It’s been another year of wacky
winter weather, with more record-breaking warmth and a near-total absence of
snow. It’s seeming more and more like this is the new normal. And unless you’re
a skier, you probably don’t mind. But the warm weather is disrupting the
natural seasonal patterns of local wildlife – what scientists call phenology – and
it has the potential for significant impacts on their long-term survival.
Many people posted pictures of trees and shrubs
budding and blooming in February, when temperatures hit 60 degrees several
times. Early-blooming spring flowers like crocuses and tulips emerged from the
soil even earlier than usual as well. These plants aren’t likely to suffer any
ill effects from their early arrival, however. New England has always had
enough variability in its winter weather that they have evolved to be able to
handle wide swings in temperature.
That’s not to say that they won’t be affected,
though. It takes energy for plants to grow and bloom, and if they start the
process early and then have to shut down again when normal cold temperatures
return, it’s energy they’ve wasted. They may not have enough energy left to try
again at a more appropriate time. While that won’t affect the survival of the
plants, it does mean they may lose an entire year of reproduction if they can’t
bloom when the pollinators are active.
On the other hand, some pollinators – bees
especially – have been observed out and about during our winter warm spells
when there aren’t any flowers to pollinate or nectar to feed upon. For bumble
bees, it’s the pregnant queens that emerge first, and if she uses up all her
energy searching for food that isn’t yet available, she may die, and with her
goes the hopes for her entire colony.
This mismatch in the timing of the emergence of
plants and insects due to the changing climate is affecting bird migration as
well. Many bird species time their migration to arrive in their breeding
location right when an abundance of insects is emerging so the birds have
plenty to eat and feed to their young. But when the insects emerge early, the
peak of their abundance may be over by the time the birds arrive, leaving the
birds with a challenging search for additional resources.
It’s less of a problem for short-distance
migrants, however, than it is for those that travel long distances, like
warblers and vireos that winter in the tropics. Birds that migrate from the
southern United States may notice the signal of a warm winter and early spring
and begin their migration early. But long-distance migrants from Central
America and South America aren’t aware that the weather far to the north has
been unusually warm, so they don’t know to fly north earlier than usual. Those
birds are unlikely to arrive in time for the abundance of insect prey they need
for reproduction.
The migration of amphibians is being affected as
well, even though most travel only a few hundred yards from their wintering
grounds to their breeding ponds. Wood frogs were observed in late February,
long before they should be active, and while they can tolerate freezing and
thawing cycles, what the short winter means for their life cycle is uncertain.
But just because we’ve had a wacky winter doesn’t mean
we won’t have a more typical spring. If we have more seasonable temperatures in
March and April, perhaps things will get back to normal for the local wildlife.
But don’t count on it.
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