This year’s field season officially got underway with a week long workshop in southeastern Arizona. The purpose of the workshop was for the PIs of the hummingbird climate change project to select specific Arizona landscapes to be studied and to agree on questions to be addressed this coming summer. Additionally several interns from various parts of South America who will be working on the project this summer attended the workshop and were introduced to a variety of protocols for assessing nectar resources and measuring hummingbird energetics.
The Powers lab used this time to try out a revision of the non-invasive hummingbird doubly labeled water (DLW) protocol. The specific revision involves changing how we measure the initial dose size of isotopic water. To make this method totally non-invasive hummingbirds are dosed by feeding them nectar made with isotopically enriched water. Last summer dose size was calculated by weighing a syringe feeder before and after feeding the hummingbirds. This proved to be problematic as the syringe would occasionally drip creating large errors in our measured dose size. This year we have switched to measuring the bird before and after feeding. Additionally, we have purchased a more precise scale which should also improve the accuracy of our measurements.
The DLW sessions done during the workshop were highly successful! Between the two sessions (El Coronado Ranch and the Santa Rita Experimental Range) we labeled a total of 78 hummingbirds and recaptured 29. Our 37% recapture rate would be the envy of most doing DLW studies!