How to use Firebase authentication token to list user blogs using js

I'm trying to retrieve authenticated user blogs (granted scope):

var token = await firebase.auth().currentUser.getIdToken();

fetch('https://www.googleapis.com/blogger/v3/users/self/blogs', {
  "headers": {
    "Authorization": "Bearer " + token
  },
  "method" : "GET",
  "muteHttpExceptions": true
}).then( r => console.log(r) );

but i get error:

{
  "error": {
    "code": 401,
    "message": "Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
    "errors": [
      {
        "message": "Invalid Credentials",
        "domain": "global",
        "reason": "authError",
        "location": "Authorization",
        "locationType": "header"
      }
    ],
    "status": "UNAUTHENTICATED"
  }
}

Could you tell me please what I'm missing to achieve this without using back end ?