Hummingbird Migration Through the Trans-Pecos Texas Flyway

Many species of hummingbirds fly or nest in the Trans-Pecos region of Texas between March and December. The movement of hummingbirds varies depending on the species, the time of year, and the stage of breeding, but many migrant hummingbirds fly up to 3,000 miles and migration journeys are often nonstop. We examined the timing and abundance of migration of various species of hummingbirds by conducting feeder watches. From April through the end of June, we observed three species of hummingbird visiting our feeders located on Sul Ross State University campus. The most prominent species was the black-chinned hummingbird, which were abundant during April and continued to visit the feeders through June. However, the male black-chinned numbers declined towards the end of June. This could be because the males had bred in this area and were continuing to migrate north while female black-chinned hummingbirds remained in the area to nest and raise their young. Female broad-tailed hummingbirds were observed visiting the feeders towards the end of June, and one calliope hummingbird was seen towards the end of June. Overall, we observed more females than males.

We also collected tail feathers from black-chinned hummingbirds to be used in stable isotope analyses to identify wintering sites. Stable isotopes are atoms of the same element that differ in the number of neutrons, and therefore differ in atomic weight.  Stable isotope ratios vary in different environments.  When hummingbirds eat, they acquire the stable isotopes of their surroundings, and these isotopes are stored in the bird’s tissue. Their feathers are considered a fixed tissue and when fully formed do not change chemically as the organism moves to a different location.  A hummingbird’s molting cycle occurs while at their wintering site, so the isotopes present in the collected tail feathers can be used to identify the location of the hummingbird’s molting and wintering site. More data will be gathered in the future as we continue this study.

feather

Tail feathers collected from black-chinned hummingbirds are used to determine where the birds migrating through the Trans-Pecos each summer spend their winter months.