The Ecology of Tijuana Estuary, California: An Estuarine Profile

anlmal footprints, In the hardpan for nest scrapes County wetlands and for restoratlon of Los Cerritos
if there are patches of other substrate, such as Wetland, and the Nat~onal Audubon Society's plans
sand or small wrack, the birds will Create thetr own for restoratlon and enhancement of Ballona
scrapes on these. When the pannes are inundated, Wetland). Much of the presumed value of brackrsh
snowy plovers also use them as feeding areas marsh habitats comes from studies of Upper
{Whrte, pers comm 1
Newport Bay (Zembal and Massey 1981a), where
the State's largest population of light-footed
3.5 BRACKISH MARSH clapper rails persists Ra~ls use both brackish and
salt marsh habitats at Upper Newport Bay and at
Habitats that typically have reduced water San Elijo Lagoon, and the nont~dal brackish
sailnrties (between 05 and 30 PP~) are considered marshes are a likely refuge for the b~rds dur~ng
brackish or mlxohaline (Cowardln et al 1979) In high water the proximity of several
southern Callf~rnla. such habitats occur next to brackish marshes along the periphery of saline
sef?pagljS Or where rainfall or runoff 1s impounded marshes may condltlons for rails The
Evaporatior~ then Concentrates salts Water levels cause-effect reiatlonships need to be tested, not
fluctuate widely but irr@gulariy. Due differences just for rails, but for the vartety of brackish and
in salinity and water !eveis, the plants and XIlmals saline marsh species Furthermore, the reciprocal
of the salt marsh are generally not found here lnteractrons, e, the use of saline marshes by
lnslead, a community more charactenstic of the
region's freshwater marshes IS found (Figure 32)
brackish spec,es, need to be ,nvestlgated
Catta~ls ITypha domtngensrs) and bulrushes
(SCIS@E)W$ caltfornica) are the usual dominants
among the emergent species, while the submergent
It may well be that fresh and brack~sh marshes
functlon as a generai refuge for anrmals when the
ciltcklgrass
seasanally
(Ruppia manbrna) is
Red-wing biackblrds
abundant
(Age/alus
estuary has high water It has been assumed that
the Dairy Mart Road Ponds. ahout 5 km upstream
phornfceus) comnionly set up terrttories In the tail, of Tljuana Estuary, are used by estuarrne birds,
dense vagetation, and dragonflies (Qdonata because marly species are seen ln both localities
An~soptc~ra, Figt~re 32) are obv~ous insect These ponds occur In areas where gravel mlrlirlg
inhabrtants
has left large pits, the water Source IS both rtver
flow and ground water Black-crowned night
T~~~~~~ Estuary, areas of brackish marsh
herons (Nyct~corax 17yctrcorax Figure 331, blackappear
to have forrned art~frc~ally following
necked st~lts (N~mantopus mexrcanus), Amcrtcan
t7ydrnloglc and topograpftlc modificatrons yhe
avocets ~Recurv~rostrarncricana, Figure 34) and
1928 air photo (Ftgure, 9) indicates that natural
"gretS see 'Over Of this
brackish njarsh mgy have been present at t+.le
report) are Gonspicuous among these tree-i1ned
inland lagoon b@Iora a channel was dredged to
ponds
make tho area tidal Before 1900, the area would
have Supparted brackish marsh if sufficient Boland's (1981) study of shorebirds ~n T~juana
rainwater accurnulaled or ~f seepages were
present In the absence of continual brackish or
Estuary provides supporttve data for the concept
that ponds provlde alternative resting and feedtng
freshwater rnputs, the depresslor? would probably sites during high tides He cornpared bird use In
have been an arkall sink colonized by brackrsh the intertidal flats with that of the river and the
species duriilg wetter periods
inundated salt pannes at the southern end of the
estuary (Figure 3) Of the 21 shoreb~rd specres
Brackish marshes are 11ow found at thc south found at Tliuana Estuary, 10 used both the river
end of thc ~nland lagoon In an area fed by urban and pool habitats for feed~ng (Table 6) Nearby, tn
and n~rficfd runoff at the: abandoned grave/ pits, the blocked channel (an area that was once tidalf,
where ralnfall accumulates, and st the southern a Somewhat drfferent group of birds, ~ncludrng
crtcl of the estuary, where sewage spills from black-necked stilt, ~haiaropes, and w~llets were
Mexlco through Geat Canyon provide an CommQnly found feedln9 (Figure 351 Heavy use of
~nttrnzltterrt water source Thc braided channels of
Ihc Tijuana River support epharnera[ patches of
these nonttdal areas by waders, sandpipers, and
plovers shows that estuarrne shoreb~rds are not
brackish marsh, but their locatton [ongevlty restrrcted to rntertrdal habitats
relate to recent flooding arid to spills of sewage or
~rr~~ation water
Qn at ieast one occasron, brackish marsh
specres expanded into the estuary under nontrdal
'The function of these brackish hab~tals relative conditions Blnrtng the 1984 closure, red-wing
to the esiuar~ne ecosystem IS under debate biackbircls rnovea Into the iower salt marsh and set
Further north, there rs evidence that springs were up terrrtsries tn the cordgrass Their effect on
fr'eqtrent around the intertidal wetlands, and various native salt marsh brrds (e g , Belding's Savannah
rest0ratlOn plans have called far the ereatfan of sparrows and clapper rails) was not assessed, but
iarge areas of fresh-to-brack~sh marshes (e.g., rt should be before recatnmendat~ons are made to
State Coastal Conservancy plans for Orange add brackrsh marshes along the peripnery of
3 2