Male  … or female?

For most of the cases seen by Wildlife Center veterinarians each year, the gender of the patient really doesn’t matter — the treatment procedures will be the same.

But when it comes to the Center’s resident corps of education animals, gender becomes more important.  When Center staff visit an elementary school with an education animal, one of the first questions almost invariably is, “Is it a boy, or is it a girl?”  And education animals have names — and we try to select gender-appropriate ones.

With mammals and reptiles, Center staff have an easy time answering this question.  With raptors, this can be a trickier question to answer.

Most raptors do not display a difference in plumage between the sexes (with American Kestrels being one exception), so the weight of the bird is often used as a clue.  Female raptors are typically larger than males, so a particularly large, heavy bird is assumed to be female.  Likewise, the smaller birds are thought to be male. 

However, this doesn’t always hold true — and many times, raptors fall into an “average weight” category, making it difficult to really guess one way or the other. 

The only true confirmation we can receive is through DNA testing or through internally scoping the bird.

When the Center is ready to accept a new raptor into the educational animal ambassador team, the size and weight of the bird are taken into an account, and the staff make an educated guess — sometimes incorrectly, as it turns out.  Based on size, Kettler the Broad-winged Hawk was thought to be a male.  However, after several years of living at the Center, “he” began laying eggs!  

Other past “surprises” have included Buzz, the Great Horned Owl.  For Buzz’s entire life at the Center, Buzz was assumed to be a male — and it wasn’t until after Buzz passed away and a necropsy was performed that the staff realized “he” was actually a “she.”

While a couple of our education raptors have had their DNA tested to determine their gender, the DNA testing isn’t free, so the Center hasn’t done this routinely.  However, thanks to a new WCV volunteer,  Dr. Vince Formica, we’re about to get some additional answers!

Dr. Formica, a post-doctoral research associate at the University of Virginia, is working with colleagues Dr. Elaina Tuttle and Marisa Korody at the Molecular Ecology Laboratory at Indiana State University.  As part of a study to perfect a DNA-based method for sexing birds, Vince and Elaina have offered to use their techniques to determine the sex of some of our education birds.  Because this technique is still in the prototype stages, they cannot be 100 percent sure of the results, but after running a few tests, there will be some fairly conclusive results to share.

A molecular biology lesson from Dr. Vince:

Birds are very similar to humans when it comes to how they end up as males or females; their DNA determines what sex they will be as they develop.  Rather than the X and Y chromosomes that humans have, birds have Z and W chromosomes.  Females birds are the ones with two different types of chromosomes — they have the Z and W — while the males have the ZZ.

To determine the sex of a bird, we extract some DNA from their blood and amplify two different genes.  When we do a molecular analysis with DNA, we can see this amplification in the form of a peak.

Two peaks -- female

In short, if there are two peaks — two different genes – we can be relatively sure the bird is female.  If the individual has only one very clean peak after a few tries, we are confident that the individual is male. 

This DNA technique is very reliable once you have a chance to perfect the method with a number of individuals from the same species — the problem is, very few people have tried to use this method on raptors (especially owls).  Some individual animals can have two peaks, but the second peak might not be a “sex specific peak” — it might be an anomaly that shows up in, for example, all screech owls, and no one knows for sure until we run a number of individuals of the same species.

One peak -- male

For that reason, we’re also running the “male” results (one peak) several times, just to ensure that the second part of the test hasn’t failed. 

Until we get all of the kinks worked out we’ll just have to say we are “pretty sure” of results.

So  … who are the ”unknowns” of the WCV educational animal ambassador team?

Grayson [Broad-winged Hawk]
Gustavo [Barred Owl]
Misty [Barred Owl]
Alex [Screech Owl]
Pignoli [Screech Owl]
Mama G’Ho [Great Horned Owl]
Quinn [Great Horned Owl]
Great Horned Owl #10-2051

Of those eight, Vince has reported results with confidence on three of the birds.  Click here to read results from round one!