Newly-fledged Robins show off their final downy feathers on their heads. The juvenile on the left has longer tail feathers than its younger sibling, so it hatched first. (Note cards available here.)
Behind the lens
Birds that leave the nest right away ("precocial") tend to all hatch within hours of each other. Birds that are fed in the nest for a while ("altricial"), like Robins, tend to hatch over a longer period of time. This way, the number of altricial chicks that survive is dependent on how much food the parents can deliver. The late-hatchers are smaller and less aggressive than their siblings, and they only survive if there's plenty of food to go around.
Personally, I can relate to the altricial birds like these Robins -- I'm the youngest of seven sons, and I grew up pretty skinny!
birdRobinbaby birdGlacier National ParkMontanaAmerican RobinRobin Red BreastJohn Ashley