Gatsby source filesystem name option

I have this import:

{
    resolve: `gatsby-source-filesystem`,
    options: {
        name: `Duck`,
        path: `${__dirname}/../static/content/collections/posts`
    }
}

I can see in Graphiql that it generates allDucks but, when queried, nothing comes through. When I query allMarkdownRemark though, I can see the posts.

How do I query with allDucks instead of allMarkdownRemark? Why is allDucks there anyway - if it's empty?