Barn swallows long-distance migration occurs between significantly temperature-correlated areas

Mattia Pancerasa,Nicola Saino,Roberto Ambrosini,Renato Casagrandi

doi:10.1038/s41598-018-30849-0

Mattia Pancerasa, Nicola Saino + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-30849-0

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Abstract

Organisms are routinely confronted with crucial decisions on the best time and place to perform fundamental activities. However, unpredictable spatio-temporal variation in ecological factors makes life-history optimization difficult particularly for long-distance migrants, which are putatively blind of conditions thousands of kilometers and weeks ahead along their journey. Here we challenge, on a hierarchy of geographical scales, the common wisdom that migratory birds have no clue to ecological conditions at destination. Using ringing data of the inter-continental migrating barn swallow (Hirundo rustica), we show that temperatures at breeding sites and at times of arrival from migration are more correlated with those at actual wintering sites and at times of departure than with those at other sites and at periods before/after departure. Hence, individual swallows have clues to adjust timing of spring migration based on expected conditions at destination, and they apparently choose wintering sites to increase availability of such information.

Highlights

In natural populations, organisms are expected to do the right thing at roughly the right place and time, under the limits set by their physiological and behavioural constraints, because natural selection strongly penalizes the individuals that do not appropriately match their activities to current environmental conditions[1,2]
We estimated the putative departure time from Africa when spring migration started according to information from a recent geolocator study[35] and from bird monitoring[36], and spring arrival time to the breeding site in Europe according to a model of the progress of spring arrival of barn swallows[37]
The timing of spring migration is believed to be deeply rooted in endogenous, genetic mechanisms[8,39,40]

Summary

Introduction

Organisms are expected to do the right thing at roughly the right place and time, under the limits set by their physiological and behavioural constraints, because natural selection strongly penalizes the individuals that do not appropriately match their activities to current environmental conditions[1,2]. It may even be expected that, in order to appropriately tune their decisions on timing of migration and arrival to the breeding sites, migrants choose as wintering areas those where the most accurate information on future conditions at destination can be gathered This may partly contribute to the migratory connectivity that migratory birds exhibit, whereby individuals that breed in the same geographical region tend to share the same wintering area[25,26,27,28,29,30,31], but see Finch et al.[32]. We test the prediction that temperatures at the sites where barn swallows spend their wintering period in Africa are highly correlated with those recorded at the breeding sites weeks later, when migration is completed, as expected under the hypothesis that individual barn swallows choose their wintering areas depending on the level of temperature-connectivity with the breeding sites

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