Holland Cotter explains how MoMA's new Sonnabend show is in part "a byproduct of legal hassles":
"[Rauschenberg's] 'Canyon' plays a major role here. The show revolves around it in a very
basic way. Because it incorporates the remains of a bald eagle, an
endangered species, the work could not be sold. When Sonnabend died and
her collection was appraised for tax purposes, her heirs ... valued the
unmarketable 'Canyon' at zero; the Internal Revenue Service, however,
estimated that it was worth $65 million and was prepared to tax the estate accordingly. A deal was struck. If the piece was donated to a museum, the estate tax
on it would be dropped. Both the Met and MoMA badly wanted it, and
Sonnabend’s heirs made conditions for a gift. The receiving institution would be required to mount an exhibition in
Sonnabend’s honor and inscribe her name in the museum’s list of founding
donors."
