Those Late Season Cold Snaps

THOSE LATE SEASON COLD SNAPS

Wednesday, April 11, 2007 (Napanee Beaver)

Friday, April 13, 2007 (Picton Gazette)

The return of more winter-like weather and temperatures over the Easter weekend was a firm reminder that we can’t always depend on the arrival of killdeers and meadowlarks to tell us much of anything. And it isn’t the first year we have had April surprises. It was about this time, in 2003, when a sleet and snow storm persisted for almost a week. While most of the early arrivals had little problem surviving the unseasonable weather, it was a different matter for one other early arrival.

As the snow slowly melted and spring plants began to take on renewed encouragement, other things began to appear in the disappearing snow. Dead tree swallows – in some cases, hundreds of them, littering the backyards and countryside around the Quinte area. Flocks of tree swallows that had arrived in the Quinte area on the heels of the first burst of spring in late March were now dead. Numerous phone calls came in concerning dead swallows littering backyards and carcasses found packed in nesting boxes.

Swallows are the “early birds” of the insectivorous flocks of mixed birds that start returning in the spring, often arriving during periods of snow flurries and cold nights. They have evolved the ability to survive by temporarily switching to a diet of berries and fruit, crowding into crevices to escape the cold, then emerging again to resume their hunt for early spring insects over rivers and open water once the sun shines again. Berries are probably not as succulent as fresh insects caught on the wing over spring waters; however, in a life and death situation, indigestion is likely a better alternative than interment! But the sun never shone for several days, and the temperature continued to hover at late February temperatures. Optimistically, the swallows crowded into nest boxes and other cavities, but froze to death as ice pellets, wind and snow continued to blanket the countryside. It was now too late to attempt reverse migration, a tactic often tried by many species when unseasonable weather hits them in the beaks.

The majority of reports of dead birds that memorable April, came from areas close to water for that was the last hope for catching insects as the swallows snatched what few they could find before seeking refuge in nesting boxes and other cavities to wait out the storm. How could they know the storm would last for days and they would freeze to death first.

One Trenton area resident, who had just moved to her new home a day earlier, was frantic when she phoned after finding several dead swallows in her backyard. According to the caller, she opened the door to a scene of mass destruction, stating that dead swallows littered her backyard, and were falling from the trees as she spoke on the phone. What kind of toxin-filled neighbourhood had she just moved into, she wondered? As she walked around her snow covered backyard, trying to make some sense of the situation, she noticed something sticking out of the entrance hole of a nest box that the previous owner had left attached to the fence. Opening up the box, she was alarmed to find no fewer than 36 dead swallows stuffed in the bird house. The story was the same throughout the Quinte area. The death toll was massive and in my 40 years of being a naturalist I had never witnessed a mortality of a single species to quite compare with that spring’s turn in the weather. However, as the migration continued that month, later arriving tree swallows soon filled the vacancies left behind by the wipe-out. If there was a bright spot anywhere in that story from 2003, it was in the knowledge that the incident affected a prolific species, and recovery of the population was relatively quick.

These images and stories were going through my mind this month as the weather forecast for the Easter weekend caused me to wonder about this year’s tree swallows, and would there be a repeat. Certainly, the purple martin that arrived along Massassauga Road south of Belleville on April 2^nd would not survive the unseasonable dip in temperatures since, unlike tree swallows, they are 100% insect dependent. Birds today must face countless hazards during migration, far beyond what their ancestors had to contend with as they move back and forth between wintering and nesting grounds. Cell towers, TV towers, apartment buildings, skyscrapers, all of them containing lights, get in the way and confuse thousands of birds each year that are programmed to follow stars as guides to their destination. We don’t know how they evolved the ability to use this means to find their way; we just know that they do.

As migrating birds attempt to interpret the glaring lights they see in the distance, they will often collide with the very structure that contains them. The Lennox Generating Station in its early years with its tall chimney and flood lights was responsible one spring for the deaths of over 10,000 songbirds in two nights. Through the efforts of the Kingston Field Naturalists, Ontario Hydro was convinced that strobe lights would have less of an effect and after installation, the deaths dropped to near nil.

Still, most seem to manage and make the perilous journey several times in their life span. Nature often deals a cruel blow and the storm of early April 2003 is an example of what can happen when some birds jump the gun on the spring migration. As predicted, later migrating swallows soon filled the gap left by the thousands who had died. And they began nesting almost immediately upon their arrival, totally unaware that those before them had perished.