. The Canadian field-naturalist. 1969 ASDERSOX ET CaiXfKDiATED HyVSOCAKBOSS Df BiBDS lo: ^ -. - 0,6C - PPM DDE+TDE FiGUBE 4. Relationship benreen DDE — TDE and eggshell thickness in "V^Tiite Pelicans. as described in Figure 3, except that these points represent individual pools rather than colonies. P< DECXrSTSG POPLTLATIOXS. REPRODLCTBT SUCCESS. AXD SUBLETHAL EFFECTS OF CHLORINATED HTDRoc.\RBOvs. Cramp ct aL {1964) h\-pothesized that declines of raptors in Great Britain were due to "sub-lethal effects in reducing ; Their ranges of residue levels in f
. The Canadian field-naturalist. 1969 ASDERSOX ET CaiXfKDiATED HyVSOCAKBOSS Df BiBDS lo: ^ -. - 0,6C - PPM DDE+TDE FiGUBE 4. Relationship benreen DDE — TDE and eggshell thickness in "V^Tiite Pelicans. as described in Figure 3, except that these points represent individual pools rather than colonies. P< DECXrSTSG POPLTLATIOXS. REPRODLCTBT SUCCESS. AXD SUBLETHAL EFFECTS OF CHLORINATED HTDRoc.\RBOvs. Cramp ct aL {1964) h\-pothesized that declines of raptors in Great Britain were due to "sub-lethal effects in reducing ; Their ranges of residue levels in four raptors ^"ere from to ppm. Lockie and Ratclrtte ( 1964) repoixed in ^reat detail on Golden Eao-le {Aquila cbrysaetos) t^q, breakage in Scotland. Egg residues on die order of to ppm were detected. E^^ies with histories of to ppm diowed definite q^^ breakage, ^rhereas e\"ries with residues of or less bred successfullv or resulted in occasionally addled, but not broken eggs. A certain percentage of addled eggs ^vas considered normal, as usuallv these eas^les lay r^o eggs but raise ordv one voung. These authors concluded that toxic chemicals were to blame as alTecting behavior of adults. Lockie (196") later stressing Dieldrin residues alone stated: ". . the critical level at which behavior became upset as evidenced bv effsf-breakins^. was no higber than 1 ppm (part per million) of Dieldrin in the egg contents. Ho^«*ever. this is a verv rough figure since other chemicals, for example DDE (a membolite of DDT). BHC and Heptachlor were present in varying amoonts . ." \^"urster and A^'ingate (1968) associated residues of to ppm in the eggs of Bermuda Petrels (Fterodromj cahcm-) with their declining reproductive success. Raiclijie \ I96~i) reported on egg breakage in Brnih Pereoiines Filco peregrinus) and on residues associated with unsuccessful evries (1~.4 mean ppm CH residues) and e^-ries \^"ith imp
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