Climate risks greater for long distance migratory birds
the climate than ones making shorter journeys, a study suggests.
Europe makes it harder for the birds to attract a mate or find food.
decline in bird populations.
migrate from Africa or southern Europe to northern Europe, covering about 50 years,”
explained co-author Nicola Saino, from the University of Milan.
wanted to see if the spring arrival time of the birds at their breeding sites
had changed over the past half century.
observatories in northern Europe.
days”, which refers to the total of average daily temperatures above a threshold
that will trigger natural cycles, such as plants coming into leaf or flower.
in the first months of the year, the earlier spring arrives,” Professor Saino
told BBC News.
published a study that suggested that spring was arriving in the UK 11 days earlier
than 30 years ago.
a consequence for the migratory birds.
areas, a diverse set including ducks, swallows and warblers.
to breed; and by arriving late, the birds are probably missing the best period
in which to breed,” he said.
so if you arrive too late and miss the peak, then you miss the best opportunity
to raise your offspring.
the decline in the birds’ populations.
early enough to keep aligned with the advance of spring.
Professor Saino cautioned that it was a complex issue.
that they are unable to shift their winter sites northwards.
their journey longer.”
for living organisms. Failure to adjust the timing of life-cycle events to climate
may jeopardize populations by causing ecological mismatches to the life cycle
of other species and abiotic factors. Population declines of some migratory birds
breeding in Europe have been suggested to depend on their inability to adjust
migration phenology so as to keep track of advancement of spring events at their
breeding grounds. In fact, several migrants have advanced their spring arrival
date, but whether such advancement has been sufficient to compensate for temporal
shift in spring phenophases or, conversely, birds have become ecologically mismatched,
is still an unanswered question, with very few exceptions. We used a novel approach
based on accumulated winter and spring temperatures (degree-days) as a proxy for
timing of spring biological events to test if the progress of spring at arrival
to the breeding areas by 117 European migratory bird species has changed over
the past five decades. Migrants, and particularly those wintering in sub-Saharan
Africa, now arrive at higher degree-days and may have therefore accumulated a
‘thermal delay’, thus possibly becoming increasingly mismatched to spring phenology.
Species with greater ‘thermal delay’ have shown larger population decline, and
this evidence was not confounded by concomitant ecological factors or by phylogenetic
effects. These findings provide general support to the largely untested hypotheses
that migratory birds are becoming ecologically mismatched and that failure to
respond to climate change can have severe negative impacts on their populations.
The novel approach we adopted can be extended to the analysis of ecological consequences
of phenological response to climate change by other taxa.
Received August 19, 2010. Accepted September 1, 2010. © 2010 The Royal Society
headlines: a million species on the path towards extinction by 2050; the end of
polar bears by the 2080s; the collapse of seabird populations. There are some
climate change winners, but the scientists predict that the overwhelming effect
of climate change upon biodiversity will be damaging.
all of them interact. They fall into the following broad categories:
Impacts on ‘climate space’: favourable climate conditions are moving location, causing species distribution
to shift typically north and uphill.
Changes in the timings of seasonal events such as hatching of insects in spring: these can change the availability of food for young birds, leading to their
The impacts of extreme weather events: extreme events such as storms and droughts can kill individuals through cold,
wet or starvation. Where these become more frequent, they can have effects at
the population and species level.
Changes in community ecology: changes to competitive advantages between species and the spread and impacts
of invasive species and diseases are likely to lead to markedly different communities
of species than those we know now.
Changes in land use and management: as the climate changes, farming, forestry, water management and many other land
uses are likely to change with it. These activities are all-important for wildlife,
and the way they adapt may offer both opportunities and threats to biodiversity.
locations; hostile areas may get larger; changes in wind patterns may hinder movement;
and of course birds require suitable conditions at both ends of their migration
of European Breeding Birds, the overall messages from which are stark.
species is predicted to shift nearly 340 miles (550 km) north-east. For some species,
the potential future range does not overlap with the current range at all, and
there’s an average overlap of current and potential future range of only 40 per
cent across all species. The average potential future distribution shrinks by
20 per cent.
need suitable habitat in their new climate zones, and the ability to get there.
Clearly, future changes in species distribution of this magnitude are not all
going to happen without considerable helping hand from nature conservation and
Already seeing a shift
picking up a wide range of signals across the natural world that change is already
breeding failures in some seabirds, due to food shortages caused by the changing
ecology of warmer UK seas. We’re seeing early examples of range shifts, with the
spread of little egrets and Dartford warblers helped by warmer average temperatures
in southern England. Our own management of nature reserves is starting to adapt
to changing climate conditions, particularly in our coastal and wetland sites.
wildlife adapt. Creating habitats for wildlife in the broader countryside, beyond
nature reserves, will provide new places for wildlife to live and help the movement
of wildlife required by changing climate conditions.