ESSEX BIRD-MIGRATION. 139
purposes. As a result of ringing it has been proved that birds
sometimes nest in localities other than those which were natal.
This is described as abmigration. I use the word in a still wider
sense, i.e., to include other irregular movements, as, for example,
birds wintering in different localities from year to year. Five
ringed Rooks have been recovered and each represents a different
combination. Three suggest migration and two abmigration.
One of these Rooks was ringed in Hanover, Germany, and two