whiteclaw drowns in a battle
The title of the second book of the 4th series of Warriors is called Fading Echoes.
Silverstream.She died of giving birth to Graystripe's kits
Scourge dies in the 6th book of the Original Arc 'The Darkest Hour'.
In the Warriors series by Erin Hunter, Birdflight dies in the book "Bluestar's Prophecy". She succumbs to an illness and passes away peacefully.
In the book "Warriors: Sunrise" from the Warriors series by Erin Hunter, the character who dies is Bright Stream, who dies defending her kit, White Tail, from an attack by a shadowed figure.
In the book "Sunrise" of the Warriors series, Hollyleaf dies after being trapped in a tunnel collapse. She sacrifices herself to save Ivypool and Dovepaw.
When the leader of a clan dies in the Warriors book series, the deputy usually takes over as the new leader. The deputy is the cat chosen by the leader who is next in line to lead the clan.
It is called Moonrise.
If by ambush you mean the final battle then it is unknown because the book has not come out yet. It is rumored that Firestar dies but it is unknown.
Moonrise
So far, Stoneteller, from the tribe of rushing water, dies. That is all that I know so far, although I don't think he dies during the book, but before.
Sunset, book six of Warriors: The New Prophecy In other words, book 6 of the second series.