BRI graduate assistant Maya Ressler with fellow student Ryan Keeling recording field data at The Nature Conservancy’s Davis Mountains Preserve, where much of Maya’s research was conducted.

By Maya Ressler and Dr. Ryan S. Luna

This study uses models to examine two possible issues affecting Montezuma quail in the Davis Mountains of Jeff Davis County, West Texas. One model examines the effects of extreme climatic events on simulated Montezuma quail populations, while the other model examines the presence of feral pigs to estimate how their habitat overlaps with Montezuma quail habitat.

Montezuma quail are an elusive quail species inhabiting the piñon-juniper woodlands of the southwestern United States and much of Mexico. They are extremely difficult to trap and study; thus, there is little known about their ecology and population or demographic rates. The limited studies conducted on the Texas populations show that their restricted range and overall population declines are attributed to habitat degradation and overgrazing. Because there is such little information on this species, there are unstudied factors that could be affecting West Texas populations, such as the influence of extreme weather events and new invasive competitors, like feral pigs.

To better understand how feral pigs affect Montezuma quail populations, we investigated the overlap of Montezuma quail habitat and feral pig presence, which is indicated by feral pig rooting behavior, as well as tracks and scat. Through rooting, feral pigs disturb the soil. This potentially reduces plant cover, alters soil composition, causes nutrient loss and alters vegetation communities. This could reduce forage resources, in addition to the ground cover, that Montezuma quail utilize for nesting, temperature regulation, and predator avoidance. We recorded the presence of feral pigs in the Davis Mountains Preserve, owned by The Nature Conservancy, and then extrapolated their presence across the entire Davis Mountains range. We estimated a 51% overlap of predicted feral pig presence and predicted Montezuma quail habitat in the mapped region. Feral pig presence didn’t completely overlap with predicted Montezuma quail habitat, but the overlapped areas occurred in critical habitat for Montezuma quail. These are areas that Montezuma quail need when their populations are low and resources are scarce. This opens the door to question if feral pigs have a negative impact on Montezuma quail resources and habitats, a question that deserves more research.

Extreme climatic events may also take a toll on Montezuma quail populations. The Davis Mountains contain some of the most contiguous habitat for these birds in Texas, and their populations are significant there because they can be a source population for range expansion of the species under good conditions. However, these populations may be vulnerable to habitat loss and adverse climatic conditions. Extreme climatic events, such as droughts, extreme precipitation and temperatures, snowstorms, and extreme wildfires influence climate averages through time, affecting both flora and fauna. There are several anecdotal reports on the sudden apparent decline of Montezuma in Texas, New Mexico, and Arizona following extreme climatic events, such as high levels of overwinter precipitation or droughts. It’s important to better understand these climatic events as they can impact vulnerable populations, like Montezuma quail in West Texas. Our model used population simulations which indicated that Montezuma quail populations can rapidly decline if they are subjected to several years of negative climatic conditions. These simulations showed that several years of poor climatic conditions decreased survival and recruitment of the species, leading to higher chances of local extirpation.

These birds are assumed to be relatively robust to regular droughts and changes to their environment. However, Montezuma quail populations might be vulnerable to back-to-back extreme weather events, as well as more aggressive, generalist competitors, like feral pigs. These two sources could alter Montezuma quail habitat and change, or reduce, choice resources. More fine-scale research is required to better understand how Montezuma quail are affected by these components. Further research should investigate Montezuma quail demographics and population dynamics to provide a firm baseline understanding of the species, as well as long term data analysis on climatic fluctuations.