Snowbound Swallows Fight Back

It has been a bumpy season in Ushuaia. We had all known from the time we arrived that this could be a tough field season—in the past few years at this unforgiving latitude, most of the chicks have died. The unspoken question among our crew was never if some would succumb, but when. Yet little by little, and despite cold, rain, 120 kilometer per hour winds, and storms that tear apart the landscape, we had gotten our hopes up as chicks and their parents pulled through.

Mid-December, however, brought a fatal pair of snowstorms to our site. The first snow day was a warning. We checked boxes and suspended any activities that might stress our birds. A few of our oldest chicks died in a fatal combination of cold and starvation. But the second snowfall, two days later, was the true disaster.

It started during the night. When we awoke that morning, Ushuaia looked like the swirling center of a snow globe. There would be no going to the site that day. Even the next day, after the storm cleared, the fields were still blanketed in several inches of white.

It was too much for our hardy swallows. In other years November frost had taken a toll on some nests, but this mid-December blizzard, analogous to a June snowstorm in the northern hemisphere, was a brutal blow to the roughly 40 nests we had been monitoring.

Nest box checks were a body count. Chicks ranging from a few days old to nearly full size were found frozen. Adults found foraging nearly impossible and could only hope to keep warm. Some abandoned their boxes and others, even more distressingly, were still trying to incubate dead chicks or eggs.

It was a difficult day for all of us. Having heard how seldom adults attempt a second nesting at this latitude, we walked our sites with the sinking conviction that our season was over.

Yet there was still a surprise or two in store for us. The very next day, the fickle climate brought us sunshine, and within a few days it became clear that some of the swallows were still tending active nests, their eggs still warm, their chicks still growing healthily despite the elements.

Perhaps the most gratifying surprise of all, however, was the discovery that within a week of our blizzard some pairs that had lost their broods were trying again. In a remarkable show of pluck, pairs of swallows moved to new boxes and worked furiously to start over.

We were delighted. By January, we had more active nests at our first site than before the snowstorm. This was especially impressive when we considered how much energy they had already expended on their previous nest—and a fantastic way for us humans to begin our own new year.