PUB00067 - Laserfiche WebLink

Home Browse Search

I . - ....... . '" "'-. -",... .~ '. .r.. ~'4l . '\. '. ~'" .~ ~'.:I.. ~~ ... ..~.f:.r ".~ ~. ~ -'it ""'.:- .:\-' " "\ .d .' !.' 'k... ~'l ;, _ 'c~_.'_" ,'; ,- '.~~ \'j - . . "" "? ' '. '\' --- ('(JfI/llIl/!/ f1J(/J:\h 1'/(JlIls: .l'lf/urfll'f'et! (1I'111i pink flulU-'!") IIlId If{/fefo"()/rf(Jol flIlO!o hy Ihl/iII ('OUpl'!: As the weather-and the water-continue to warm, shorebirds and ducks that breed in the area begin to arrive and feed on invertl'brates: mallards, pintails, green winged tl'al, Aml'rican avocl'ls, conHlOHl snip!" white-faced ibis, Virginia rails.... As the deeper waters warm and the marshes grow gn'en, American wigeon, gadwall and ntlH'r plant-eating birds coml' to brel'd and 10 fl'l'd on thl' nl'W Il'aves and shoots. The marsh wrens and blackbirds that nesl in bul- rushl's, cattails and other tall marsh plants feed themselves and their young on insects like mayflies and damsel flies. Snowy egrets and black- crowned night herons fl'l'd on fish and amphibians. EarI'd grebe and diving ducks like canvasbacks and redheads fl'ed on snails, insects and plants in areas of open water. The birds of the San Lois Valley have many ways of dealing with competition for food, which can be intense early in the season. Some species, like red-winged blackbirds, stake oul a territory and defend il against other members of their species. Other birds specialize in what they eat, the way they eat it or where they hunt for things to eal. For instance, ducks have filtering slructures called lumellue in their beaks. Shovelers have very small lamellae and feed on very small organ- isms. The lamellae of cinnamon teal are a little larger, and those of mal. iards larger still. Marsh systems like the San Luis Lakes do more than provide feed- ing grounds for migrating birds and nesting areas for birds that raise their young there. In mid- to late summer, mallards, gadwall and other ducks may travel hundreds of miles to the lakes and olher deep-water areas in order to moult and 10 feed on the high-protein foods that help them produce new fi>athers. Since these species shed all nf their flight feathers at once, Ihey must remain in the areas they chnose as moulting grounds until new fealh- ers mature and they can head snuth. As fall approaches and water levels are al their lowest, both adults and young birds raised in the area depend more and mnre on the valley's lakes, where they eat the seeds and tubers of marsh plants. Shorebirds on Iheir way snuth for the winter may linger to use Ihe mudflals created hy receding walers ,IS feeding grounds. Even when the lakes freeze over, Canada geese and snme mallards slay on, living on Ihe wannwater seeps thai are created around the valley's artesian springs-where water tem- peratures hover around 50 degrees Fahrenheit all winler. These birds will he first in line lor the abundance of the returning spring. Marshes like those found at San Luis Lakes are ve,y dynamic wetland systems. Their size and the depth of the water that covers them vary with the region's weather patterns and with the passlf/g seasons. .., y: "15 Ow/iI/I'd br (/ SOli Li/is .1/11/.1'('(, {f hell /fIullard dri(I\' Ii('/" Iril/J.:.I'. NO/II h.r Kel! ..\rrlll'r.