This is because there are generally fewer insects, larvae, caterpillars etc.The surveys birds with greater access to human feeding are probably in urban areas and the birds with no access to human feeding are probably in rural areas.So the disparity is almost certainly explained by the location and is not likely to be a detrimental affect of human feeding.Survival of the fittest implies unimpedd habitat, or time to adjust.We are killing birds at massive rates, with our glass buildings, deforestation and general disruption.The speed with which we destroy cannot be effectively offset by evolutionary changes, which take time.Feeding a few birds cant hurt them.I realize it tends to favour the seed eaters, but better them than no help at all.Making bird friendly habitat gardens helps too.And cutting back on pesticides.Birds being fed are of course much easier to observe and much more likely to continue to return to the same area each day.Certainly if times got tough I would expect almost all species of birds to move entirely or expand their foraging range unless they had a consistent feeder to take advantage of.Also, these feeders become concentrations points at which interactions and possible disease transmission can occur between species that do not typically come in contact.A choice of foods should be offered, in a variety of feeders, always with plenty of good nearby cover.The result should generally be greater health, greater survival during times when natural food supplies are scarce, better reproduction.I prefer to feed year round, without ever missing a day or letting the feeders get empty.There will always be undesirable outcomes.While feeding is unnatural, so is everything else weve done to nature.Feeding is small compensation to wildlife for the damage weve done to their environment.Feed the animals is good advice.I agree with comment that siding survival of less healthy birds shall produce statistics affected by inclusion of information skewed by their presence.I do not see this probable impact as absolutely a negative.More studies are needed before any conclusions can be drawn.One of the cited studies suggests that it is the quality of the provisioned food matters.When fat sources were supplemented with vitamin E, the negative effects on egg quality were mitigated.We emphasize, however, that our study focussed on egg phenotypes; it will be important to see how these effects translate into fitness consequences.The mechanism by which these negative effects were generated is of key importance; the provision of energy-rich fat supplements in winter had negative consequences for female egg investment several weeks after provisioning stopped.Yet at the population level, this was mitigated by the provision of fat together with vitamin E.This is the first direct evidence that the specific nutritional composition of provisioned foods may determine whether carry-over effects on breeding performance are positive or negative at the population level.Therefore, where provisioning is practiced as a conservation tool, careful consideration should be given to the nutritional composition of foods.Whether winter provisioning of garden bird species is considered to be beneficial or deleterious may depend on whether effects are interpreted at the level of individuals or populations.
Other
Bird feeding
Provide the necessary food and feeders for them and no one gets left out.
I have not seen an increase in the more aggressive birds versus the more timid ones, just separate them.
