BROWNSVILLE, Texas (ValleyCentral) — Perhaps, you have noticed large kettles of vultures soaring over the Rio Grande Valley in recent weeks as their annual spring migration is peaking.

While some vultures reside year-round in South Texas, others pour through by the tens of thousands each spring.

Seeking out overnight roosts in old neighborhoods with tall trees, or gathering by the hundreds at Sabal Palm Sanctuary east of Brownsville, these sentinels of death might appear unsettling, but they provide an important role as avian sanitation engineers.

There are 23 species of vultures worldwide, and the Rio Grande Valley is home to two, the Black vulture and the slightly larger Turkey vulture that sports a distinctive red head.

Both species have featherless noggins that help them stay cleaner as they dine on their preferred diet of carrion.

They are winged vacuum cleaners of the planet helping keep our environment free from rotting carcasses and diseases they carry such as botulism and anthrax. Vultures have stomach acid strong enough to destroy lethal bacteria and digest bones.

Vultures gracefully ride thermals, and as these consummate scavengers soar they use their keen sense of smell to locate fresh carrion.

Turkey vultures are able to detect the aroma of a potential meal from over a mile away, while Black vultures compensate for less stellar olfactory senses by following Turkey vultures to dinner.

Often joining the vultures are caracaras. Caracaras are actually members of the falcon family, but they won’t hesitate to devour carrion.

Even though they are smaller than vultures, they make up for it with attitude and will dominate a fresh carcass.

While often misunderstood and described as ugly, these winged cleanup crews provide a vital service in helping keep our environment clean.