How Painted Buntings grow and molt

The life cycle of a Painted Bunting is complex.  In the field, it is virtually impossible to tell if a green bird is a female or a young male.  So, maybe this will enlighten the situation.

A bunting is born in the "summer".  For the eastern birds this occurs in North Carolina, South Carolina, Georgia, or coastal northeast Florida.  At that time a young bird is greenish/brownish.

Painted Bunting (juvenal)
Photo courtesy of PBOT, UNC Wilmington

Not to confuse things but these birds actually do another supplemental molt and grow more green, somewhat older looking feathers.  This happens soon after they hatch so we don't see these changes.

Now these birds fly to Florida for the winter.  This is where we band them.  In nature, it is not possible (despite beliefs) to tell a young bird from a female.  Sometimes they look grayer but this is not reliable.  The feathers we use to age birds are hidden in a folded wing.

Painted Bunting - hatch year 

Unless you enlarge this photo it may be hard to see the differences.  If you look closely at the small feathers above the outer wing feathers (to the right of the thumb), you might see that the feathers are gray.  Also, the shafts of the flight feathers are darker on the outer 5 feathers and browner toward the inside.  This is the wing of a "green" born the past summer like the example we started with.

This bird spends the winter in Florida, flies north to the breeding grounds in the spring.  It is still green.  If it sings on territory, it is male.  There have been observations of a green male sucessfully nesting despite not yet having typical male colors.  (Not my observation but those of Dr Rotenberg, UNC Wilmington who does the counterpart breeding study to our over-wintering study.)

Now fall comes around again.  It has been 15 to 18 months since birth.  Molting starts.  A young female bird gets green feathers (see wing below).  A young green male gets blue and red feathers growing in.  For the most part, this is done on the breeding grounds although some Florida folks note some molting birds at their feeders in August.  This is typically at the end of that molting.  At this time the adults also molt.

Painted Bunting - male molting in its first male colors
Photo by David Simpson

In hand, a wing of an adult female looks different from the previous young wing:  The same feathers above the outer flight feathers now have a green edging and all of the flight feather shafts are shinier black.  This is the only way we can tell a female from a young green.  I encourage you to click on these photos to enlarge them.

wing of an adult female Painted Bunting

So, 15-18 months have passed and we now have adult Painted Buntings!

Painted Bunting (female - aged in hand)

Painted Bunting - male

There are many color variations in "typical" Painted Buntings.  Below is a collage of some of the variations we have seen.  There are many more.  It is not unusual to see these variations from green feathers among the red feathers of a male's belly, white (albino) feathers, a more bronze look, or different colored feathers.  There are also genetic variations that can happen.        

One of the variations seen frequently is a green bird with a very red cast to the belly.  I have been told that these are typically older females that develop more male hormones as they age.  This photo was sent to a panel of experts who agreed that this was an older female, not any other color variations or genetic changes.  We all have hormones of both sexes, just different quantities.  So do buntings.

Painted Bunting - older female

Another variation may occur when a bird loses a feather outside of molt time.  Hormone levels may be different at that time so any feather may grow in a different color.  This is why sometimes a green bird may have a few blue feathers on its head.  That bird could be a female!

1 comment:

  1. Hi Nancy - thanks for the wonderful explanation of the molt sequence of PABU. We caught 3 green buntings 2 weeks ago and I was fuzzy on if/how I could sex them. Now I know what to look for. Happy Banding!
    Jim McGinity