invalid use of @serial tag

The following messages were uncovered while investigating a bug in javadoc.
The messages themselves appear valid. They are all instances of the same kind of message.

open/src/java.desktop/share/classes/java/applet/Applet.java:111: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Button.java:487: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Checkbox.java:663: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/CheckboxMenuItem.java:478: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Choice.java:711: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Container.java:3726: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Font.java:1944: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/Label.java:169: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/MenuComponent.java:450: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/event/FocusEvent.java:389: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/event/KeyEvent.java:2009: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.
open/src/java.desktop/share/classes/java/awt/event/MouseEvent.java:1197: warning: Tag @serial cannot be used in method documentation. It can only be used in the following types of documentation: package, class/interface, field.