The many goldfinches which visit our garden and feast on sunflower kernels consume very much more than any other small garden birds e.g blue, coal and great tits. Could it be because they have a higher metabolic rate and need more food?
(Pardon the Scottish Accent)
Not convinced goldfinches have a higher metabolic rate than other small bird species, but not an expert on bird feeding. What I would say though, is even if your perception is correct in that goldfinches do eat more per bird than other species (though I agree with others saying they're particularly messy so waste more in general), eating more from feeders doesn't necessarily mean they're eating more. Feeders are just one source of food. It's highly likely that seed specialists are having to rely more on feeders in mid & late Winter for a higher percentage of their calorie intake. There's also the point about calories per food item.......and some species are better foragers than others.... I'd be surprised if BTO could state with any confidence re metabolism of individual finch species versus others.....will await with interest.