Saturday, March 28, 2020

Warm winter disrupts seasonal patterns

            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.

This article first appeared in the Newport Daily News on March 28, 2020.

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