Millions of hummingbirds travel across the continent annually and can make it difficult for us to decipher one from the other within the same species. Adult males, of course, have the obvious ruby colored throat that can appear black without light reflecting off of it, but the rest can look very similar. After watching generations of young appear in my yard over the years, I can tell you that the young males develop the gorget(throat feathers) very differently. They are probably the easiest to identify, however still difficult, unless you look at the throat markings. I have seen young males with virtually no dark gorget feathers, but will have one single glistening red dot appear somewhere on the throat. Then I've seen others with an obvious shadowed throat pattern(five o'clock shadow) indicating it's clearly a young male. The one imaged is one of the most advanced throats I've seen in my region. Being in the Northern most part of their territory it's uncommon to see red appearing on the young throats, but I have seen a small handful over the years. As they migrate south and mature, they develop their red patches and become far more obvious the further south they go. This, of course, only applies to the young males. The young females will remain dull in color for the sole purpose of protection and camouflage during nesting once they mature. The young Ruby-throated male hummingbird imaged is one of the most advanced throats I've seen in my region. Like I mentioned, I've seen a handful of birds with the random red spots, but this one is a consistent dark pattern throughout the entire throat. It was extremely easy to tell him apart from all the rest.
August 2017, N.E. of Edmonton, Alberta, Canada.