▁ ▁Mc Il hen ny ▁was ▁keen ▁to ▁study ▁the ▁birds ▁on ▁his ▁estate ▁and ▁began ▁bird ▁ring ing ▁in ▁ 1 9 1 2 , ▁initially ▁using ▁his ▁own ▁bands ▁made ▁of ▁tin ▁and ▁lead ▁on ▁du cks , ▁but ▁he ▁received ▁few ▁recover ies . ▁In ▁February ▁ 1 9 1 6 , ▁he ▁began ▁to ▁use ▁bands ▁issued ▁by ▁the ▁American ▁Bird ▁Band ing ▁Association . ▁Over ▁ 2 2 ▁years , ▁he ▁band ed ▁more ▁than ▁ 1 8 9 , 2 9 8 ▁birds . ▁Based ▁on ▁his ▁ring ing ▁studies ▁he ▁came ▁to ▁the ▁conclusion ▁that ▁sex - r ati os ▁in ▁du cks ▁were ▁ske wed ▁in ▁the ▁wild ▁with ▁males ▁surv iving ▁to ▁a ▁greater ▁age ▁than ▁females . ▁Later ▁studies ▁based ▁on ▁Mc Il hen ny ' s ▁ring ing ▁data ▁have ▁yield ed ▁considerable ▁information ▁on ▁the ▁movements ▁of ▁black ▁v ult ures . ▁ ▁In ▁ 1 9 4 1 , ▁he ▁wrote ▁on ▁the ▁potential ▁ext inction ▁of ▁the ▁iv ory - bil led ▁wood pe cker , ▁not ing ▁its ▁presence ▁in ▁his ▁estate ▁on ▁A very ▁Island ▁and ▁suggesting ▁that ▁the ▁destruction ▁of ▁old ▁growth ▁for ests ▁was ▁key ▁to ▁its ▁dem ise . ▁The ▁sub species ▁of ▁white - ta iled ▁de er ▁on ▁A very ▁Island ▁was ▁named ▁after ▁Mc Il hen ny ▁as ▁O doc o ile us ▁vir gin ian us ▁m cil hen ny i ▁by ▁Freder ic ▁W . ▁Miller ▁in ▁ 1