roller coaster flight strategy of bar-headed geese conserves energy during Himalayan migrations. Science. Vol. 347, January 16, 2015, p.250. doi: 10.1126/science.1258732.