I just returned from a successful trip studying red knots in Mustang Island and Padre Island National Seashore with David Newstead of Coastal Bend Bays and Esturary Program. We were trapping and surveying shorebirds and recaught 5 red knots with geolocators we attached to the birds last fall and spring ( see more about the spring trip here and geolocators here). The knots there do an interesting dance between the shores of Padre Island, where they get the majority of their food and the back bay called Laguna Madre, where go to roost safely. The catastrophic rains of the last few weeks in TX changed all that and it wasn’t good for the knots.
The Luguna Madre is a mysterious body of water that is moved more by wind than by tide. This is almost unique. In most coastal areas, the area between the barrier islands and the mainland fill with open water or intertidal mud flat and salt marsh grasses like spartina or wiregrass. Tidal waters flood these areas twice a day supplying nutrients to teeming communities of invertebrates and the food chain that feeds upon them. Wind controls water in Laguna Madre much like tide influences most other inland bays. This is so because of the meager gulf tide (usually less than 2 foot from high to low tide) and the few gulf inlets connecting the Laguna to the Gulf. In effect the Laguna is a big basin where water might shift from one side to the other depending on strength and direction the wind. The water depth, which is generally very shallow, is more influenced by rain than Gulf tide heights.
Last week was an unusually condition where rain water, as much a 10 inches in a few days, flooded into the bay. The rain and the drainage off the surrounding high ground raised the water levels which flooded all the areas where knots and other shorebird could roost. It couldn’t happen at a worse time.
As usually it was a conflict between people and birds. Padre Island National seashore, the longest barrier island in the country, often hosts fishing tournaments. Two weeks ago it was a shark fishing tournament. This weekend it was the coast-wide Surfcats Tournament, made more attractive by the Columbus day weekend and glorious fall weather. We rode to nearly the 30 miles marker south of the National Seashore entrance and the beach was virtually packed from beginning to end. With the beaches filled with people and the Laguna filled with water the knots and other shorebirds didn’t have a chance.
Knots usually occur in groups of 30 or higher on the Seashore, but last weekend we could find no group larger than 10-15 birds and most were in groups of less than 5. Why? Because there was no stretch of beach more than a few hundred yards without people. Usually the knots would escape the mayhem by lifting off to the isolated flats of the Laguna Madre. As the weekend went on the Luguna water levels fell and eventually birds started flying over to get off the beach.
The big news though is the retrieval of the geolocators. They will give us the first ever view of the Texas knots migratory pathway from beginning to end. For the first time, we will know where they winter, breed and the pathway that gets them from one end to the other.