Category: Blog


Published: December 17, 2013

What can we learn from 30+ years of bird migration data?

Stephanie Ware, Manager, Morphology Labs, SEM


2014 REU Intern Max Witynski


Freshman Environmental Biology and Applied Ecology major at Cornell University

REU Advisors: Dr. David Willard (Adjunct Curator, Birds), Dr. Ben Marks (Collection Manager, Birds) and Dr. Douglas Stotz (Research Ecologist, Action Center)

Symposium Presentation Title: Lessons from 35 years of migratory bird collisions in Chicago

Symposium Presentation Abstract: Bergmann’s rule states that broadly-distributed organisms within a clade average smaller in warmer environments and larger in colder environments. Thus, given the warming climatic trend of the past few decades, one would expect recent adaptation in accordance with Bergmann’s rule to result in smaller body sizes among organisms. The Chicago Bird Salvage Dataset, which is the result of window-casualty collecting at McCormick Place since 1980 and in the Chicago Loop since 2002 and contains a sample size of ~72,000 individual migratory birds, is particularly well suited to analysis of recent morphological changes in North American nocturnal-migrant passerines (songbirds). Sex, age and measurement data have been consistently recorded since the museum first began receiving window-killed birds more than three decades ago. We used R (version 3.1.0) to analyze morphological data on bills, tarsi, wings, and mass for all species with sample size N = 50 to search for evidence of microevolutionary trends over the study period. We found strong negative trends in bill length in the majority of species, suggesting selection for shorter bills has occurred broadly in North American passerines over the study period. Tarsi also showed strong negative correlations in the majority of species, though these trends were not as strong as those for bill. We also found significant but relatively weak negative trends in mass for most species, and a mixture of relatively weak positive and negative correlations for wing length (sometimes considered a proxy for body size). While previous research has illustrated birds’ capacity for rapid morphological change as a response to environmental pressure, most studies have focused more narrowly on island systems or individual species. Our study is unique in describing broad patterns of morphological change across continentally distributed species.

Original Project Title: What can we learn from 30+ years of bird migration data?

Original Project Description: Every spring and fall, large numbers of birds migrating through the Chicago region are killed as they collide with buildings.  For the last 35 years, the Bird Division of The Field Museum has been monitoring bird migration through these collisions at McCormick Place, and over the last 8 years also in the loop region of Chicago.  Over 60,000 specimens have been recovered.  These birds provide a unique data set for analyzing trends in migration and this will be the focus of this internship.  Among the questions to be addressed are 1) whether there have been changes in morphology over the span of the study and 2) what are the effects on bird collisions of lights on versus lights off at McCormick Place.  Development of independent uses of the dataset will also be encouraged.

Research methods and techniques:  REU participant will be trained in museum collection management, morphological data collection, specimen preparation, and data analysis.  Participant will be taught to analyze his/her data with modern statistical methods.  Also included will be literature review and working toward preparing a manuscript for publication.

Stephanie Ware
Manager, Morphology Labs, SEM

Stephanie Ware is currently a research assistant in the Division of Insects currently working with Dr. Petra Sierwald. She also works with Mary Hennen in the Division of Birds monitoring the Peregrine Falcon (Falco peregrinus) populations in Illinois.