UT's Biodiversity Center Prepares to Learn from Falcon's Eggs

UT Austin's resident peregrine falcon, Tower Girl, has been laying eggs in her nest box in the UT Tower every year since 2016. This year, as in previous years, given the amount of time that has passed since their arrivals, the eggs will not hatch.

​However, the Biodiversity Center, the research unit on campus that hosts the Tower's livestreaming "Falcon Cam," is interested in using this year's clutch to understand more about why the eggs are not hatching. Teaming with two other Texas institutions, Texas A&M and Angelo State University, a team is hoping to learn more. 

"While it is generally our policy to leave Tower Girl's nest alone, she has been absent in recent days, and eggs are clearly not going to hatch this year," said David Hillis, Biodiversity Center director and a professor of integrative biology. "There have been a lot of questions about her in the last year that these eggs can help to answer and let us know if there is anything that we can do in the future to help improve the chances for a successful clutch."

When the remaining eggs in Tower Girl's nest are removed, they will then be taken to Texas A&M for analysis to learn whether the eggs were fertilized. The last time Tower Girl's eggs were extracted in 2017, a similar analysis found the eggs had not been fertilized. However, this year, photographers documented that Tower Girl had mated with a wintering male falcon, so the results could be different this time. 

The team also is exploring the possibility of DNA research to learn more about Tower Girl's origins. After the initial analysis at Texas A&M, the eggs will be transferred to Angelo State, which may conduct the DNA research before installing the eggs in the university's permanent Natural History Collections.

"We've always wondered what peregrine population Tower Girl emanated from," said UT Austin alum Bruce Calder (B.S., '81), who initiated the falcon nest and camera project several years ago. "My hunch is trans-Pecos (Big Bend) area. Hopefully, there are enough data available to make a meaningful correlation."

On campus, Neil Crump, a manager in Project Management and Construction Services at UT Austin, is responsible for the extraction. As Crump explains it, the extraction process is fairly simple and quick, and efforts are being made not to stress the falcon. When Tower Girl is confirmed to be away from her nest, Crump will climb to the nest box area with a hard hat and safety glasses and remove the eggs. He will replace them with replicas, so as to minimize stress on the bird and allow her to naturally finish out her maternal cycle.

The real eggs are placed in an egg carton and transferred to Calder who will bring them to a Texas A&M ornithologist who has all the necessary salvage permits.

The replica eggs will be extracted in a similar manner in late May or early June when the Biodiversity Center also plans to install a microphone near the nest box. (Typically, in the past around late May and early June, Tower Girl has started to remove unviable eggs on her own, indicating there will no longer be a need for replica eggs by then.)

It is not unusual for female birds in the wild to lay eggs that are not fertilized, even if the female has mated with a male. The mating could have been unsuccessful, or one bird might be infertile. In general, only about 1 percent of the billions of wild bird eggs each year actually become adult birds.

Nonetheless, the Biodiversity Center is excited to learn more about our unique resident falcon and to be able to answer the burning question so many of her fans have: Why haven't the eggs hatched?