Figure 3.16. Black-crowned night herons. 

 Juveniles (right) have streaked plumage. 

 Mclntire collection, © 1986 by Zedler. 



Most of our understanding of how brackish 

 marsh vegetation relates to saline conditions 

 comes from studies at the San Diego River 

 marsh (20 km north of Tijuana Estuary). 

 There, 1980 floodflows were prolonged by 

 reservoir discharge, and intertidal marsh 

 soils were oligohaline (under 10 ppt) for 2- 

 3 months. Cattails and several other brackish 

 marsh species invaded and dominated the 

 intertidal zone. As has been shown 

 experimentally by Beare (1984, Beare and 

 Zedler 1986), the adult cattails readily 

 tolerate saline conditions. Some individuals in 

 experimental treatments survived a year in 

 45 ppt water; aboveground parts died, but 

 rhizomes were able to resprout when 

 freshwater was resupplied. Thus, the 

 limiting factors for invasion are seed 

 germination, which declines to near-zero at 

 20 ppt, and the period of time required for the 

 cattails to grow salt-tolerant rhizomes 

 (estimated to be 2 to 3 months). 



Figure 3.17. Black-necked stilts and 

 American avocets (foreground) wade and feed 

 in the open water of brackish habitats. 

 Mclntire collection, © 1986 by Zedler. 



Table 3.4. Species that Boland (1981) saw 

 feeding in the river and temporary pools at 

 Tijuana Estuary. Data are frequency, i.e., the 

 number of visits when a species was seen as a 

 % of the total number of visits to each habitat 

 (n=10 visits to the river and 8 visits to 

 pools). 



a Data for the two species were averaged. 



44 



