CREDIT: U.S. Geological Survey
If promptness isn’t your forte, at some point you’ve probably been asked by a friend or relative if it would “really kill you to be early?”
According to new research by the U.S. Geological Survey, the answer, for American White Pelicans at least, is yes.
At a major breeding site in Chase Lake National Wildlife Refuge in North Dakota white pelicans are showing up around 16 days earlier in the spring than they did four decades ago. And while that might be exciting news for bird watchers eager to see the improbably proportioned birds swooping down on Northern lakes again after a long winter away, it can prove deadly timing for delicate hatching chicks.
American white pelicans are one of the biggest birds in all of North America. Standing around four feet tall, with a wing span of nearly nine feet, their ludicrously large pinkish-yellow bills make them instantly recognizable. The birds migrate south in the early fall to their wintering grounds in California, Mexico, Central America, along the Gulf Coast and in Florida. They return north in the spring to breed in parts of western Manitoba and Minnesota westward to northern California. One-half of the entire breeding population of pelicans nest at just 10 sites in the northern plains. The earlier spring migration date is believed to be cued by unusually warm weather in the wintering grounds.
“When the pelicans start to fly north, all they know is what the weather is like where they are,” said Lawrence Igl, a research ecologist at the USGS Northern Prairie Wildlife Research Center. ‘They don’t get the forecast for North Dakota.”
When pelican chicks are born, they are completely naked and are unable to regulate their own body temperature, depending instead entirely on their parents to keep them warm. At about two weeks old, they start to grow cozy down feathers and can shiver to warm themselves up. At this stage, both parents may leave chicks for up to 24 hours to hunt for food. With their reliably warm parents no longer on chick cuddling duty around the clock, baby birds from many different nests huddle together in creches to keep warm. In the days and weeks while these creches are still forming, the chicks are extremely vulnerable to cold, wet weather. And sadly for the chicks, their parents’ early arrival and breeding seem to be exposing them to extreme and unreliably early spring weather, just at the time when they are least able to protect themselves.
Back in 1965, the days when chicks were most vulnerable to plunging temperatures and wet weather was from between June 11 – 25. Between 2004 and 2008, this dangerous transition period occurred between May 25 and June 9, when weather in North Dakota is still extremely unsettled. In 1965, there were just three dangerous weather days for chicks at this stage, in 2004-2008, there were about nine days. Tens of thousands of chicks died in these years. In 2007, for example, researchers recorded 11,262 nests in the Chase Lake study site, but just 531 chicks fledged. In 2008, 11,541 nests were documented, but just 86 chicks survived. In fact, 2006 was the only recent year studied that saw an “average” number of chicks make it through fledging. In that year, 17,302 nests were observed and 11,020 chicks pulled through.
“Pelicans are remarkable in that, unlike so many other birds, they appear to be able to make some changes in their migration schedule to adapt to changes in the climate,” said Igl. “But they are still experiencing the negative impacts of climate change because the timing of the dangerously inclement weather in North Dakota hasn’t shifted in step.”