There are so many questions that are unanswered when it comes to hummingbirds, but the real fascination for me is how young hummingbirds instinctively know which direction to head for winter and why they even go into first place. Of course, we understand why they go south, but we're talking about a bird that has a brain the size of the peppercorn. We all know that they're spectacularly made, but do we really know the end of their abilities. Every year I witness young birds dancing around my garden and appear to be just randomly feeding without any direction. But when it's their time to go south, their territory expands from a small garden to thousands of square miles of unknown territory.
This picture appears to be blank, but the circles indicate two young Ruby-throated hummingbirds during migration. You may have to look at the images in full screen. I don't know if these were two of my locals or migrants from hundreds of miles north of me. All I know is that 1 minute one was feeding at one of my feeders and the other was at a distant feeder. When decided, one of the siblings lifted up into the air and gradually disappeared into the sky. The other followed shortly after. I'm absolutely certain that they have a communication system between them, but without apparently seeing the first one leave, the second one lifted off and eventually caught up with its sibling.
This is something I've witnessed repeatedly, and if I was to wage a guess, I'd say the younger sibling was still somewhat dependent on the older one. Ruby-throats typically migrate on their own, but in the case of two relatively young siblings, it's quite common for one to follow the other and eventually get separated during the southern migration.