Contributions from en route weather amelioration to spring arrival
advancement of long distance passerine migrants
- Mark Eddowes
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Abstract
The interannual variation in arrival timing of Whitethroat in England is
strongly correlated with temperature and wind speed at locations to the
south, along the migration route through Europe, with higher
temperatures and lower wind speed, in particular at more northerly sites
in France, associated with earlier arrival. Analysis of en route weather
conditions demonstrates significant warming and wind stilling during the
migration period in recent years, suggesting a potential role for
amelioration of weather conditions in the observed advancement trend of
arrival. When linked to the meteorological trends, quantified reaction
norms derived from the interannual variations indicate that perhaps
close to half of the recently observed arrival advancement for this
species might be explained by plasticity of this sort. According to this
mechanism, less favourable weather conditions that were previously more
prevalent will have retarded progress during migration to a greater
extent prior to recent climate change-dependent amelioration of the
weather which now reduces delays to onward migration. However, the wider
literature indicates that there has been advancement of Mediterranean
passage of long-distance passerine migrants of a similar magnitude as
the advancement of Whitethroat arrival in England, suggesting a limited
role for this proposed mechanism. Earlier arrival in these European
passage areas may offset the potential for further advancement due to
warmer temperatures and lower wind speeds. It may mean that birds will
continue to encounter similar meteorological conditions as was
previously the case but, having advanced passage of the Mediterranean,
slightly earlier in the year and so providing for progress through
Europe at a broadly similar, meteorologically moderated rate.
Amelioration of en route weather conditions may still make an important
contribution to arrival advancement since, without it, earlier arrival
in Europe could result in increased delays to onward migration.05 Apr 2024Submitted to Journal of Avian Biology 06 Apr 2024Submission Checks Completed
06 Apr 2024Assigned to Editor
29 Apr 2024Reviewer(s) Assigned