The delta of the Mississippi forms a natural ecological unit 

 with very precise boundaries. (This is not the area that 

 Mississippi valley folk call "the Delta," by which they mean the 

 bottomlands between the middle Mississippi and the Yazoo 

 rivers.) In some respects it is a southward extension of the 

 bottomlands of the Mississippi valley, with which it is connected 

 on the north via the narrow Atchafalaya Basin (between Natchez 

 and Baton Rouge). Whereas vegetation tends to grow in a 

 parklike manner on the limited drier areas in that basin, it does 

 not do so in the delta itself. In fact, the latter lies south of and 

 outside the Park Belt and is thus within the Prairie Belt; and. as 

 the land has dried out on the inland side, open grassfields have 

 come into existence there. The verges of waterways are lined 

 with gallery forest, and the extensive swamps are for the 

 most part covered with a closed-canopy swamp forest. 



The extensive open marshes bordering the coast are saline. 

 This small area, only 18,000 square miles in extent, is thus 

 a natural province. It forms a triangle 300 miles wide at the base 

 on the coast, about 100 miles deep at the apex, with northwestern 

 and northeastern sides of some 150 miles in length. To the 

 west it ends abruptly at the estuary of the Sabine River, beyond 

 which an entirely different kind of coastal prairie begins. 

 To the east it runs into the sea in the form of a 100-mile-long 

 peninsula lying almost parallel to the coast and ending in a very 

 strange topographical feature — a bird-foot-shaped minor 

 peninsula through the "leg" and "toes" of which the Mississippi 

 finds its way to the sea. North and east of this peninsula the 

 coast breaks up into hundreds of islands. The "leg" is 50 miles 

 long, and one of the "toes" is 21 miles long: it is estimated 

 the entire structure is growing at the rate of between 300 

 and 600 yards per year. 



The whole of this delta is sinking fairly rapidly due to what 

 is called isostatic adjustment, which means that the weight of 

 material deposited upon it is causing the underlying strata to be 

 compressed and also to sag. Thus, while the delta keeps growing 

 seaward, its main body is going down and also bending the 

 adjacent true coast line to the north downward. This is causing 

 the sea to flood in between the two on either side. As the 

 greatest deposits are on the east, the sag is greatest on that side, 

 and the sea has already flooded one hundred miles back west, 

 between the delta and the main coast. 



The whole delta is composed of old beaches and the filled-in 

 lagoons that once lay behind them. The main river channel 

 originally flowed southwest, but it has made four turns and now 

 points due east (see arrows on map). The coast is thus a series of 

 old river mouths, the position of which is identified by offshore 

 arcs of shallows (see numbers I to V on map). The major current 

 is the clockwise whorl of the Gulf, which pushes the whole delta 

 to the east, but there are wind-fostered, inshore, countercurrents 

 which cause beach material to move to the west. Offshore 

 reefs are caused by shell banks embedded in silt. 



The whole delta is a maze of lakes, rivers, canals, and 

 sloughs, locally called bayous. 



when it penetrates an almost saturated atmosphere. The ex- 

 ceedingly clean trees — for there was not one bit of dead branch 

 or trash anywhere to be seen — stood like cutouts with dark 

 trunks and billowing foliage above, while waving satin-gray 

 moss formed a succession of draperies everywhere. Beneath, in 

 unexpected but perfect contrast, the ground was carpeted with 

 foot-high, almost unbelievably green grass. Nor was this all; for, 

 growing in the grass, as if placed by the calculated hand of man, 

 was a sort of subforest of palmettos of quite another shade of 

 green and also all apparently without so much as a dead leaf. 

 Through all this the yellow sunlight poured in golden shafts. 

 Even more impressive was the silence. Not even the moss sighed 

 in the gentle wind; it just waved, and the shafts of sunlight 

 counterwaved. 



In addition to the raccoon that we had surprised grubbing for 

 his breakfast, less than ten minutes later we almost caught an 

 animal with the delightful scientific name of Myopotamiis coypu 

 (popular name, the Coypu), whose presence will be explained 

 later. We had also extracted an opossum from the base of a tree 

 and had roused a family party of deer. A flooded part of the 

 marsh was dotted at almost regular intervals with endless, small. 



low mounds of nature's debris, and, although it was such bril- 

 liant daylight, there were comings and goings among these, as 

 evinced by moving V's in the still waters. They were made by a 

 vast colony of the muskrats for which this whole province is 

 famous and from which furriers get the bulk of their raw mate- 

 rial. Later in the day we disturbed a pair of otters. 



There were wading birds standing about everywhere, in- 

 cluding large numbers of great blue herons. It was most en- 

 lightening here to be able to compare all the members of the 

 heron family at one time, for they were all there, even the great 

 white, which only in recent years has visited this locality from 

 its formerly very restricted territory in southern Florida. What is 

 more, a highly experienced bird-watcher who had brought us 

 specifically to see these herons was finally able to convince us 

 that both the white phase of the Reddish Egret and the white 

 immature of the Little Blue Heron (the adult of which is to my 

 eyes quite black) were also present. 



Even more interesting to me at the time was the extraordi- 

 nary number of very small birds that twittered and flitted about 

 between the palmettos and oaks and crept through the moss that 

 hung from the latter. That some were warblers 1 could see, but 



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