American exceptionalism: population trends and flight initiation distances in birds from three continents.

Anders Pape Møller,Patrick-Jean Guay,Diogo S M Samia,Mike A Weston,Daniel T Blumstein,Francisco Moreira

doi:10.1371/journal.pone.0107883

Abstract

BackgroundAll organisms may be affected by humans' increasing impact on Earth, but there are many potential drivers of population trends and the relative importance of each remains largely unknown. The causes of spatial patterns in population trends and their relationship with animal responses to human proximity are even less known.Methodology/Principal FindingWe investigated the relationship between population trends of 193 species of bird in North America, Australia and Europe and flight initiation distance (FID); the distance at which birds take flight when approached by a human. While there is an expected negative relationship between population trend and FID in Australia and Europe, we found the inverse relationship for North American birds; thus FID cannot be used as a universal predictor of vulnerability of birds. However, the analysis of the joint explanatory ability of multiple drivers (farmland breeding habitat, pole-most breeding latitude, migratory habit, FID) effects on population status replicated previously reported strong effects of farmland breeding habitat (an effect apparently driven mostly by European birds), as well as strong effects of FID, body size, migratory habit and continent. Farmland birds are generally declining.Conclusions/SignificanceFlight initiation distance is related to population trends in a way that differs among continents opening new research possibilities concerning the causes of geographic differences in patterns of anti-predator behavior.

Highlights

Many species are currently declining or going extinct in what has been called the sixth mass extinction [1]
The objectives of this study were to: (1) quantify the magnitude of the effect of response to human disturbance as reflected by flight initiation distance (FID) on population trends; (2) test for differences in relationships between population trends and FID among three continents (North America, Australia and Europe) and that such differences may be due to differences in FIDs among species and continents; and (3) test for the joint effect of multiple drivers on population trends including farmland habitat, body mass, migration distance and pole-most breeding latitude
Mean body mass differed significantly among continents with the mean being the smallest in Europe followed by North America and Australia (Welch ANOVA for unequal variances: F = 7.79, d.f. = 2, 80.72, P = 0.0008), but the variances did not differ significantly (Levene’s test: F = 1.62, d.f. = 2, 190, P = 0.20)

Summary

Introduction

Many species are currently declining or going extinct in what has been called the sixth mass extinction [1]. Most animals take flight when approached by humans, and the distance at which this takes place in response to humans or other predators is termed the flight initiation distance (FID). This simple behavioral measure of susceptibility to human proximity and approach reflects an animal’s compromise between benefitting from remaining in-situ in terms of time spent foraging and conservation of energy, and the cost of risk of predation and death (reviewed in [3]). All organisms may be affected by humans’ increasing impact on Earth, but there are many potential drivers of population trends and the relative importance of each remains largely unknown. The causes of spatial patterns in population trends and their relationship with animal responses to human proximity are even less known

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Conclusion