Feather development in songbirds

These are images taken over the course of an Eastern Bluebird nesting cycle. This should help to demonstrate the different growth phases that chicks undergo. All images are courtesy of Glen Williams. 

 

Note: NestWatch does not recommend that participants monitor a nest daily. Twice a week is sufficient. Also, though these images are specifically Eastern Bluebirds, most small song birds have a similar development pattern, although the nestling period may differ slightly.


 

Day 1 - Hatch Day - When the chicks hatch they are almost entirely bare. However, there are some spots of downy feathers, particularly on the head and along the back. However, their young status is still considered hatching young.


Day 2 - Though most bluebird chicks hatch in synchrony, it is not uncommon for one or two chicks to hatch a day late. The fourth chick is just beginning to hatch in this image.

Young status: Naked young (NY)


Day 3 - The young birds are still covered in down, although some feathers are starting to develop.

Young status: Naked young (NY)


Day 4 - The wings are now becoming dark as the future feathers develop just under the skin.

Young status: Naked young (NY)


Day 5 - Most songbirds can begin to open their eyes at about day 5. Feathers along the back, head and legs are starting to develop.

Young status: Naked young (NY)


Day 6 - At this stage, the feathers that cover the crural region, from the upper leg to the abdomen, are beginning to emerge.

Young status: Primary feathers in pin (PY)  


Day 7 - By this period, the nestlings are able to maintain their own body temperature. At this point, the female will cease to brood them during the day, but may continue in inclement weather.

Young status: Primary feathers in pin (PY)  


Day 8 - The secondary wing coverts are breaking out of the feather sheaths (their protective covering). The sheaths of the primary feathers have broken through the skin and are beginning to grow. These feathers are said to be "pin feathers".

Young status: Primary feathers in pin (PY)  


Day 9 - The capital feathers, secondaries, and rectrices (tail feathers) are out of their sheaths. The primaries continue to grow.

Young status: Primary feathers in pin (PY)  


Day 10 - The nestlings are now far more mobile. They have become able to crawl around the nest and they are able to stretch their wings out more effectively.

Young status: Primary feathers in pin (PY)  
 


Day 11 - The innermost primaries, all secondaries, and most capital-tract feathers have begun to emerge. Though their bodies are not completely feathered, after this point the nesting may be considered fully feathered for the sake of monitoring.

Young status: Primary feathers in pin (PY)  


Day 12 - The chicks are almost completely feathered by day 12, except for the midventral region (around the belly), which is feathered by day 13.

Young status: Fully feathered (FY)


Day 14 - The feathers have developed enough that the sex of the chicks can be assigned according to distribution of bright blue coloration on the primaries and rectrices, as well as the amount of white on the rectrices.

Young status: Fully feathered(FY)


Day 15 - The chicks are now completely feathered. They should be capable of weak, short-distance flights by this time.

Young status: Fully feathered(FY)


Day 16 - As the nestlings prepare for fledging, they huddle together, gape toward adults, preen, exercise their wings, stretch, move their wings, stand on the rim of the nest, look out of the nest cavity, and poke at grass in the nest.

Young status: Fully feathered(FY)


Day 17 - Though the chicks may not be fully grown they will reach adults size 2 to 3 weeks after fledging.

Young status: Fully feathered (FY)


Day 18 - Eastern Bluebird chicks fledge, on average, between 17 and 19 days. It is not uncommon for the younger chicks to stay in the nest an extra day. The adults slow the rate of feedings to try and entice the chicks out of the box.
This is an empty, flattened bluebird nest.
Young status: Young fledged from nest (YY)