Can you solve this Anglo-Saxon riddle

Ic wiht geseah in wera burgum,

seo þæt feoh fedeð. Hafað fela toþa;

nebb biþ hyre æt nytte, niþerweard gongeð,

hiþeð holdlice ond to ham tyhð,

wæþeð geond weallas, wyrte seceð;

aa heo þa findeð, þa þe fæt ne biþ;

læeð hio þa wlitigan, wyrtum fæste,

stille stondan on staþolwonger,

beorhte blican, blowan ond growan.

I saw a strange thing in men's strongholds

feeding cattle. Crammed with teeth,

it's useful beak is bent down;

it roams through plots, seeking plants,

raids them swiftly and returns home;

it always ferrets out the frail,

leaves the fine ones firmly rooted

standing still on their stalks

brightly blooming, glowing and growing.