, ▁after ▁being ▁re - int rodu ced ▁in ▁ 1 9 5 2 ▁by ▁a ▁Swedish ▁her ds man . ▁The ▁her d ▁is ▁now ▁stable ▁at ▁around ▁ 1 5 0 ▁individuals , ▁some ▁born ▁in ▁Scotland ▁and ▁some ▁introduced ▁from ▁Sweden . ▁ ▁The ▁str ath s ▁and ▁gl ens ▁of ▁the ▁national ▁park ▁feature ▁a ▁type ▁of ▁ancient ▁wood land ▁known ▁as ▁the ▁C aled onian ▁forest . ▁The ▁exp anse ▁of ▁p ine wood ▁that ▁st ret ches ▁from ▁Glen ▁F esh ie ▁to ▁A bern eth y ▁forms ▁the ▁largest ▁single ▁area ▁of ▁this ▁habitat ▁remaining ▁in ▁Scotland , ▁and ▁the ▁park ▁as ▁a ▁whole ▁holds ▁more ▁than ▁half ▁the ▁surv iving ▁C aled onian ▁forest . ▁In ▁these ▁for ests ▁can ▁be ▁found ▁bird ▁species ▁such ▁cap erca ill ie , ▁black ▁gr ouse , ▁Scottish ▁cross b ill , ▁par rot ▁cross b ill ▁and ▁cr ested ▁tit . ▁ ▁The ▁entire ▁length ▁of ▁the ▁River ▁De e ▁is ▁defined ▁as ▁a ▁Special ▁Area ▁of ▁Conserv ation ▁( S AC ) ▁due ▁to ▁its ▁importance ▁for ▁sal mon , ▁ot ters ▁and ▁F resh water ▁p ear l ▁muss els , ▁and ▁the ▁Don ▁supports ▁fish ▁such ▁as ▁sal mon , ▁sea ▁tr out , ▁brown ▁tr out , ▁e els ▁and ▁lamp rey . ▁In ▁upper ▁Str ath spe y , ▁the ▁In sh ▁Marsh es ▁form ▁one ▁of ▁the ▁largest ▁areas ▁of ▁flo od plain ▁m ire ▁and ▁fen ▁veget ation ▁in ▁Scotland