▁between ▁November ▁and ▁April ▁each ▁winter . ▁The ▁temporary ▁lake ▁that ▁is ▁formed ▁by ▁the ▁flo oding , ▁similar ▁in ▁some ▁respect s ▁to ▁a ▁t url ough , ▁can ▁be ▁up ▁to ▁ ▁long , ▁up ▁to ▁ ▁in ▁extent , ▁and ▁up ▁to ▁ ▁deep . ▁ ▁This ▁type ▁of ▁habitat ▁is ▁now ▁very ▁rare ▁in ▁Wales . ▁▁ ▁The ▁wet land ▁was ▁identified ▁in ▁ 1 9 8 2 ▁as ▁a ▁site ▁of ▁regional ▁importance ▁for ▁a ▁variety ▁of ▁bird ▁species , ▁including ▁common ▁red sh ank , ▁northern ▁lap wing , ▁m ute ▁sw an , ▁common ▁re ed ▁b un ting , ▁western ▁yellow ▁w ag tail ▁and ▁common ▁sh el du ck , ▁all ▁of ▁which ▁are ▁bre eding ▁species , ▁as ▁well ▁as ▁accommod ating ▁winter ▁visitors ▁not ably ▁Bew ick ' s ▁sw an ▁and ▁E uras ian ▁w ige on . ▁▁ ▁The ▁site ▁also ▁contains ▁other ▁habit ats , ▁including ▁running ▁water , ▁marg inal ▁and ▁in und ation ▁veget ation , ▁that ▁contribute ▁to ▁its ▁wild life ▁interest . ▁ ▁In ▁the ▁summer , ▁surface ▁water ▁is ▁restricted ▁to ▁the ▁bro ok ▁itself . ▁ ▁Ge ology ▁and ▁hydro log y ▁So ils ▁on ▁the ▁site ▁compr ise ▁heavy ▁cl ay ▁with ▁some ▁pe at , ▁super im posed ▁on ▁gla cial ▁and ▁est u ar ine ▁gra vel ▁and ▁mud ▁depos its . ▁ ▁In ▁turn , ▁these ▁overlay ▁Tri ass ic ▁dol om it ic ▁con gl omer ate ▁in