If your image maps are directing to the same page but you want to identify whats clicked you could use a query string appended to the href value.
notice I have changed the page to a PHP extension. (M_BC.php) And notice the ?id=map1 after the page is defined.
HTML Code:
<area shape="poly" coords="181,186,158,181,147,167,171,172,175" href="M_BC.php?id=map1" target="_self" alt="British Columbia">
What you can do here is on the M_BC.php page add...
PHP Code:
$id = $_GET['id'];
This catches the value from the id key value which in the example above would be map1
just use a condition to test the $id variable contents then construct your dropdown based on that result