RainLab.Blog Post List: List Sub-Categories under a specific Top-Level Category

I'm working on an October CMS project which use a blog where I need to seperate blog posts in two major categories. When listing blog posts using the RainLab.Blog plugin's Post List component, I need to list categories that are sub-categories under a specific top-level category and exclude other categories.

In the TWIG template, I want to iterate through and list out the categories that belong to "Birds" and not "Sealife".

In the default Post List component, categories are listed like this:

{% for category in post.categories %}
    <a href="{{ category.url }}">{{ category.name }}</a>{% if not loop.last %}, {% endif %}
{% endfor %}

I would like to change this to something like this:

{% for category in post.categories %}
    {# if category is a sub-category of "Birds"... #}
        <a href="{{ category.url }}">{{ category.name }}</a>{% if not loop.last %}, {% endif %}
    {# endif #}
{% endfor %}

So I would like the post to be listed as "Shorebirds" and "Hummingbirds" but not as "Corals" as this is a category that is not a direct child of "Birds".

I came across this stack overflow question, but it avoids rendering posts that do not match the criteria all together. I still want to fetch and render posts that are in other categories, but only list the categories if they match.

If it's totally fine to hardcode category then you can simply compare categories parent's slug or id to hardcoded value.

Here I am using the slug to compare parent, you can also use id it's totally up to you.

{% for category in post.categories %}
    {% set parentCat = category.getParent().first() %}                        
    {% if parentCat.slug == 'birds' %}
    <!-- here we are ^ comparing ^  please replace value as per your need -->
        <a href="{{ category.url }}">{{ category.name }}</a>
        {% if not loop.last %}, {% endif %}
    {% endif %}
{% endfor %}

now it should only show a categories which have a parent category having given slug.

if any doubt please comment