January 2021

by Sarah Hood and Dillon Jones, San Diego State University Graduate Students

If you visited San Diego Botanic Garden this winter, you may have noticed some hummingbird feeders showing up among the plants. These feeders were a key part of a research project on Allen’s Hummingbirds that live in the Garden.

Sarah Hood, a master’s student at San Diego State University, is investigating the genetic make-up of populations of Allen’s Hummingbirds in Southern California to understand the behavioral science behind their migrations. This particular species of hummingbird contains two subspecies – one subspecies migrates to Mexico in the winter, while the other subspecies stays in SoCal year-round.

By catching hummingbirds in the winter – while the migrant birds are in Mexico – and then again in the spring – when the migrant birds have returned North, Sarah aims to catch birds from both groups. Then, she can compare the DNA sequences of the two subspecies and find areas of their genetic code that might be responsible for their different behaviors.

As you can imagine, in order to catch a hummingbird, you must be very quick and precise. These birds are captured using a drop-down mesh trap arranged around a feeder – it acts a little bit like the falling cage from the game Mousetrap. When a bird goes under the trap to drink from the feeder, a researcher releases the trap using a string and it closes around the bird.

After capturing the hummer, Sarah collects the bird’s data. This includes taking its measurements, weighing it, keeping a few feathers for isotope analysis, and taking a genetic sample from its toenail. Then a small band is placed around one of the bird’s leg with an identification number, and its head is painted with non-toxic washable paint – to avoid recapturing the same bird twice. After getting a drink of sugar water for the road, the hummingbird is released back into the wild. The entire process takes about 15-30 minutes.

If you are interested in learning more about Sarah’s research, please contact her at shood@sdsu.edu.