I cleaned my box out immediately after the first fledge. That was 3 weeks ago and they started to build again within the 3 week time frame so hopefully! The babies usually stick around all summer and sometimes help feeding the new clutch. Here’s hoping you get another! Do you have a Sparrow Spooker? I just had a very bad experience not putting mine up (lost an egg and now not sure if they will abandon :( )
