Experimental Investigation of the Dietary Ecology of the Extinct Passenger Pigeon, Ectopistes migratorius

Ben J Novak,Beth Shapiro,Holland E Shaw,Erika V Novak,James A Estes

doi:10.3389/fevo.2018.00020

Abstract

For tens of thousands of years, passenger pigeons (Ectopistes migratorius) were a dominant member of eastern North American forest communities, with megaflocks comprising up to several billion individuals. The extinction of passenger pigeons in the early 20th century undoubtedly influenced associated species and ecosystems as interactions stemming from the pigeons disappeared suddenly. Here, we strive to better understand what was probably one of the most significant of these interactions – that between passenger pigeons and seed bearing trees. Using the band-tailed pigeon (Patagioenas fasciata) and the rock dove (Columba livia) as physical and ecological proxies, we evaluated passenger pigeon dietary range and potential to disperse seeds. Our findings suggest that the passenger pigeon’s dietary range, observed historically to be taxonomically broad, was constrained to certain seed sizes due to bill gape size. In addition, we conclude that the digestive process invariably destroyed consumed seeds but the potential for a nutrition/dispersal mutualism might still have existed via regurgitation and post-mortem release of crop contents. Our results highlight the range of ecological interactions that can be lost with species’ extinction and the inherent challenge of understanding the consequences of those interactions.

Highlights

For tens of thousands of years prior to their extinction in the early twentieth century, passenger pigeons (Ectopistes migratorius) were the most abundant bird species in North America, moving nomadically, consuming mast, and fruit crops throughout eastern forests in megaflocks containing tens of millions to billions of individuals (Greenberg, 2014; Murray et al, 2017)
Even the smallest gape model indicates that passenger pigeons were able to consume the full size range of white oak seeds obtained from our sampled localities
Seed size distributions for black oak and American chestnut are intermediate between red and white oak, affording a possible refuge in size for a small proportion of the seeds produced by black oak and chestnut

Summary

Introduction

For tens of thousands of years prior to their extinction in the early twentieth century, passenger pigeons (Ectopistes migratorius) were the most abundant bird species in North America, moving nomadically, consuming mast, and fruit crops throughout eastern forests in megaflocks containing tens of millions to billions of individuals (Greenberg, 2014; Murray et al, 2017). Various hypotheses have been advanced for how these megaflocks shaped the distribution and abundance of tree species (Webb, 1986; Ellsworth and McComb, 2003); most of these hypotheses lack convincing evidence and long-term eco-evolutionary forces imposed by passenger pigeons lack attention almost entirely. The degree to which passenger pigeons functioned as seed predators (consumers that destroy seeds) vs seed dispersers (mutualists that disperse seeds) is unknown. These differing ecological roles have distinct evolutionary implications for the forest ecosystem both before and after the passenger pigeon’s extinction

Methods

Results

Discussion

Conclusion