London, Sep 26 (ANI): A new study has suggested that birds embarking on long distance migrations are more susceptible to shifts in the climate than ones making shorter journeys.
Scientists have said that 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 have warned that the "increasing ecological mismatch" can lead to a decline in bird populations.
"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," the BBC quoted Nicola Saino of the University of Milan as saying.
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.
"We know that temperatures affect the progress of spring - the higher the temperatures in the first months of the year, the earlier spring arrives," said Saino.
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.
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 Europe," researchers noted.
"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.
"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, said Saino.
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 findings appeared in the journal Proceedings B of the Royal Society. (ANI)