Let’s say you’re a bird, flying north for the spring. You’ve spent the winter in the southern tip of South America, and on your way to the Arctic, you stop in Delaware Bay to feast on horseshoe crab eggs. Only this time, the eggs aren’t there — warm weather arrived early in Delaware this year, pushing the horseshoe crabs to spawn early. Weakened by your trip, without the energy of the eggs, you can’t make it to the Arctic tundra — a habitat that’s also threatened by a changing climate.
That mismatch of migration time and food and habitat resources is what National Wildlife Federation scientists say is an unusually serious threat to birds, whose reliance on multiple habitats make them uniquely vulnerable to changing temperatures. NWF released a report Tuesday that outlines what climate change means for birds and how their challenges, in turn, affect people — in particular the $1.8 billion game bird hunting and $54 billion wildlife watching industries. The report notes that “changes in timing and missed connections” are some of the key threats facing migratory birds as the climate warms.
Migratory birds depend on certain triggers — often changes in daylight or weather, depending on the species — to know when to migrate, and count on food sources being available to them when they arrive in their destination. In some places, springs are starting earlier — last year’s spring was the earliest ever recorded in the U.S. — and in others, they’re starting later than ever. They’re also starting and stopping, with warm weather followed by bitter cold, which can damage new growth on trees and plants and kill off insects that have already hatched. Many of the insects and flowers that birds eat in the spring hatch and bloom when the weather gets warm, so an early or false spring in one part of the world could mean birds arrive in an area with nothing to eat, which could ultimately harm bird populations.
Higher temperatures are jeopardizing birds’ food sources as well. In Maine, thousands of Arctic tern chicks are starving to death, partly because warming oceans are driving the fish their parents need to feed them to move to colder waters. Arctic terns have declined 40 percent over the last 10 years, according to the Fish and Wildlife Service, and the changing climate is having an effect on the birds’ habitats. The NWF report found that, as temperatures have increased over the past four decades, “177 of 305 species of birds tracked in North America have shifted their centers of abundance during winter northward by 35 miles on average,” with some birds moving more than 100 miles northward. Drought threatens to dry up the habitat of birds who live in wetlands, sea level rise threatens coastal birds, and massive pest outbreaks, like the pine beetle, are damaging the forests that many birds depend on to breed. Game birds, like the sage grouse, are particularly threatened by the increasing frequency of wild fires, as well as diseases such as West Nile Virus, which are projected to expand into higher elevations as the climate warms.
The report comes on the heels of another study, published in the journal PLoS One, that found far more species of wildlife will be highly at risk from climate change than previously estimated, including 41 percent of the world’s bird species.
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