Comparing avian diversity between perennial and ephemeral water sources located within a Chihuahuan Desert ecosystem

Background/Question/Methods

Water availability in the Chihuahuan Desert is highly variable and dependent on various physical factors. Indio Mountains Research Station (IMRS), located in southeastern Hudspeth County, Texas, contains one perennial water source (Squaw Spring) and at least sixteen man-made ephemeral “tanks” previously used for watering livestock. It was hypothesized that bird diversity would be greater near Squaw Spring due to a continuous water source, because of biotic resources available to both permanent and migrating species, rather than ephemeral tanks where water availability is inconsistent.

The goal of this project was to confirm whether bird diversity is higher near a permanent versus non-permanent water sources. The experimental design included a multi-seasonal bird survey near Squaw Spring and around four temporary filled livestock tanks by means of visual sightings of different species, backed by photographic evidence to assure accurate identification.

Results/Conclusions

Although we expected that species richness of birds would be higher at Squaw Spring, results indicated it was actually higher around ephemeral water tanks. Once summer monsoon rains began, livestock tanks and adjacent terrain erupted with plant and invertebrate life that seemed to attract different bird species, especially summer transients. While the number of different species near the water tanks increased dramatically during the rainy season, the number of species near Squaw Spring remained relatively constant. These results can be used to initiate additional investigations into why there is a disparity in diversity between permanent and ephemeral wetlands on IMRS. Follow-up studies can include detecting components that regulate spatial inconsistency in bird distribution, including: food accessibility, habitat partitioning, competition between permanent residents and migrating species (i.e., resident dominance), behavioral differences, life history strategies between generalist versus specialist species, and distance from a significant source of water (Rio Grande) for transients.