Category dropdown is displaying extra text

I’ve put this code from the WordPress codex on my home page

Code:

<form action="<?php bloginfo('url'); ?>" method="get">
 <?php wp_dropdown_categories('hierarchical=1'); ?>
 <input type="submit" name="submit" value="Search" />

The code is simply meant to display all of the WordPress categories, but for some reason, in the dropdown, it is also displaying the word “map” after most of my category names in the drop down (despite the word ‘map’ not being part of the category name). You can see what I mean if you click on the drop down box on my site.

Any ideas what the issue is?