Select input in form not behaving as expected

I'm trying to set up a simple select input in a form but it's not working.

In my template I have the following:

<perch:input type="select" label="Select a preserve" id="preserve" options="Whaleboat,East Goslings,West Goslings" />

When I view the page containing the form I see the following in source:

<select id="form1_preserve" name="preserve"><option selected="selected" value=""></option></select>
    <option>Select a preserve</option>
    <option value="Whaleboat">Whaleboat</option>
    <option value="East Goslings">East Goslings</option>
    <option value="West Goslings">West Goslings</option>
</select>

It seems to be generating some seriously messed up html. Can anyone point out what I'm doing wrong?

Thanks, Tim