RIO GRANDE VALLEY, Texas (ValleyCentral) — Soaring in at sunset, hundreds of Snow geese raucously descend on this South Texas wetland where they have been roosting for several months.

They won’t remain much longer at their ancestral wintering ground, as their numbers are already thinning with primordial urges beckoning them to distant Arctic breeding sites.

The strident calling of wild geese fills crisp morning air as ragged V formations pass overhead on their northbound journey.

Snow geese are among the first to wing it northward, and while they migrate in large flocks, Ruby-throated hummingbirds fly solo throughout their 2,000-mile odyssey.

As waterfowl begin departing southernmost Texas, the vanguard of neotropical migrants begin arriving. You may have already glimpsed a ruby-throated hummingbird, as a scattering of males trickles thru the Rio Grande Valley mid to late February with more arriving in March.

These intrepid solitary travelers have likely just flown 500 miles nonstop from the Yucatan across the Gulf of Mexico. While they may tarry briefly in the RGV to rest and refuel, they are focused on reaching prime breeding grounds and staking out territories as far north as Canada.

The miracle of migration is not fully understood, but changes in day length and genetic predisposition are thought to trigger migratory behavior.

Secrets of their amazing navigational skills are apparently a combination of several types of senses as they are able to determine compass direction from sun and stars, while also detecting earth’s magnetic field.

Banded hummingbirds have been documented faithfully returning to the same site year after year revealing landmarks are also of vital importance.

While wintering waterfowl are on the wane in southernmost Texas, their departure transitions with the arrival of millions of migrating songbirds lingering briefly in the RGV before continuing their miraculous migration northward.