▁is ▁attached ▁to ▁the ▁bird ' s ▁leg , ▁has ▁a ▁unique ▁number , ▁and ▁a ▁contact ▁address . ▁The ▁bird ▁is ▁often ▁we ighed ▁and ▁measured , ▁exam ined ▁for ▁data ▁relevant ▁to ▁the ▁r inger ' s ▁project , ▁and ▁then ▁released . ▁The ▁rings ▁are ▁very ▁light , ▁and ▁are ▁designed ▁to ▁have ▁no ▁ad verse ▁effect ▁on ▁the ▁birds ▁– ▁indeed , ▁the ▁whole ▁basis ▁of ▁using ▁ring ing ▁to ▁gain ▁data ▁about ▁the ▁birds ▁is ▁that ▁ring ed ▁birds ▁should ▁behave ▁in ▁all ▁respect s ▁in ▁the ▁same ▁way ▁as ▁the ▁un ring ed ▁population . ▁The ▁birds ▁so ▁tag ged ▁can ▁then ▁be ▁identified ▁when ▁they ▁are ▁re - tra pped , ▁or ▁found ▁dead , ▁later . ▁ ▁When ▁a ▁ring ed ▁bird ▁is ▁found , ▁and ▁the ▁ring ▁number ▁read ▁and ▁reported ▁back ▁to ▁the ▁r inger ▁or ▁ring ing ▁authority , ▁this ▁is ▁term ed ▁a ▁ring ing ▁recovery ▁or ▁control . ▁The ▁find er ▁can ▁contact ▁the ▁address ▁on ▁the ▁ring , ▁give ▁the ▁unique ▁number , ▁and ▁be ▁told ▁the ▁known ▁history ▁of ▁the ▁bird ' s ▁movements . ▁Some ▁national ▁ring ing / band ing ▁authorities ▁also ▁accept ▁reports ▁by ▁phone ▁or ▁on ▁official ▁web ▁sites . ▁ ▁The ▁organ ising ▁body , ▁by ▁coll ating ▁many ▁such ▁reports , ▁can ▁then ▁determine ▁patterns ▁of ▁bird ▁movements ▁for ▁large ▁populations . ▁Non - ring ing / band ing ▁scient ists ▁can ▁also ▁obtain ▁data ▁for ▁use ▁in ▁bird - related ▁research