I report every bird that enters my loft , I also collect NEHU and Shu strays up and liberate them 86 miles away once a month . BOPS are the biggest problem , poorly trained young birds are the next problem and thirdly too much crap being sent if young birds are singled up prior to racing then they have to use there own brains / instincts to get themselves home the biggest loss are the ones that follow other birds rather than use there own brains . I believe a lot of culls are carried to boost numbers and breeding from more birds to get numbers so are all of a same age rather than breed 2 or 3 rounds from your best birds , fanciers should rely more on quality than quantity , less is more , and birds that aren't propped up by the medicine cabinet will fair better long term . Also forgot to add a lot of young birds go down in corn fields and can take a long while until there harvested and come out