Washington, June 22 : American scientists have found that the changing climate has led to a significant change in the timings of spring migrations of birds.
Experts at Boston University and the Manomet Center for Conservation Sciences say that many birds are arriving earlier each spring as temperatures warm along the East Coast of the US.
The scientists, however, add that the farther such birds journey, the less likely they are to keep pace with the rapidly changing climate.
They say that they have analysed changed in the timing of spring migrations of 32 bird species along the coast of eastern Massachusetts since 1970.
The researchers say that they gather the necessary data by capturing birds in mist nets, attaching bands to their legs, and later releasing them.
In their study report, published in Global Change Biology, the researchers have revealed that eight out of 32 bird species pass by Cape Cod significantly earlier these days on their annual trek north than they did 38 years ago.
They attribute this change to warming temperatures.
Their study report also highlights the fact that temperatures in eastern Massachusetts have risen by 1.5 degrees Celsius since 1970.
The researchers have revealed that species like the swamp sparrow, which winter in the southern US, are generally keeping pace with warming temperatures and earlier leafing of trees.
According to them, such birds migrate earlier when temperatures are warm, and later when spring is cool.
However, birds like the great crested flycatcher, which spends its winters in South America, are slow to change.
Their migration timings are not changing despite the warming temperatures in New England, say the researchers.
The researchers believe that the difference between the short- and long-distance migrants might be due to the fact that temperatures are linked along much of the East Coast of the US.
Given that an early spring in North Carolina is generally an early spring in Massachusetts, the short-distance migrants can gain insight into when it will be warm further north, and accordingly follow the flush of leaves and insects all the way to their breeding grounds each year.
Long-distance migrants, on the other hand, do not have any good cue for whether it will be an early or late spring on the northern stretches of their migrations because weather in South America has little to do with weather in New England.
The researchers say that being slow to change in response to warming temperatures may have serious repercussions for long-distance migrant birds, for plants bloom earlier in Massachusetts these days than they did in the past.
As temperatures continue to warm, such birds will probably experience environments increasingly different from the ones for which they are adapted.