You are looking at the faces of two very adorable Olive-backed Sunbird nestlings. They are eagerly waiting for their parents to return with food.
I was lucky enough to have a chance to glimpse a pair of sunbirds raising their chicks for about an hour.
During the short period of time, both parents actively fed their chicks with insects and spiders. Because they are so small, it was difficult to see what they brought to the chicks until I started reviewing all the photos I snapped.
After interesting activity is after feeding the chick will dispel a fecal sac to the waiting parent. A fecal sac is a mucous membrane that is generally white or clear with a dark end. It encases the feces making it easier for the parent to dispose of it. In this instance, the Olive-backed Sunbird chick turns its butt to face the nest opening as a signal to its parent that it is ready to defecate. The parent will receive the fecal sac from the chick's vent and dispose of it.