Climate risks greater for long distance migratory birds

25.9.2010   (BBC)

Birds embarking on long distance migrations are more vulnerable to shifts in
the climate than ones making shorter journeys, a study suggests.

Scientists say the increasingly early arrival of spring at breeding sites in
Europe makes it harder for the birds to attract a mate or find food.

The researchers warn that the “increasing ecological mismatch” can lead to a
decline in bird populations.

The findings appear in the journal Proceedings B of the Royal Society.

“The study was based on a very large dataset of 117 migratory bird species that
migrate from Africa or southern Europe to northern Europe, covering about 50 years,”
explained co-author Nicola Saino, from the University of Milan.

The international team of researchers, from Italy, Germany, Finland and Russia,
wanted to see if the spring arrival time of the birds at their breeding sites
had changed over the past half century.

To achieve this, they used the birds’ average arrival days at a number of bird
observatories in northern Europe.

The team then compared this information with the corresponding year’s “degree
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.

“We know that temperatures affect the progress of spring – the higher the temperatures
in the first months of the year, the earlier spring arrives,” Professor Saino
told BBC News.

‘Missed opportunities’

Earlier this year, researchers from the UK’s Centre for Ecology and Hydrology
published a study that suggested that spring was arriving in the UK 11 days earlier
than 30 years ago.    
Professor Saino and the team found that spring was beginning earlier, which had
a consequence for the migratory birds.

“The birds that have not kept track with the changes have declined more in northern

These were primarily species making long distance migrations from sub-Saharan
areas, a diverse set including ducks, swallows and warblers.

“The most likely problem is that there is optimum time in spring for the birds
to breed; and by arriving late, the birds are probably missing the best period
in which to breed,” he said.

“Peaks in food abundance, such as insects, are very narrow in northern latitudes;
so if you arrive too late and miss the peak, then you miss the best opportunity
to raise your offspring.

He added that this “ecological mismatch” was likely to be the main reason for
the decline in the birds’ populations.

The data show that the birds are reaching the breeding sites earlier, but not
early enough to keep aligned with the advance of spring.

The long-term consequence could be that populations continue to decline, but
Professor Saino cautioned that it was a complex issue.

“It also depends a lot on what is happening in the winter,” he suggested.

“One of the reasons why they might not be able to keep track of the changes is
that they are unable to shift their winter sites northwards.

“Or they may have to shift their wintering sites southwards, which will make
their journey longer.”


Related articles:

  • Season shifts ‘alter food chains’ 09 FEBRUARY 2010, SCI/TECH
  • Birds ‘off the pace’ with warming 20 AUGUST 2008, SCI/TECH
  • Great tits cope well with warming 08 MAY 2008, SCI/TECH


    Climate warming, ecological mismatch at arrival and population decline in migratory


    Climate is changing at a fast pace, causing widespread, profound consequences
    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.

    details and authors etc at



    see also



    Why action is needed to help wildlife adapt

    Studies of the global impact of climate change on wildlife have rightly made
    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.

    The ways in which climate change will impact on wildlife are quite complex and
    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.

    Many birds may also be affected on their migrations. Habitats may change in stop-over
    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

    Along with Cambridge and Durham universities, we have published a Climatic Atlas
    of European Breeding Birds, the overall messages from which are stark.

    At 3 º C average global temperature rise, the potential future range of the average
    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.

    Yet these projections take account only of future climate conditions – and birds
    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
    land management.

    Already seeing a shift

    However,  the impacts of climate change are not just for the future. We’re already
    picking up a wide range of signals across the natural world that change is already
    with us.

    Spring is coming around 11 days earlier than 30 years ago. We’ve seen appalling
    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.

    Our bold, ambitious Futurescapes programme, is a key part of  our action to help
    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.