We measured carbon dioxide production and water efflux of 12 tippler pigeons (Columba spp.) during seven experimental flights using the doubly labeled water (DLW) method. Prior to the experiment birds were randomly assigned to one of two groups. One group flew as controls (no load or harness) on all seven flights. The other group wore a harness on two flights, a dorsal load/harness package (weighing about 5% of a bird's mass) on two flights, and they were without a load in three flights. Flight duration of pigeons with only a harness and with a dorsal load/harness package was 21 and 26% less, respectively, than the controls. Pigeons wearing a harness, or wearing a dorsal load/harness package lost water 50-90%, and 57-100% faster, respectively, than control pigeons. The mean CO2 production of pigeons wearing a harness or a load/harness package was not significantly different than pigeons without a harness or load. The small sample sizes and large variability in DLW measuremets precluded a good test of the energetic cost of flying with a harness and dorsal load.