def get_children(children, node_dict, child_list):
    """
    Recursive function that finds all species level taxa id's from a given
    taxa id.
    """
    for child in children:
        if child[1] != 'species':
            new_child = node_dict[child[0]]
            get_children(new_child, node_dict, child_list)
        else:
            child_list.append(child[0])

    return(child_list)