The Principal Bird Deity

This is a censer stand from Guatemala 250 AD to 450 AD.
The face on it is the Principle Bird Deity's. From LACMA.

You can find it on the sarcophagus lid of Pakal, in the San Bartolo murals (on the West Wall) and other places. The Principal (or Principle) Bird Deity (or just the PBD) was a major god for a time in the ancient Maya civilization. Its heyday was the Preclassic Period and the Early Classic part of the Classic Period. The Maya connected this being with valuable things -- like jade -- as well as other things.

Features

Artists in the Classic Period tended to draw the Principal Bird Deity's face like this: its eyes (and its pupils) were square-shaped. Its face also has a "beak-snout." (Another description I came across says that the being has an upper lip that's long.) It was also popular to draw it with a beard that had jewels in it. (The Classic Period way of drawing this being's face is the same as the way that Classic Period Maya drew the face of a being called Ux Yop Huun -- also known as the Jester God. The ancient Maya saw a connection between these two beings, but archaeologists don't quite know what it was yet.)

Part of an image in the Met's

collection. The artifact dates 

to the 400s AD or to between 

350 AD and 550 AD. It has a two-

headed snake in its mouth. The 
two sources I found don't agree: only
one says it is the Principal Bird Deity.

As for its wings, sometimes the Maya drew things into them. One of these things was either snakes heads (from the side) or snake figures -- these are two separate descriptions, each from a different source. It may sound unusual to put snakes on wings, but the word for snake and sky are the same in Mayan writing, so it's possible that the snakes could actually represent the sky, in a way. Speaking of snakes, artists also liked to draw it having a snake in its mouth.

There are a number of important features that are related to its forehead and the top of its head. Its forehead has a mirror, and it may also have what's called an "ak'bal medallion." On top of its head, it may also have a shell ornament that's been carved -- it may have this and the medallion or just have either one. There are times where it wears a "ak'bal flower headdress," a headdress that Itzamná is commonly drawn wearing. 

There's a theory that this bird's appearance may have been based off of a real species of bird called the laughing falcon or guaco (Herpetotheres cachinnans.)

What It Was God Of

This jade figure (dated to the 200s AD to
500s AD) comes from Honduras is either of: 
a person impersonating the PBD, or a 
humanized version of the god. From the 
Metropolitan Museum of Art.

The ancient Maya thought of the Principal Bird Deity as connected with the valuable things that the earth had to offer -- two examples are quetzal feathers and either maize or maize fields (I've seen both mentioned.) 

However, the strongest connection the ancient Maya made with the Principal Bird Deity was jade: they thought it was a living version of the mineral. (Another valuable thing the ancient Maya connected with this being was water, including rain -- this was because the ancient Maya's connections with jade included water.)

Rulers

Another association this god had was with rulers. By connecting themselves with the god, rulers were connecting themselves with control of valuable items -- as well as control of the economy.

Detail from a rectangular, ceramic
box that comes from Guatemala
and dates to between 450 AD and
550 AD. From LACMA.

The Principal Bird Deity was one of the gods that rulers would impersonate with the intention of being possessed. The point was to talk with the Principal Bird Deity, to get it to do things for the people. (Speaking of rulers and the Principal Bird Deity, artifacts depicting this deity were popular as grave goods for rulers.) 

Rulers are also shown wearing a headdress made of the Principal Bird Deity. This headdress was worn as part of them taking the throne -- and was a tradition that lasted from the Preclassic Period to the Early Classic.

And, on a related note, from what's been seen of ancient Maya art, rulers liked to include quetzal feathers in their headdresses. Used this way, it's possible the feathers were meant to be a symbol of the Principal Bird Deity.

The Sun
The ancient Maya in the Preclassic Period tended to connect the Principal Bird Deity with the sun more so than the ancient Maya in the periods that came after. (There's also a view that says this only may been what happened.) 


Itzamná 
The ancient Maya thought the Principal Bird Deity was a form of Itzamná. (No one knows for sure if the connection between the Principal Bird Deity and Itzamná started in the Classic Period. There's an idea that wonders if the belief that it was a form of Itzamná replaced the belief that it was connected with the sun. ) 

Archaeologists have found evidence that there were times where the Principal Bird Deity delivered messages for Itzamná. The name for the Principal Bird Deity as a messenger could be Muut Itzamnaaj. This phrase means "Itzamnaaj Bird."

There are some artifacts that say the Principal Bird Deity's name is Itzam Yej. This name is seen as evidence that connects the Principal Bird Deity with Itzamná. 

There's a possibility that Itzamná (god D) is actually a mix of yet another god, Pauahtun (god N,) and the Principal Bird Deity.

Creation Story
Another myth about the Principal Bird Deity has him being punished, and that his punishment was part of what happened before the creation of people. The Tablet of the Cross (at the site of Palenque) has a version of this creation myth. The tablet says that Hun Ajaw, one of the Hero Twins, was the one who punished the Principal Bird Deity -- who was self-centered enough to think it was bright enough to be a sun. After it was punished it used the World Tree to get to the sky. After all this, the real sun was able to rise.

If you've read about the Popol Vuh, then you probably are reminded of Seven Macaw (Wuqub Kaqix or Vucub Caquix.) Sometimes you may come across descriptions of the Principal Bird Deity that say this god is Seven Macaw. However, there is also a view that these beings were not the same, on account of how much of time that had passed.

Consideration
The name Principal Bird Deity is also a term used for other bird beings. Not a lot is known about these beings.


References:
Google Books: "Art and Myth of the Ancient Maya"; Oswaldo Chinchilla Mazariegos"; 2017

Google Books: "The Origins of Maya States"; Loa P. Traxler, Robert J. Sharer (editors); 2016

Hampshire College: “Birds and Environmental Change in the Maya Area”; Peter Stuart; May 2015
(Automatically downloads  to your computer)

Google Books: "Maya Imagery, Architecture, and Activity: Space and Spatial Analysis in Art History"; Maline D. Werness-Rude, Kaylee R. Spencer (editors); 2015

LaGrange College: "Donning the Mask: Mayan Belief, Christianity and the Power of Syncretism"; Blakeley Coull; 2014

Leiden University: Leiden Repository "The Maya Ceramic Book of Creation: The Trials of the Popol Vuh Hero Twins Displayed on Classic Maya Polychrome Painted Pottery"; Laura Beukers; June 17, 2013

Mesoweb: Maya Archaeology Articles: "The Name of Paper: The Mythology of Crowning and Royal Nomenclature on Palenque’s Palace Tablet"; David Stuart; 2012

Google Books: "Spirit Possession and Exorcism: History, Psychology, and Neurobiology" volume 1 "Mental States and the Phenomenon of Possession"; Patrick McNamara; 2011

UC Riverside Electronic Theses and Dissertations: "A Study of Classic Maya Rulership"; Mark Alan Wright; January 1, 2011

MAYA VASE: "At the Court of Itzam Nah Yax Kokaj Mut: Preliminary Iconographic and Epigraphic Analysis of a Late Classic Vessel"; Erik Boot; October 30, 2008 

Google Books: "Ritual & Power in Stone: The Performance of Rulership in Mesoamerican Izapan Style Art"; Julia Guernsey; 2006

Google Books: "The Ancient Maya: New Perspectives"; Heather McKillop; 2004

Metropolitan Museum of Art: Deity Figure

Metropolitan Museum of Art: Deity Face Pendant

Mesoweb: Lords of Creation: Supernatural Patrons

Image Credits:
LACMA: Censer Stand Depicting Principal Bird Deity

Metropolitan Museum of Art: Double Chambered Vessel

Metropolitan Museum of Art: Deity Figure

LACMA: Carved Box with Deities