Keeping the birds water from freezing is a good idea especially for those who are at work all day. I would definitely want to try this

Pros: this would be great for the northern climates

Cons: none

Living in Ohio, we get freezing weather non-stop during the winter months. This is the time that the birds need water the most, so I installed one of these heaters on my bird bath. Here it is freezing outside and they're playing in the water. Brrrr....

Pros: Keeps water from freezing

Cons: None

This works great to keep the birds around for a little longer when weather gets cold.

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[updated on 2008-01-20 22:59:04]:
this product works great in bird baths. I use it in fall and the birds loe it. early morning when the chill is in the air they seem to flock to it like a hot spring.

Pros: keeps birds happy

Cons: none