This meeting and presentation took place entirely online via Zoom.
At 7:00 p.m., President Debbie Mullins called the Society meeting to order.
President Mullins welcomed the attendees and remarked that spring migration was well underway, with participants in that morning’s LSNY Central Park walk having seen close to 50 species, including four warbler species. She noted that the Tuesday walks will continue through the end of May and invited all to come out and join them.
President Mullins also noted the hazards that migrating birds encounter navigating through the city, and, in particular, the confusion and collisions with buildings and windows caused by bright lights. She highlighted the legislation that is coming up for a vote this summer in the New York City Council to require that non-essential lights be turned off during periods of peak migration, and said that the Linnaean Society will be working to support this effort.
The upcoming spring Birdathon, which is a fundraiser run by the Linnaean Society for the Great Gull Island Project, will be held May 11 and 12. Details regarding participation will be emailed soon.
Society members had been asked to vote online on two motions in advance of this meeting:
Motion 1: Request to approve the minutes of the February, 2024, general meeting. The minutes were approved by a vote of 129 in favor, 2 abstaining, and none opposed.
Motion 2: Request to approve the membership applications of seven new members. The vote was unanimous with 131 in favor and none opposed. President Mullins warmly welcomed the following new members:
- Caroline Wolff, Active Membership, Sponsored by Chuck McAlexander
- Joan Felder, Active Membership, Sponsored by Ken Chaya
- Alison Wylegala, Active Membership, Sponsored by Elizabeth Keim and Erika Piik
- Guy Percival, Active Membership, Sponsored by Lisa Kroop
- Jennifer Percival, Active Membership, Sponsored by Lisa Kroop
- Lisa Detert, Active Membership, Sponsored by Karen Becker
- Alexia Fishwick, Supporting Membership, Sponsored by Michelle Zorzi
Speaking to the audience at large, President Mullins encouraged those who aren’t members of the Linnaean Society to join, saying that it is open to all. She described the process for joining, noting that details can be found on the Society’s website.
At 7:10 p.m., President Mullins turned to the lecture program and introduced the speaker, Dr. Ben Winger, assistant professor of ecology and evolutionary biology at the University of Michigan and curator of the University of Michigan Museum of Zoology, Division of Birds. Dr. Winger is an ornithologist, with research focusing on the ecology, behavior, and evolution of birds; his presentation, “The Evolution of Seasonal Migration in Birds,” highlighted some of that work.
Lecture: “The Evolution of Seasonal Migration in Birds,” presented by Dr. Ben Winger
Referencing the morning’s LSNY Central Park walk with spring migration being upon us, and the fairly predictable schedule of bird species’ arrivals, Dr. Winger invoked the Yellow-rumped Warbler and the Blackburnian Warbler, species familiar to those who bird here in the spring, as the starting point for a discussion of bird migration and his research on understanding how and why bird migration has evolved.
He began with a discussion of the evolutionary history of bird migration, and how that history has been pieced together. He first described the remarkable long-distance migration of the Blackpoll Warbler from the boreal forests of northern North America, over the Atlantic Ocean and ending in South America. He highlighted how much the habitats at the ends of the journey differ from each other; however, the Blackpoll Warbler is equally comfortable in both, demonstrating that biogeography plays a role in migration. But where were these birds’ ancestral homes? How did their migratory patterns evolve? Did they shift their breeding range north from an ancestral southern range (out-of-the tropics hypothesis), or did they shift their wintering range south (the temperate home hypothesis)? Because the bird fossil record is weak and difficult to interpret, Dr. Winger used a phylogenetic analysis of 120 species of New World emberizoids (warblers, sparrows, blackbirds, orioles, cardinals, buntings, and tanagers) that migrate seasonally between the Nearctic/temperate zones and the Neotropical region to evaluate these hypotheses. His phylogenetic model provided an indication of geographic ranges through historical time by calculating probabilities of ancestral breeding and wintering ranges being in the tropics versus the Nearctic/temperate zones. His results showed that wintering range shifts out of the temperate zone to the south were a more prevalent pattern of migration evolution than breeding range shifts out of the tropics to the north which were rare.
Dr. Winger then moved on to the consideration of why birds migrate and proposed exploring a more general explanation for the evolution of bird migration – one that doesn’t rely on where birds ancestrally originated. Instead, he suggested looking at the movements of birds, distinguishing between the mechanisms of dispersal and migration, and the effects of seasonality. Dispersal is a one-way movement, usually of a short distance. An example is the distance between where a bird is hatched and where it raises its own young. With each dispersal there is an encounter with seasonality, and with changes in seasonality from one dispersal to the next, the bird needs to adapt, or it dies. Thus migration is one possible adaptive response to seasonality. As a population adapts to seasonality, migration can evolve. Rather than escaping from the tropics, Dr. Winger explained, migration has evolved as a response to increasing seasonality across space and time. But escaping seasonality to a new location doesn’t answer why the bird doesn’t just permanently stay there. To address that seeming contradiction, Dr. Winger offered the example of the Blackpoll Warbler, which returns year after year to exactly the same breeding site. Adult migratory birds tend to return to their same breeding sites every year, and this fidelity – known as philopatry – contributes to their reproductive success. Dr. Winger concludes that site fidelity underlies the evolution of bird migration: bird migration evolves as a strategy to escape seasonality, and the return to a known, familiar breeding site results in a good chance of reproductive success.
The phenomenon of bird migration causes competition between reproduction and survival. While the abundant resources of the temperate and Nearctic zones provide environments beneficial to reproductive success, the migratory journey can be hazardous and risky. Earlier in the lecture Dr. Winger had introduced the concept of the slow-fast continuum of life histories, and now he returned to it to evaluate where migrating birds might sit on that continuum. In animals, an example of a fast life history might be the mouse – it develops fast, produces a large number of offspring, and lives a short life – as contrasted with an elephant, which illustrates the slow-end of the life history continuum by developing slowly, producing only a few offspring, and living a long life. To assess migrating birds’ position on this continuum, Dr. Winger compared data of bird species that breed in the boreal zone but migrate varying distances to their wintering grounds; eBird data showed that the time spent on breeding territory decreased with migration distance, as did annual fecundity (annual number of chicks), while annual survival data (from the Institute for Bird Populations) showed that annual survival relative to body size increases with migration distance. Thus field data suggests that long distance migrants fit on the slower end of the life history continuum: the Yellow-rumped Warbler becomes an example of a migratory bird with a fast life history, having a short-range migration and enduring difficult winter conditions, while the Blackburnian Warbler is on the slow life history end of the spectrum, producing fewer annual offspring and yet making a far longer migratory trip. While breeding in the high latitudes produces a faster life history strategy than in the tropics, the evolution of long distance migration slows the life history down.
Dr. Winger summarized his talk, emphasizing that migration and its evolution are geographically complex phenomena, but that phylogenetic studies point to some bird species evolving to migrate from the temperate zone to the tropics as analogous to evolutionary responses to seasonality. As a consequence, the strategy of long-distance migration enables a higher annual survival rate compared to shorter-range wintering in the temperate zone, or not migrating at all.
Dr. Winger concluded by mentioning the troubling large-scale declines in bird populations across the world due to the effects of anthropogenic habitat loss, light pollution, and related hazards. We saw with the life history analysis of long-distance migrating birds that in spite of having evolved high survival rates, these are among the species particularly vulnerable to rapid population decline because of their lower number of offspring and the risks they are exposed to, especially during migration. Dr. Winger commended the Linnaean Society for its efforts on conservation advocacy for birds.
At 7:55 p.m., Vice President Doug Futuyma thanked Dr. Winger for a fascinating lecture. He then hosted the Q&A session.
At the conclusion of the Q&A, Vice President Futuyama thanked Dr. Winger again, and at 8:20 p.m. the meeting was adjourned.
A recording of this meeting in its entirety can be found on the Linnaean Society of New York website.
Respectfully submitted by Lisa Kroop, Recording Secretary