Plants that survive in anestuarine are calledhydrophytes, because theylive in water. The fourtypes of cord grass, whichis the most prominentvegetation in most estuarinewetlands, are smooth, common, dense- floweredand marsh-hay.
The mangrove isa small tree or shrubwith a grey twistedtrunk, leathery oliveleaves and tiny yellowflowers.
Glasswort, anative herb of thewetland, is namedfor the breaking-glasssound it makes when stepped on.
Beyond saltmarsh, wherethe land becomesdrier, turf-formingplants are favouredand a salt meadow develops.
The estuary is ahostile environment formost plants because saltdominates. A few growfurther back on theshore, where they livein a fluctuating environment of seawater and fresh water.
Small and darkgreen, with ribbon-like leaves, this planttakes root in sandysilts on tidal flats throughout thecountry.
Salt marsh areasare found at thehead of estuaries,landward of the seagrass and mangrove.
The great blueheron must live bya marsh watersource, where itnests among thegrass and bushes.
The broad-winghawk, common towetlands, percheson the bushes andwatches for prey.Unlike other raptors, this hawkmigrates in flocks.
The muskrat isideally suited forwet environmentsand prefersmarshes because of theconstant water level.
Known as mud wormsor bristle worms, thesesmall segmented creaturesare related to earthworms,but are characterized by a pair ofshort bristly structures on eachsegment.
The cockle ortuangi is ashallow-burrowingshellfish, foundfrom subtidal to mid-tide levels. Itis not related to the northernhemisphere cockle,
Three kinds of crab arecommonly encountered ontidal mudflats: Kairau, the tunnellingmud crab dominates theupper tidal zone. The mid-low tide zone is the realm of anothertunnelling crab – the stalk-eyed mud crab. The hairy handed crab is found throughout theintertidal zone.
Sand flounder Common sole In New Zealand at least 30 typesof fish use estuaries at significant Snappertimes in their life. Some, such assand flounder, yellow-bellied flounder,common sole, kahawai, grey mullet and yellow-eyed mullet, move in and out of estuaries eachday. Others – snapper, red cod and gurnard – areseasonal visitors.
Adult whitebait orcome down rivers tolay their eggs amongthe plants of theupper estuaries in latesummer and autumn, andthen die.
Waybills Caspiantern Tidal flats hold a bounty of foodfor wading birds, which gatherthere in large numbers to feed; forindividuals, there is littleprotection on the exposed flats.