Figure 58. Major duck migration 

 coast marshes (Bellrose 1980). 



corridors to gulf 



Bird populations sre largest during the 

 winter when ducks and geese are abundant. 

 It is misleading to group all these 

 species, however, as sone migrate on 

 through to South America, as shown for the 

 pintail and teals. These two species 

 reach peak abundance late in the year and 

 again in the spring, apparently because a 

 large proportion of the population moves 

 south across the gulf in mid-winter. 



Wading bird densities in the marsh 

 peak during the summer. Although they are 

 year-round residents, they appear to be 

 much more active in marshy areas during 



the summer (Mabie 1975). About 60 species 

 of land birds, mostly songbirds, migrate 

 through the delta to South America each 

 year. They do not use the marsh exten- 

 sively, but usually fly over it. However, 

 during northward spring migrations they 

 frequently encounter strong head winds and 

 take refuge on the first landing sites, 

 the cheniers and slightly elevated marsh 

 ridges. During these occasions their 

 densities can be very high, and the 

 marshes can be important for their sur- 

 vival. Some of these songbirds, like the 

 red-winged blackbird and the great-tailed 

 grackle, nest in the coastal marshes in 



82 



