Evolutionary Behavioral Ecology

Welcome to the Riehl Lab! We study the ecology and evolution of avian behavior, especially cooperative behavior, mating systems, and parental care. How do natural selection, phylogeny, and ecology interact to shape the diversity of social systems that we see in birds today? How do cooperative societies evolve? How do the challenges of social life affect selection on cognition, communication, recognition, and learning?  And how do cooperative groups protect themselves against parasites and cheaters? We use a combination of field and molecular approaches to answer these questions, with field work in Panama, the Dominican Republic, Colombia, Argentina, and the U.S.
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  Cooperation

This nest contains the eggs of three female greater anis, who are unrelated to each other, can't recognize their eggs or offspring, and share parental care of the mixed clutch. How do complex cooperative interactions like these evolve between genetically unrelated individuals?
© 2016 Christina Riehl

  Parasitism

Brood parasitism is common in birds, both within and across species. Neotropical striped cuckoos (above) are obligate brood parasites, like their European cousins -- but both parasitism and egg mimicry have evolved independently in the two lineages of cuckoos. Why is brood parasitism so common in cuckoos, but so rare in other birds?
© 2016 www.arkive.org

Cognition in the wild

We know a lot about how animals learn and solve problems in captivity, but very few experiments on animal cognition have been done in natural settings. How do animals in social groups learn to recognize other group members, keep track of each others' actions, and collectively make decisions? © 2016 Kamiel Spoelstra
Riehl Lab (and friends) 2025 -
Spring Birding at Turning Basin!
Qwahn Kent, Josh LaPergola, Virginia Heinen, Christie Riehl, Haley Gmutza, Paige Landry, Elisa Yang, Mint Ren, Cynthia Ursino

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Riehl Lab 2023 - Guyot Hall, Princeton NJ
Qwahn Kent, Christie Riehl, Josh LaPergola, Severine Hex, Elisa Yang,
Bre Bennett, Fengyi (Freda) Guo
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                     Riehl Lab 2022 - Celebrating Dr. Savagian!
Maria Smith, Christie Riehl, Amanda Savagian, Meghan Strong, Bre Bennett, Josh LaPergola (not pictured: Trey Hendrix)
(c) 2022 Amanda Savagian
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     Riehl Lab 2019 - Wilson Ornithological Society Meeting
Meghan Strong, Cynthia Ursino, Daniel Baldassarre, Christie Riehl (with Desi), Amanda Savagian, Josh LaPergola, Maria Smith
​  © 2019 Maria Smith
                      Riehl Lab 2016 - Barro Colorado Island, Panama
Luke Carrabia, Vivien Bazarko, Christie Riehl, Amanda Savagian, Meghan Strong, Zach Smart (c) 2016 Christie Riehl
Lab Updates
5/8/25: Congratulations to undergraduate intern Jessica Wang, for winning the Princeton Research Day Orange & Black award for the video that she made about working with Josh on referential calling by greater anis in Panama! Her award-winnning video is available here -- check it out!

5/2/25: Congratulations to Ph.D. student Elisa Yang for passing her qualifying exam with flying colors! Hooray!
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3/20/25: We have a new paper out in Philosophical Transactions on the role that kin competition plays in the evolution of cooperative breeding, with Christie and lead author Antonio Rodrigues. Read it here. This paper was invited as part of a theme issue on the division of labor in animal societies, edited by Barbara and Michael Taborsky and others. Read the whole issue here. 

11/26/24: A new paper is out in PNAS on life history and nest predation rates in tropical birds. Huge congrats to lead author (and former undergraduate lab member) Zach Smart, and co-first author Philip Downing, for building and analyzing this huge collaborative data set. Read the paper here. 

9/13/24: Everyone is back from the field! (California, the Dominican Republic, Panama, and more...) Welcome back to campus!

7/1/24: Congratulations to graduating Ph.D. students Severine Hex and Freda Guo! We will miss you so much!

7/1/24: Congratulations to graduating seniors Kojo Baidoo, Lillith Price-Wharff, Sarah Duntley, and Catherine Garrett! 

6/1/24: Yay! Qwahn Kent was awarded research grants from Birds Caribbean and the Lewis and Clark Fund for Exploration and Field Research! Way to go, Qwahn!

1/1/24: Maria's paper on the distribution of workload and division of labor in greater ani groups is published in Animal Behavior. This was the centerpiece of Maria's dissertation work -- read all about it ​here!

11/1/23: Welcome to visiting Ph.D. student Rafael Fratoni, from Lilian Manica's lab at the Universidad Federale do Parana, Brazil. We're excited to learn more about the blue manakins and their cool lekking behaivor!
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​9/8/23: Welcome to new Ph.D. student Elisa Yang! We are so excited to have you in the lab.
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7/8/23: Maria's paper on feeding synchrony in greater ani groups (or, more accurately, the lack thereof) is published in Behavioral Ecology and Sociobiology (here). A nice way to cap off graduation!

7/1/23: Congratulations to Maria Smith, now Dr. Smith! We will miss you so much!!

7/1/23: Congratulations to graduating seniors Abby Williams and Sam Vasen (who won the Henry Horn prize for the best senior thesis for field work in New Jersey!). Sam's thesis was advised by Trey Hendrix on the Carolina Wren system.

6/30/23: Trey's paper on sex ratio bias in greater ani nestlings is published in Behavioral Ecology and Sociobiology (here), and Trey graduated with his Master's degree! Bon voyage!

5/9/23: Our paper on referential signaling in greater anis is published in PNAS, here. This was such a wonderful and fun group effort: Amanda was the first to realize that anis had a raptor-specific alarm call; Maria and Meghan helped collect data; Josh and Christie did the playback experiments, and Bre assisted with video analysis!  Special props to lead author Josh, who designed the playback experiments and did the heavy lifting.

5/9/23: Christie and Josh were honored to write a Commentary on a recent paper on inclusive fitness in acorn woodpeckers, by Walt Koenig, Sahas Barve, Joey Haydock, and Eric Walters, in PNAS. Our perspective piece is here, and the original article is here. 

1/20/23: Amanda's paper on chorusing in greater anis is published in Ethology, here! It's the cover article of the issue, with a beautiful photo taken in 2018 by former senior thesis student Luke Carabbia. One of the anis in the picture is banded - a female who is still living and is now at least 17 years old! See the cover here.

11/1/22: Amanda's first dissertation chapter, on the honesty of begging signals in nestling anis, is published in Behavioral Ecology and Sociobiology! Read it ​here.

10/18/22: Josh's paper on extra-pair paternity in mainland and island populations of Black Catbirds is out in the Journal of Avian Biology! Read it here. Not only that, it's the cover article -- and Josh painted the cover! See his gorgeous watercolor of a Black Catbird here: www.avianbiology.org/blog/cover-december-2022

​9/1/22: Maria's review of division of labor and workload in cooperative animal societies is published in the Quarterly Review of Biology! What an amazing pandemic project! Read it here. 

8/22/22: A new paper with Zach is out in Current Biology on fluctuating selection on group size in anis. This is the second paper to come out of his undergraduate senior thesis (!). Read it here .

6/15/22: Welcome to new Ph.D. student Qwahn Kent, to start in fall 2022! Yay!

6/13/22: It's the end of an era...Amanda Savagian is now Dr. Savagian! Panama won't be the same next year. Congratulations, Panda!

6/1/22: Congratulations to graduating seniors Willow Dalehite and Emily Sharp, both of whom received departmental awards for their theses and poster presentations!

5/16/22: Josh's paper on alternative reproductive tactics in Hispaniolan woodpeckers is published in Behavioral Ecology and Sociobiology! Read about their odd absence of extra-pair offspring  here. 

3/13/22: A new paper with Mark Hauber and Jeno Nagy is out in Evolutionary Ecology, about the influence of clutch size on egg rejection decisions in hosts of avian brood parasites, here.
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10/15/21: A special issue of the journal Ethology is out, a celebration of the work and career of Michael Taborsky, on the occasion of his retirement from the University of Bern. You can read Christie's contribution here, and the rest of the issue here. 

9/1/21: Congratulations to Amanda Savagian on her dissertation-writing fellowship from the Princeton Institute for International and Regional Studies! And thank you, PIIRS!

8/25/21: A new paper on lifetime fitness payoffs of co-breeding in Acorn Woodpeckers is out in Proceedings B, ​here . Thanks to Sahas Barve for leading this paper! 

6/1/21: Zach Smart's senior thesis work, documenting the effects of the El Nino-Southern Oscillation on tropical birds, is published here in the Journal of Avian Biology! Great work, Zach. 

6/1/21: Welcome to new Ph.D. student Bre Bennett! 
 
3/15/21: Danielle Almstead's senior thesis work, which accidentally documented inter-group conflict by greater anis, is published in Ethology, here! Way to go, Danielle!

6/1/20: Christie has a book chapter in a new book, Unsolved Problems in Ecology, on whether temperate and tropical passerines differ in their mating and pair-bond behaviors. The chapter is here for those who have access; thanks to Andy Dobson, Bob Holt, and Dave Tilman, the editors!

9/1/20: Cynthia, Meghan, and Christie's paper on patterns of parasitism by individual female screaming cowbirds is out in Animal Behavior! Check it out here.

4/1/20: Maria's analysis of skipped breeding and group stability in greater anis is published in Oecologia! Read about it here.

2/2/20: Christie and Mark Elgar have edited a theme issue in Frontiers in Ecology and Evolution on Mechanisms of Communication and Recognition in Social Animals. You can read the entire issue here . There are lots of cool papers but I particularly enjoyed Blake Jones's and Emily DuVal's meta-analysis of social influences on mate choice by females, which is here. 

10/1/19: Dan's postdoc paper on itinerant breeding in Phainopeplas is the cover of the Auk this month! Check it out here.

9/1/19: Welcome to new Ph.D. student Trey Hendrix! We're excited to have him in the lab!

7/1/19: Many thanks to the NSF CAREER program for funding a new grant to investigate female reproductive strategies in anis! 

6/1/19: Farewell and congratulations to graduating seniors Luke Carabbia and Zach Smart, who have been with the ani project for 3 years! Panama won't be the same without them! Both Zach and Luke won Book Prizes from the EEB department for their outstanding theses.

4/1/19: Congratulations to Maria Smith for passing her Ph.D. qualifying exams! 

2/27/19:  Christie and Meghan's new paper on the fitness payoffs of cooperative nesting vs. brood parasitism in anis is published in Nature (here). Many thanks to Andy Zink and John Eadie for contributing a lovely "News and Views" piece on the paper (here). You can also read Christie's "Behind the Paper" blog post here, and check out some media coverage (Science News here, Princeton press release here, Nature podcast here).

2/11/19: Will Feeney and Christie have a new paper out on the evolution of mating systems of obligate brood parasites in a theme issue of Philosophical Transactions B. Read about the paradox of social monogamy in brood parasites here. Thanks to Steve Portugal, Rose Thorogood, and Claire Spottiswoode for inviting us to contribute to this fascinating theme issue on brood parasitism!

1/1/19: Welcome to new postdoc Josh LaPergola, who will be studying group decision-making in anis! 
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9/19/18: A new review paper is out in Proceedings B on the concept of "tipping points" in animal societies and how behavioral ecologists might define and use tipping points in the study of the evolution of cooperation (here). Thanks to Jonathan Pruitt and the Santa Fe Institute for leading this collaborative effort!

7/6/18: A new collaborative paper with Melissa Mark, Mark Hauber, and others is out in the Journal of Chemical Ecology, on the eggshell chemistry of Striped Cuckoo eggs and the Rufous-and-white Wren eggs that they mimic! Not only that, it made the cover! Check it out here.

7/1/18: Farewell and congrats to Dan Baldassarre, who is starting as an assistant professor at SUNY Oswego! We'll miss you, Dan!

6/19/18: A new collaborative paper with Dan, Christie, and others is published in Journal of Avian Biology, on the chemistry of ani egg coloration and how anis perceive it (here). Thanks to Mark Hauber for spearheading this project!

6/15/18: Congratulations to graduating seniors Ellie McNulty,  Mitchel Charles, and Emma Latham (recipient of the department's Book Prize for best thesis in Agriculture!). Stay in touch!

6/1/18: We're excited to start work this year on a new project on collective decision-making in anis. Many, many thanks to NSF!

6/1/18: More congratulations to  Amanda, on receiving a Lewis and Clark grant for this summer's field work!

5/24/18: Many thanks to the Princeton Environmental Institute, for funding an internship for undergraduate Oliver Whang to join us in the field this summer!

4/24/18: Congratulations to Amanda, who passed her Ph.D. qualifying exams with flying colors! 

4/11/18: Christie and Meghan's paper on the fitness effects of social bonds in anis is the cover of Proceedings of the Royal Society of London, Series B! Check it out here.

11/8/17: New paper on reproductive skew in cooperatively breeding birds is out in the American Naturalist (here)! Check out the summary on the AmNat blog here.

10/4/17: Our paper on inter-group competition in anis is published in Animal Behaviour (here).

10/4/17: A collaborative project with Steve Portugal and James Bowen on the mechanical function of vaterite in eggshells is published in The Ibis (here). Read about it on the Ibis blog (here)

9/30/17: Christie is selected as a Kavli Fellow by the National Academy of Sciences.

9/4/17: The end of another field season. Thanks to ani field crew Christa Morris, Zach Smart, Luke Carabbia, and of course Meghan Strong and Amanda Savagian for making it such a success! The anis continued to rebound after the 2015 El Nino with lots of breeding activity; we started a new set of experiments on begging and chick-feeding rules; and we captured extra-group infanticide of nestlings on video for the first time!

6/6/17: Congratulations to graduating seniors Allison Conwell (recipient of a departmental award for outstanding academic performance on her senior oral exam) and Vivien Bazarko (graduating with honors)! Good luck and stay in touch! 

5/8/17: A belated announcement that Cynthia's paper on the genetic mating systems of Baywings (the primary host of the specialist Screaming Cowbird) is out in the Auk (here), and Sarah Porter's undergraduate thesis work on the strange leaf-eating behavior of Crested Guans is out in the Wilson Journal of Ornithology (here). Congrats to Cynthia and Sarah!

5/1/17: Wow! Graduate students Amanda Savagian and incoming graduate student Maria Smith both won prestigious NSF Graduate Research Fellowships! Big kudos to Amanda and Maria!

2/7/17: Congratulations to post-doc Cynthia Ursino, who has won a Fulbright fellowship to come to the U.S. to conduct genetic research in the lab! 

Fall 2016: Post-doc Dan Baldassarre joins the lab to work on the bizarre breeding behaviors of phainopeplas, post-doc Cynthia Ursino joins the lab to work on brood-parasitic screaming cowbirds  (co-advised by Juan Reboreda at the University of Buenos Aires), and Amanda Savagian starts her Ph.D. work on ani vocal communication. Welcome!! 

6/29/16: Research paper on infanticide in communally nesting anis is published in Evolution. Check out the online early version here, and see the press coverage in Science here! 

6/7/16: Traveled to Paris for a fantastic workshop on cheating and mutualisms, organized by Judie Bronstein, Maren Freisen, and Megan Frederickson. Thanks to the Ecole Normale Superieure for hosting and support! Check out the meeting website here.

5/30/16: Congratulations to graduating seniors Haley Gordon and Sarah Porter! Bon voyage! 
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5/9/16: Thanks to the Princeton Environmental Institute for funding our Grand Challenges grant! We'll be looking at the effects that the ongoing El Nino is having on drought, insect abundance, and birds in Panama.

3/12/16: Congrats to Princeton freshman Zach Smart, who was awarded a PEI internship to join the field crew in Panama as a research assistant this summer!

3/1/16: Princeton juniors Allison Conwell and Vivien Bazarko will be joining the lab as senior thesis students -- Allison to study post-fledging care in Florida Scrub-Jays, and Vivien to study facultatively social bees in Panama. Welcome!

2/6/16: Theme issue of Phil Trans B, "The evolution of cooperation based on direct fitness benefits," is online, co-edited by Michael Taborsky, Joachim Frommen, and Christie Riehl! Check it out here.

2/6/16: Review of cheating and punishment behaviors in social animal societies is published in Phil Trans B, co-authored by Christie Riehl and Megan Frederickson. Check it out here.

12/1/15: Commentary on kin recognition in cooperative birds is published in BioEssays, co-authored by Christie Riehl and Caitlin Stern. Check it out here.
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