Of the various species of woodpeckers that visit the feeders in the garden, two of them are very similar. The downy woodpecker and the hairy woodpecker are different sizes. They both have vertical stripes on their body and the males have the red patch on their head. I’ve added 2 photos of the birds at the same feeder so that you can see the size difference. There bills are different as well. The hairy has a longer, sharper bill.
Here is the downy on the peanut feeder. I compare them by how much of the peanut feeder is covered by their body, rather like a ruler.
Here you can see the hairy woodpecker, which takes up most of the height of the feeder. You can also notice the sharper bill in this photo. There are a few other differences in colouring as well but for me the best way to distinguish them is by their size.