▁v ult ures ▁also ▁cannot ▁be ▁band ed ▁on ▁their ▁legs ▁because ▁they ▁ur inate ▁onto ▁their ▁legs , ▁causing ▁cor ros ion ▁of ▁the ▁bands ▁into ▁a ▁pow der y ▁ox ide ▁that ▁st icks ▁to ▁the ▁v ulture ' s ▁leg ▁and ▁inj ures ▁the ▁bird . ▁Di ppers ▁are ▁also ▁danger ously ▁hand ic apped ▁by ▁ring ing ▁because ▁the ▁rings ▁indu ce ▁drag ▁that ▁makes ▁it ▁extremely ▁difficult ▁for ▁them ▁to ▁catch ▁pre y ▁in ▁fast - flow ing ▁water . ▁ ▁Among ▁species ▁which ▁can ▁be ▁safely ▁ring ed , ▁there ▁are ▁major ▁limitations ▁among ▁nom adic ▁species ▁of ▁the ▁desert s ▁of ▁the ▁Eastern ▁Hem is phere ▁and ▁card uel ine ▁fin ches ▁of ▁the ▁ta iga . ▁The ▁highly ▁un predict able ▁movements ▁inher ent ▁in ▁these ▁species ' ▁l ifest yles ▁means ▁that ▁recovery ▁rates ▁are ▁extremely ▁low , ▁especially ▁given ▁generally ▁low ▁population ▁dens ities ▁within ▁their ▁habit ats . ▁ ▁Similar ▁schemes ▁ ▁Wing ▁tags ▁▁ ▁In ▁some ▁surve ys , ▁involving ▁larger ▁birds ▁such ▁as ▁e ag les , ▁bright ly ▁col oured ▁pl astic ▁tags ▁are ▁attached ▁to ▁birds ' ▁wing ▁fe athers . ▁Each ▁has ▁a ▁letter ▁or ▁letters , ▁and ▁the ▁combination ▁of ▁colour ▁and ▁letters ▁uniqu ely ▁ident ifies ▁the ▁bird . ▁These ▁can ▁then ▁be ▁read ▁in ▁the ▁field , ▁through ▁bin oc ular s , ▁meaning ▁that ▁there ▁is ▁no ▁need ▁to ▁re - t rap ▁the ▁birds . ▁Because ▁the ▁tags ▁are ▁attached ▁to ▁fe