Field conditions may scientifically never be truly standardized because of perception constraints, logistic constraints or continuous dynamics in nature. The need to standardize experimental environments may depend on the scientific problems addressed or model systems considered. As an example, between-population variation in timing of reproduction in blue tits (a small European nest-box breeding bird) is sometimes larger in scientifically more standardized aviary conditions than in scientifically less standardized free-ranging conditions. Responses of blue tits to ‘artificial’ versus ‘semi-artificial’ conditions may result from scientifically ‘uncontrolled’ organism-environment interactions. Not all study populations may be preadapted to captivity and scientists most often don’t know this when they initiate laboratory experiments. Veterinarians may advise to use sterilized test cages minimizing infection. The practical problem is that blue tits will not breed in these highly artificial environments or that some populations cope better with captivity than other populations. Outdoor aviaries with ‘semi-controlled’ natural vegetation might be more appropriate for captive wildlife breeders, simply because they better simulate wildlife conditions. How can a veterinarian or members of ethical commissions that never worked with blue tits provide constructive advice about both scientifically and ethically acceptable experiments? Should ‘environmental sterility’ or the ‘mental state of captives’ been used to make decisions about how to conduct experiments? Do sanitary recommendations proposed by people not familiar with model species complicate execution of scientifically acceptable experiments that take background knowledge from model species into account? Sanitary conditions are never truly controlled in wildlife conditions anyway.