Less Annoying CRM has a filtering option to find contacts with a particular birthday. Start from the Find a Contact page, and find the Filters & Sorting options in the page menu on the left.  From there, select “Add a filter,” the bottom option.

Next, select “Birthday” in the dropdown list. Under Birthday there are a few different options to choose from, depending on how you would like to filter.  To search for birthdays in a particular month, select “is between” “August 1” and “August 31” (you don’t need to worry about the year here since a contact's birthday is the same date every year!).  

Once you have made the desired selection, hit Apply filter to see a list of contacts with birthdays in the date range you chose. That's it! You can use this list to view contacts with birthdays in the selected range, and you can even export this list using the link in the upper left.