Heavy rainfall triggers increased nocturnal flight in desert populations of the Pacific black duck (Anas superciliosa)

J F Mcevoy,R F H Ribot,J C Wingfield,A T D Bennett

doi:10.1038/s41598-017-17859-0

Abstract

Understanding of avian nocturnal flight comes mainly from northern hemisphere species in seasonal temperate ecosystems where nocturnal flight is often precisely timed and entrained by annual photoperiod. Here we investigate patterns of nocturnal flight in waterbirds of Australian desert ecosystems that fly considerable distances to find temporary water bodies formed from rainfall which is highly unpredictable seasonally and spatially, and when there is sufficient water, they then breed. How they perform these feats of navigation and physiology remain poorly known. Using GPS tracking of 38 satellite tagged Pacific black ducks (Anas superciliosa) in two contrasting ecosystems, before and after heavy rainfall we revealed a key role for facultative nocturnal flight in the movement ecology of this species. After large rainfall events, birds rapidly increased nocturnal flight activity in the arid aseasonal ecosystem, but not in the mesic seasonal one. Nocturnal flights occurred throughout the night in both ecosystems. Long range flights (>50 km in 2 hours) occurred almost exclusively at night; at night the distance flown was higher than during the day, birds visited more locations, and the locations were more widely dispersed. Our work reveals that heavy rainfall triggers increased nocturnal flight activity in desert populations of waterbirds.

Highlights

Levels of nocturnal activity in animals change over time in response to environmental cues such as lunar cycles[1,2,3,4], annual photoperiod, temperature, rainfall and food availability[5,6,7]
Improved understanding of avian nocturnal flight has benefits spanning from conservation, such as better estimates of population size and reserve design[24], to potentially human health, as long-distance flights of waterfowl have often been implicated in the global spread of avian influenza[25]
Our study is the first to show that waterfowl can facultatively adjust levels of nocturnal flight in response to intense rainfall, and we show the effect varied with ecosystem

Summary

Introduction

Levels of nocturnal activity in animals change over time in response to environmental cues such as lunar cycles[1,2,3,4], annual photoperiod, temperature, rainfall and food availability[5,6,7]. In some migratory bird species, annual changes in day length trigger changes in physiology and behaviour in preparation for migration at night, via an endogenous ‘clock’ that regulates the rhythm of diurnal and nocturnal activity[8,9,10,11,12] These normally diurnal birds commence nocturnal migratory restlessness on days coinciding with their migratory departures[13,14,15]. Successful reproduction for many species depends on an ability to respond rapidly and effectively to such massive changes in resource availability[32,34,35,36,37,38] Under such conditions, many nomadic waterbirds move inland from coastal refugia[39,40], and some species can remain inland throughout long drought periods[41]. If exploratory flights are part of the behavioural adaptations allowing exploitation of ephemeral desert wetlands, we expected that major rainfall events would trigger increased flight in the AA ecosystem but not in the MS ecosystem

Methods

Results

Conclusion