While eagles have always visited this area during their fall migration from Canada to New Mexico, it has only been since 1990 that large numbers have delayed at Hauser Lake.
(eagles; have visited; this area; T:during their fall migration from Canada to New Mexico; T:always) (it; has only been; T:since 1990; that large numbers have delayed at Hauser Lake) Context(it has only been,List([98, 114))):(large numbers; have delayed; L:at Hauser Lake)
it has only been,List([98, 114))
eagles it large numbers
have visited has only been have delayed
this area T:during their fall migration from Canada to New Mexico T:always
T:since 1990 that large numbers have delayed at Hauser Lake
L:at Hauser Lake