Many of these birds occur in large numbers on east coast estuaries during their autumn migration from arctic and sub-arctic breeding grounds to wintering areas in South America.
(Many of these birds; occur; L:in large numbers on east coast estuaries; T:during their autumn migration from arctic and sub-arctic breeding grounds to wintering areas in South America)
Many of these birds
occur
L:in large numbers on east coast estuaries T:during their autumn migration from arctic and sub-arctic breeding grounds to wintering areas in South America