Half-Male Half-Female Cardinals: Why It Happens + 6 Rare Sightings

Did you hear about half-male half-female cardinals and wonder if they’re real? Yes! They are rare but very real. 

Scientists discovered a genetic mutation that causes some cardinals to have both male and female characteristics, making them appear half-male and half-female.

I’ve been a backyard birder for more than 25 years and have never seen a half-sider cardinal at my backyard bird feeders.  This unusual bird is so rare, I doubt I’ll ever see one in my yard. But I can still dream, can’t I? 

Just knowing that half-sider cardinals exist sent me straight into research mode. I had to know more about this bird.

So, I investigated the people who actually spotted them in their yards as well as people in the ornithology community who could share the science behind this phenomenon. 

This article is about one of three rare types of cardinals – the half-male half-female. The other two are yellow cardinals and albino cardinals (also known as leucistic birds). 

In this article, I share everything I learned and know about these birds + actual photos proving the half-male half-female cardinals are REAL.

Let’s go! 

What Do Half-Male Half-Female Cardinals Look Like?

Northern cardinal with bilateral gynandromorphism. Photo by Jamie Hill.

The slang term “half-sider” perfectly describes the appearance of this interesting and rare cardinal. It’s half male half female.

Half of the bird’s body looks like the male cardinal with red plumage while the other half looks like the female with her buffy brown feathers. The male parts could be on the left or right with the female being on the opposite side.

What Is the scientific name for Half-Male Half-Female Cardinals?

The official, scientific name for the half-male, half-female cardinal is bilateral gynandromorph. Other scientific terms include:

  • hermaphrodite (yes, cardinals can be hermaphrodites!)
  • tetragametic chimæras
  • chimera

Gynandromorphy also has several street names including:

  • half-male half-female
  • half-sider

6 Recorded Spottings of Half-Male Half-Female Cardinals

half male half female cardinals were sightings shown on US map
Half-male half-female cardinal sightings.

From the most recent to the earliest sightings, here are the documented instances where the half-sider cardinal was observed.

1. Warren, Pennsylvania | 2021

half male half female cardinal sitting on a branch
Northern cardinal with bilateral gynandromorphism. Photo by Jamie HIll.
jamie hill ornotholigist
Jamie Hill

In 2021, Jamie Hill (Ornithologist) spotted a bilateral gynandromorph cardinal in Warren, Pennsylvania.

Jamie shared with me his experience observing and photographing this rare bird. You can find his account on eBird.  

This bird was male on the right side and female on the left side.

2. Erie, Pennsylvania | 2019

Half-male half-female cardinal
Half-male half-female cardinal
Half-male half-female cardinal

Northern cardinal with bilateral gynandromorphism. Photos by Shirley Caldwell.

photo of Shirley Caldwell
Shirley Caldwell.

In 2019, Shirley Caldwell spotted a bilateral gynandromorph cardinal in her Erie, Pennsylvania yard. Shirley told me “it was awesome seeing this cardinal the first time!”.

Two years later another rare cardinal was spotted 60 miles away in Warren, Pennsylvania by Jamie Hill. Jamie and Shirley believe it might be the same bird!

This bird was male on the right side and female on the left side.

Video below shows the actual bird Shirley observed. Shirley captured the video and National Geographic published it.

YouTube video

3. South Bass Island, Ohio | 2011

I decided not to include the bird’s photo because it was deceased.

In 2011, a bilateral gynandromorph cardinal was spotted on South Bass Island (Lake Erie), Ohio. Andrew W. Jones and H. Thomas Bartlett observed the bird as they were banding subjects.

This bird was male on the right side and female on the left side.

Their report states “Jones made the decision to collect the bird” and transfer to an ornithology research center in Cleveland. In other words, they sacrificed the bird’s life for science.

This bird is so rare I find it very sad they decided to end its life.

4. Warrenton, Virginia | 2009

half-male half-female northern cardinal
Northern cardinal with bilateral gynandromorphism. Photo by Don Maiden

In 2009, Don Maiden spotted a bilateral gynandromorph cardinal around Warrenton, Virginia.

This bird was male on the right side and female on the left side.

5. Rock Island, Illinois

A photo of this bird was not available.

In 2008, a bilateral gynandromorph cardinal was spotted in Rock Island, Illinois. News of this rare sighting made its way to two ornithologists, Brian D. Peer and Robert W. Motz, who traveled to the site and observed the bird for 2 years.

This bird was male on the right side and female on the left side.

6. Nashville, Tennessee

A photo of this bird was not available.

In 1954, Amelia R. Laskey spotted a bilateral gynandromorph cardinal in Nashville, Tennessee.

This bird was male on the right side and female on the left side.

Amelia R. Laskey was an Ornithologist and an important contributor to avian science. She banded the rare bird and made an unusual observation as well: the crest was primarily female buffy brown feathers. 

While there may have been other legit sightings, they’ve not been confirmed or supported with evidence.

What Causes the Cardinal to be A Half-Male Half-Female?

The cause of the half-male half-female cardinal is its sex chromosome makeup. In non-scientific terms, the cells are mixed up.

The sex cells in birds are called Z and W.  The normal male has two ZZ sex chromosomes while normal female birds have one ZW sex chromosome.

When a female egg cell develops with two nuclei—one with a Z and one with a W—and it is “double fertilized” by two Z-carrying sperm, gynandromorphism occurs.

How rare is a half-male half-female cardinal?

Half-male half-female cardinals are very rare. In fact, bilateral gynandromorphism is rare across the animal kingdom. It’s just easier to spot in a northern cardinal.

Why is bilateral gynandromorphism easy to spot in northern cardinals?

Northern cardinals have sexual dimorphism which basically means the male and female colors are different. The plumage in males is red while the females have light buffy-brown plumage with a white belly. 

male cardinal colors
Unique color attributes of the male cardinal compared to the female cardinal.
what a female cardinal looks like
Unique color attributes of the female cardinal compared to the male cardinal.

Most bird species have monomorphism meaning the male and female appear basically the same. Spotting bilateral gynandromorphism in other species of birds (monomorphic birds), is near to impossible.

In their normal state, the male and female look the same so how would the average person notice if one side or the other were different? They wouldn’t.

This would explain why bilateral gynandromorphic cardinals are so obvious when seen.

Can Half-male Half-female cardinals reproduce?

half-male half-female northern cardinal
Half-male half-female northern cardinal. photo by Don Maiden

According to Jamie Hill, the Ornithologist who studied the bird spotted in Pennsylvania, cardinals with bilateral gynandromorphism could theoretically reproduce.

Since the bird is genetically half-male half -female (it has a single testis and a single ovary), reproduction could happen one of two ways:

  1. The bird could mate with a normal male cardinal and lay fertile eggs.
  2. The bird could mate with a normal female cardinal by providing the sperm needed to fertilize her eggs (you know, bird sex). 

That said, after The Wilson Ornithological Society observed one bird with Bilateral Gynandromorphism for 40 days, the reality of reproduction may be as rare as the condition itself. The researchers  noted these observations about the bird:

  • It never paired with another cardinal.
  • It was never heard singing (a key activity that’s part of the mating ritual).
  • It was never heard calling or chirping (behaviors associated with guarding territories and alerting their mate).

Also, Daniel Hooper, Ornithologist, made this comment regarding the rare cardinal spotted in Erie, Pennsylvania “Most gynandromorph individuals are infertile, but this one may actually be fertile as the left side is female, and only the left ovary in birds in functional.”

This is great news because 5 of the 6 sightings of this rare bird had the female (and her functioning ovary) on the left side.


The rare bird referred to as the half-male, half-female cardinal is real. It’s a rare condition caused by a genetic defect and is known as bilateral gynandromorphism in the scientific community.

In more than 40 years there have only been five official sightings of this bird.

Scientists believe a cardinal with this condition could reproduce but do not have evidence that it’s ever occurred. Since they have both male and female sex organs, mating could occur with a male or female cardinal!

So what do you think? What’s the most unbelievable fact you learned from this article?

If you have seen a bilateral gynandromorphic cardinal and have a photo to back it up, please leave a comment below and let me know!

Happy Birding!


Jamie Hill, Ebird.

Brian D. Peer, Robert W. Motz; Observations of a Bilateral Gynandromorph Northern Cardinal (Cardinalis cardinalis). The Wilson Journal of Ornithology 1 December 2014; 126 (4): 778–781.

Andrew Jones, H. Thomas Bartlett; A Bilateral Gynandromorph Northern Cardinal from South Bass Island. Ohio Biological Survey, Inc. 2017; 7: 14-16.

Bilateral Gynandrism in a Cardinal and a Rufous-Sided Towhee. Amelia R. Laskey || Auk 1969, 86(4 (October-December)):760.

More than 25 years ago, Tammy put her first bird feeder outside her kitchen window. Since then she learned how to attract wild birds to her backyard. Studying the meaning & symbolism of wild birds is also a passion of hers. Read more about Tammy

Leave a Comment