Sunday, July 15, 2007

Prothonotary warblers

It's been 3 months since the woods have seen any appreciable rain. When storms clobber the rest of the county, the woods stay dry. Most of the swamp is dry now, making the turtle project a serious challenge while making vegetative studies a cinch. The absence of water means the absence of hovering dragonflies and invertebrates of duckweed mats. The dry part of the swamp is quiet now, too. The loud, consistent "Tsweet, Tsweet, Tsweet, Tsweet!" of prothonotary warblers can only be heard, occasionally now, in the deep swamp where water levels have dropped to a mere 3 feet in a month. Aside from their water source drying up, I think a few have gone south to their wintering grounds already.

Once appropriately called the "golden swamp warbler," the bright yellow and dull grey songbird was renamed by a handful of Creoles from South Louisiana. The warbler's colors connoted the vestments of a prothonotarius, a high-ranking papal assistant. The prothontary warbler was classified as a waterthrush for many years, but was eventually given its own genus, Prothonotaria. Like Lucy's warbler, the prothonotary warbler nests in cavities. Found along streams, rivers, swamps and sloughs in the eastern U.S. in small numbers, high numbers of breeding pairs live in the swamps of the southeast U.S. Go here to see a day-by-day photo log of the interior of a prothonotary warbler nest.

Abandoned downy woodpecker cavities are the preferred nesting sites, but prothonotary warblers will also use natural tree cavities, the broken tops of cypress knees, and even nest boxes. When natural nest sites are unavailable, they have been known to occasionally use open nests of red winged blackbirds. They don't just require cavities for nesting, they also require proximity to water. It has been suggested that nest sites over water are less prone to predation. Water introduces other dangers to nesting birds: if the nest is too low in the tree, it can flood. Fledglings can fall into the water and become a turtle's meal, though some suggest that fledgling prothonotary warblers have the ability to swim.

The loss of wetlands and hardwood forests have caused prothonotary warbler populations to decline at a rate of 1.6% annually since 1966. In the Mississippi Alluvial Valley, where breeding populations are dense, steeper declines have been recorded by the annual Breeding Bird Survey. Because the birds don't nest in the shrub layer like other warblers, early successional regrowth isn't sufficient for breeding populations. In the southeast U.S., only about 10% of bottomland hardwood forests remain, mostly in small, disjunct patches. The Audubon Society has authored a Bird Conservation Plan, which calls for the reforestation of 1,500,000 hectares of bottomland hardwood forest in the MAV. The reforestation tracts will join all of the small patches into one continous tract. Prothonotary warblers are one of the targeted species that one, large, uninterrupted forest will help.

Unfortunately, regardless of conservation efforts in America, the logging and drainage of wetlands (epecially the mangroves in Panama) in the Central and South American wintering grounds is seriously impacting the population. Several nonprofit groups, including the Missouri Bird Conservation Initiative, are working directly with industry, governments and private landowners in Central and South America to help conserve and protect the wintering grounds for roughly 62% of North America's songbirds, including the prothonotary warbler.

The prothonotary's bright yellow plumage is easy to see in a swamp, but most people don't spend time in swamps or other backwater areas where the birds live. Alger Hiss apparently did. From the Smithsonian Institute:
The sight of a Prothonotary Warbler along the Potomac River once made a birdwatcher named Alger Hiss so excited that he told a friend about his experience. Unfortunately, the fact that Whittaker Chambers knew about the prothonotary sighting was one of the links that a freshman congressman named Richard Nixon used to prove that the two men knew each other, leading to the conviction of Hiss (a suspected spy) on a perjury charge.
You might say that Nixon had the Prothonotary Warbler to thank for his subsequent rise to the Presidency!

No comments: