along the lower Colorado River and the 

 Salton Sea (Jorgensen 1975). 



Ongoing monitoring of the 

 light-footed clapper rail populations in 

 southern California (Zembal and Massey 

 1981) suggests that populations within a 

 marsh can undergo dramatic changes from 

 year to year, with some wetlands 

 increasing in numbers of birds (e.g. Upper 

 Newport Bay) , while other populations have 

 been eliminated (e.g. Los Penasquitos 

 Lagoon) (Table 15). Overall, 1981 

 censuses revealed fewer birds than 1980, 

 and the authors attribute some of these 

 changes to the heavy storms which occurred 

 prior to the 1980 nesting season. 



Table 15. Census of the light-footed 



clapper rail in southern California (blank 



space = no census). From Zembal and 

 Massey 1981. 



Location 



Tijuana Estuary 

 South San Diego Bay 



Marine Reserve 

 Otay River Mouth 

 J Street Marsh 

 F Street Marsh 

 E Street Marsh 

 Sweetwater Marsh 

 Paradise Creek Marsh 

 San Diego River Marsh 

 Mission Bay Marsh 

 Los Penasquitos Lagoon 

 San Elijo Lagoon 

 Batiquitos Lagoon 

 Agua Hedionda Lagoon 

 Buena Vista Lagoon 

 Santa Margarita 

 Upper Newport Bay 

 Huntington Beach Strand 

 Bolsa Chica 

 Anaheim Bay 

 Mugu Lagoon 

 Carpinteria Marsh 

 Goleta Slough 



No. of pairs 

 1980 1981 



26 



31 



It is easy to visualize the value of 

 a cordgrass marsh for bird feeding and 

 cover because the invertebrate fauna is 

 abundant and the vegetation is tall and 

 dense. However, there is a major limiting 

 factor for nesting — namely, the fact that 

 high tides inundate the habitat year 

 round, and the canopy is both too short 

 and too flexible to allow nest 

 construction off the ground. The solution 

 to this dilemma is a platform nest, 

 complete with ramp, built of dead Spartina 

 stems, which can float tn situ with the 

 rising tide. Clapper rail nest rims were 

 15 to 20 cm above the ground at Tijuana 

 Estuary (Jorgensen 1975), 15 to 50 cm high 

 at Upper Newport Bay, and 18 to 55 cm high 

 at Anaheim Bay (Massey and Zembal 1979). 

 Tall Spartina stands are the preferred 

 nesting habitat and the surrounding grass 

 stems are bent over the nest to form a 

 canopy, perhaps to provide protection from 

 flying predators. Incubation nests in 

 middle and upper marsh habitats were found 

 to be constructed closer to the ground, 

 and sometimes without the gazebo-like 

 canopy (Jorgensen 1975). 



A second type of nest is often built 

 shortly after hatching occurs in the 

 nearby incubation nest. These brood nests 

 are much less complicated in structure, 

 sometimes consisting of floatable debris 

 from natural and urban origins. 

 Presumably, these are used for nocturnal 

 roosting to avoid tidal inundation. 



Nesting can occur from April to late 

 July; clutch sizes range from one to eight 

 (based on numbers of eggs found in nests 

 by Jorgensen 1975 and Massey and Zembal 

 1979). The average size of full clutches 

 was just over five eggs in all three study 

 areas. Renesting following nest failure 

 was recorded in both studies. Incubation 

 time appears to be at least three weeks 

 (Massey and Zembal 1979). The elaborate 

 nesting habits of light-footed clapper 

 rails appear to be essential for hatching 

 success, for even with the presumed 

 protection from inundation and predation, 

 some nests fail to produce any young. 

 Actual recruitment rates and causes of 

 mortality after hatching both require 

 further study. 



80 



