Atmospheric conditions create freeways, detours and tailbacks for migrating birds
J Comp Physiol A
Atmospheric conditions create freeways, detours and tailbacks for migrating birds
Judy Shamoun?Baranes 0 1 2
Felix Liechti 0 1 2
Wouter M. G. Vansteelant 0 1 2
0 Theoretical and Computational Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam , P.O. Box 94248, 1090 GE Amsterdam , The Netherlands
1 Vansteelant Eco Research , Dijkgraaf 35, 6721 NJ Bennekom , The Netherlands
2 Department of Bird Migration, Swiss Ornithological Institute , Seerose 1, 6204 Sempach , Switzerland
The extraordinary adaptations of birds to contend with atmospheric conditions during their migratory flights have captivated ecologists for decades. During the 21st century technological advances have sparked a revival of research into the influence of weather on migrating birds. Using biologging technology, flight behaviour is measured across entire flyways, weather radar networks quantify large-scale migratory fluxes, citizen scientists gather observations of migrant birds and mechanistic models are used to simulate migration in dynamic aerial environments. In this review, we first introduce the most relevant microscale, mesoscale and synoptic scale atmospheric phenomena from the point of view of a migrating bird. We then provide an overview of the individual responses of migrant birds (when, where and how to fly) in relation to these phenomena. We explore the cumulative impact of individual responses to weather during migration, and the consequences thereof for populations and migratory systems. In general, individual birds seem to have a much more flexible response to weather than previously thought, but we also note similarities in migratory behaviour across taxa. We propose various avenues for future research through which we expect to derive more fundamental insights into the influence of weather on the evolution of migratory behaviour and the life-history, population dynamics and species distributions of migrant birds.
Birds; Biologging; Flight behaviour; Radar; Weather
Introduction
During migration, birds must contend with an
environment which is highly dynamic in space and time, and they
must do so efficiently. As birds can transverse hundreds
to thousands of kilometres in a single flight, tens of
thousands of kilometres within a migration season and
perhaps hundreds of thousands of kilometres in a lifetime it
may be easy to take for granted just how sophisticated the
adaptations must be for dealing with such a complex
environment, the aerosphere. Scientists have been studying the
impact of weather on migration for decades
(e.g. Smith
1917; Mackintosh 1949; Lack 1960a)
. For the vast
majority of the 20th century studies were often limited in their
spatial scope due to the technical difficulties in monitoring
migratory movements. These studies were often based on
visual observations
(Ferguson and Ferguson 1922;
Lowery 1945; Beth 1961)
or local radar systems
(Lack 1960b;
Nisbet and Drury 1968; Bruderer 1971; Gauthreaux 1971)
(Fig. 1). While visual observations may have a restricted
spatial extent, constant effort sites and observation
networks created opportunities for long-term studies and
enabled researchers to identify recurring patterns of migration
and elucidate how birds respond to weather
(Allen et al.
1996; Maransky et al. 1997; Shamoun-Baranes et al. 2006)
.
In recent decades new measurement and modelling
techniques have greatly facilitated studying how birds respond
to weather and what the consequences are for individuals
or populations, facilitating a new age of research and
discovery (Fig. 1). Biologging techniques enable researchers
to study individual response to weather and other external
factors along entire flyways (Fig. 2), over sea as well as
over land
(Gill et al. 2014; Vansteelant et al. 2015; Nourani
et al. 2016; Weimerskirch et al. 2016)
. With high
resolution GPS tracking and additional sensors such as
accelerometers or heart rate monitors it is increasingly feasible to
measure fine-scale changes in flight behaviour and flight
energetics in response to the aerial environment
(Bishop
et al. 2015; Sherub et al. 2016; Vansteelant et al. 2017a)
.
The use of operational weather radar networks, in some
cases combined with citizen science based field
observations, enable researchers to study migration phenology and
altitudinal distribution in relation to weather over much
larger areas than previously possible
(Shamoun-Baranes
et al. 2014; La Sorte et al. 2015b; Horton et al. 2016a)
.
Simulation modelling and biologging have created
opportunities to study potential cumulative effects of behaviour
for an individual as well as population level consequences
of individual behaviour (Fig. 2)
(Stoddard et al. 1983; Erni
et al. 2005; McLaren et al. 2012)
. Theoretical studies with
analytical models have defined clear benchmarks or
boundaries within which we expect migratory behaviour to occur
generating hypotheses which can be tested in the field
(Ale (...truncated)