Side angle view
Of all the species in the
psittacine genus Amazona, the
puertorican parrot, Amazona vittata
is the least colorful.¹ Aside from a
limited amount of red in the forehead, and the white skin patches around the
eye, the rest of the body is covered with green feathers. On a perching PR parrot there is little color
besides green to be seen, the turquoise and black of the wings, the blue, red
and yellow areas on the tail are all kept well hidden. The reason for such lack of color is probably
the need to be as cryptic as possible to avoid attracting the attention of
predators.
The PR parrot brightest colors
are in the forehead and in the tail feathers.
The red band in the forehead
varies widely in width, length and shape.
Generally males have a wider red band than females, but not always. Perhaps the best example of the variability
of the forehead color in the species is the pair of PR parrots currently on
exhibition on the Juan A. Rivero Zoo at Mayaguez. The male has a single tiny
red feather in his forehead, the female has a red band wider and larger than
almost all females, so one on first sight could easily be fooled into thinking
she is the male and vise versa.
Very few people are familiar with
the color in the tail feathers of the PR parrots. The reason is that because they can only be
sighted when the parrots fan their tails, a normally brief occurrence, they are
essentially invisible to the casual observer.
But even if an observer happened to be at the
right place and time to see a bird with its tail fanned, from a distance the
colors are barely visible and unremarkable when compared even with even
modestly colorful species, such as the hispaniolan amazon (Amazona ventralis).
In the aviary the birds interact
in many ways during the day. Some of
these interactions involve body language, on occasions this includes tail
fanning which is normally accompanied by vocalizations and sometimes bowing and
wing cupping. The birds can do these
displays as parts of being aggressive and also for other reasons which are not
necessarily so easy to discern. Except
when we are selecting breeding pairs from the flock, or are concerned about a
bird being bullied, we don’t pay much attention to these displays.
About a decade ago, when I was
standing next to her breeding cage, a female known as Ann, did a bowing and
tail fanning display standing in front of me on the wire floor of the cage, very close to my face, this is, to this day,
an uncommon event (by the way, Ann and her mate, Pepe, used to be among the
tamest and sweetest birds in the aviary, but as they grew older they became
more and more intolerant of people around their breeding cage, now as they are
getting close to the two decade mark in their lives, when breeding, they are
hideously aggressive and among the most fierce of our pairs, but I digress).
When this event happened, it was
morning and sunlight was coming from my back and hitting the parrot head on. When Ann did her display, for a brief moment,
her green color became brighter the way a mirror becomes brighter when the sun
hits it at just the right angle. I was
intrigued by this but given that I had many other concerns at the time, filed
it in the back of my mind for future reference.
Early this year I found some a shed tail feather and decided to
photograph it to record how light reflected from it.
The feathers that are the last
ones at the sides of the tail are different from the other tail feather and any
other feather. They are asymmetrical and
one of their sides is blue. I found that
the blue of these feathers changes in brightness and you look at it from
different perspectives. If you look at
the feather from an angle of 90 degrees from top looking down at the top side,
the color is not particularly bright. But
as one changes the perspective, the blue becomes brighter and brighter as one
approaches the horizontal plane. If one
looks at the feather in the orientation that it would have if a parrot was
displaying standing in front of you the blue becomes almost mirror-like in its
brightness. You can see how the blue
changes in the photos.
What is the meaning of this
change of color? The birds have a
different color perception system than us, with four receptor cell types. Personally, I don’t know how the eyes the
parrot’s perceives the changes in color that my mammal brain reports to me. My own guess would be that if the feathers
undergo changes in color and brightness as a result of the birds fanning and
bowing, it may be that those changes play a role in courting displays,
alternatively it also could be important in aggressive interactions. It has
been shown that budgerigar females favor males whose face feathers display fluorescence.² For the moment, from a strictly scientific
point of view, I can’t say with any certainty what the brightness changes means
for the parrots. For all I know it
could be an artifact of perspective or of my own perception. Nevertheless I find it an intriguing
phenomenon. I don’t foresee the program exploring this matter as we have worked
hard to keep our birds from getting imprinted with humans and breeding pairs
are not fond of either people or photographic cameras.
¹Low, R. 1984. Endangered parrots
Ultraviolet vision, fluorescence and mate choice in a parrot, the
budgerigar Melopsittacus undulatus.
