In honor of the official “First Day of Fall” on Saturday, September 22, let’s fall into seasonal changes in wetlands! When many people think of the transition from summer to autumn, the first thing that pops into their heads is leaves changing colors and seeing more sweaters and long pants. A less common thought is how wetlands change in the later months of the year. From species composition to hydrology, many wetlands undergo radical changes when summer turns into fall. Wetlands in coastal Louisiana are no exception.
For a start, seasonal changes can be observed with migratory species. Many species of birds and some fish and crustaceans use our swamps, estuaries, and other wetlands for breeding habitat in the summer months because of the abundance of food and warmth. On the other hand, some migratory birds like the famous Bald Eagle use the Mississippi River Delta as a wintering ground.  Blue Crabs, another species found in wetlands, mate around this time of year before going dormant for the winter.  Migratory birds are starting to migrate back to the southern hemisphere around this time to follow food resources.
Decreasing temperatures and humidity also cause plant communities to change. Wetlands experience loss of vegetation from wilting and freezes.  Black Mangrove distribution is limited by minimum winter temperatures. You can read more on mangroves and freezing here. Swamps and marshes lose much of their greenery with lower temperatures, which really decreases their water storage potential. Evapotranspiration, or water vapor leaving plants through their leaves, often decreases too, which means that water is not being cycled as quickly as at other times of the year.
Ecosystems in a stable state can weather the changes between seasons and bounce right back to full productivity in their peak season, but sometimes a large disturbance or even small, incremental changes over time can degrade habitat to the point of no return. Degraded wetlands provide less storm buffer, which is a crucial ecosystem service that protects us during hurricanes. It is in our best interests to preserve our wetlands through projects like CWPPRA because they are so critical and invaluable to us.
Featured Image from https://www.hcn.org/articles/the-disappearing-wetlands-in-californias-central-valley
As April passes into May, many migratory birds leave the tropics of Central and South America in search of bountiful summer resources in the sub-tropical United States. Among them, the very charismatic Prothonotary Warbler flies from the northern tropics to the hospitable habitats of the United States. Prothonotary warblers live in forests near bodies of slow-moving water where they can hunt for insects and nest in cavities in trees. The cypress swamps of Louisiana are about as good as it gets for a prothonotary warbler, and they stay from April to August.  If you get out into the swamp during the summer, look for their bright yellow figures darting through low-lying foliage.
Prothonotary warblers have experienced a population decline in recent years that experts attributed to the destruction of their wintering habitat in the tropics. To improve breeding success and survivorship, the Audubon Society and other ornithological enthusiasts have encouraged people to install nest boxes that help to protect warbler nests from failing. Many natural threats exist in swamps for warblers, including a variety of snakes, birds of prey, and mammals. Since brown-headed cowbirds will use prothonotary nests to lay their eggs in when given the chance, nest boxes are suggested to have a 1¼“ hole to prevent larger birds from entering the box but still allow the warblers to enter. Boxes are not left on the ground, and are often mounted on poles. Some predators can climb, so many boxes have a skirt/collar that prevents snakes, raccoons, and cats from climbing the poles into the nests. More guidelines for a good nest box can be found at https://nestwatch.org/learn/all-about-birdhouses/features-of-a-good-birdhouse/.
 Petit, L. J. (1999). Prothonotary Warbler (Protonotaria citrea), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.408
 Kaufman, Kenn. “Prothonotary Warbler.” Audubon, National Audubon Society, 10 Mar. 2016, http://www.audubon.org/field-guide/bird/prothonotary-warbler.
Brannon, Peter. “Adult Male.” All About Birds, The Cornell Lab of Ornithology, Florida, 14 Sept. 2016, http://www.allaboutbirds.org/guide/Prothonotary_Warbler/id.
Known to be one of the most easily recognizable species of waterfowl, the mallard duck is majestic, distinctive, and a wintering resident of the bayou state. The mallard is one of the most common ducks in the United States. With great variation between the two mallard genders, drake or male mallards have a bright yellow bill, prominent emerald green head, and white neck-ring, followed by a chestnut colored chest and dark colored rear. The hen or female mallards have a dark colored bill and are a mottled brown color with a dark brown stripe across the eye. Both drake and hen mallards have the characteristic violet-blue speculum with black and white borders. Mallard ducks are a migrating waterfowl species that can be found in Louisiana during winter. Among the dabbling ducks, mallards are one of the latest fall migrants with one of the most extended migration periods, lasting from late summer to early winter. During their migrant stay, mallards are found in agricultural fields, shallow marshes, oak-dominated forested wetlands, and coastal inlets with aquatic vegetation. Louisiana sits in the Mississippi Flyway, North America’s greatest and most heavily-used migration corridor. Louisiana’s coastal wetlands provide habitat for more than 5 million migratory waterfowl, approximately half of the wintering duck population of the Mississippi Flyway. Now, more than ever, restoration and protection of coastal wetlands is critical; if wetlands continue to diminish, Louisiana will no longer be known as “sportsman’s paradise”.