A Natural View: When Birds Arrive Much Too Early

Terry Sprague 

When birds arrive too early in the spring, some can resort to berries, if there are any left.
Photo by Derek Dafoe.

[This article ran in the April/May 2017 issue of The SCOOP.]
One would have to be totally out of touch with the outdoor world if they didn’t notice the early spring migrants long before spring even officially arrived this year. No, I am not talking just red-winged blackbirds and grackles, but others that put in their first appearance weeks ahead of schedule.  
It started with meadowlarks in our area on February 26, several weeks ahead of schedule. Then it was the northern pintails at Presqu’ile Park, also early, followed by earlier than usual woodcocks on the 28th, and killdeers on the same date. It was a good thing that tree swallows didn’t jump on the bandwagon too, as the thermometer dipped to January temperatures only a few days later. Although record early for some, we can expect to see such early arrivals when the weather conditions are right like they have been this spring, but the discovery of a pine warbler on March 18 one year in a picnic area along the Trent River in Trenton was a complete surprise. We tend not to think much about insectivorous warblers in March – we don’t even think of them much during April, although a few do arrive late in the month. They are predominantly May migrants. That’s when we get psyched up for warblers. Pine warblers are hardy and have been known to appear at bird feeders in winter, and they are indeed early migrants. But, not this early. This one was in full song and acted like a migrant rather than one that had overwintered – a very early migrant, by at least four weeks. 
One mid-March day in 2012, on the Tetsmine Lake hiking trail at Frontenac Provincial Park, we chalked up an unbelievable list of five frog species calling away in collective happiness – chorus frogs, wood frogs, leopard frogs, mink frogs and spring peepers. Some of them were a month early.  
So, what are the implications when wildlife responds to weather that goes up and down like a yo-yo? For frogs, no real problem since the early ones are specialized to handle weather when temperatures plummet. They simply return to torpor and wait for conditions to improve, while those species that typically sink to the bottom of ponds are still snoring away waiting for the water to warm up to heated swimming pool conditions. 
For some, like insectivorous tree swallows, it can spell doom. Tree swallows can resort to berries, but at this time of the year, the previous year’s crop has been all but consumed by the winter population of other species. The thousands of robins that overwintered all over eastern Ontario this year were hard on them, and few are left. Berries are not as palatable to desperate tree swallows as soft insects, we suppose, but indigestion is likely a better option than interment if berries are still available. We all remember the tragic deaths of many thousands of tree swallows that perished in the Belleville and Trenton area on April 15, 2003, when a late snowstorm with sleet persisted for several days. In Trenton, hundreds of tree swallows were seen skimming the surface of the Bay of Quinte for the few remaining insects that were available. By morning, all were dead, in one case, a nest box found crammed full of almost 40 tree swallows that had likely crawled in to escape the cold, only to succumb to suffocation instead. It was tragic, but later migrants soon filled the void. It happens sometimes.  
But what about long-term changes, where global warming is upsetting migration patterns? For centuries, migration has operated like a finely tuned clock. Over the years, we have even established average arrival dates for migratory birds, and binoculars are poised on those dates to catch sight of specific migrants – now, we don’t know when to expect anything. Killdeers in February, tree swallows in mid-March? What’s going on here? 
So, does the early bird really get the worm? Not always, especially in the case of woodcocks during that fateful April spell in 2003 when large numbers of them were seen desperately probing for worms in roadside ditches – the only soft mud available to them. Doubtless, many died.  
Species that have adapted to subtle changes over millennia are now being expected to make adaptations to climate change quickly because of the swift rise in temperatures. Failure to adapt spells doom to their survival as a species. Tree swallows and other insectivorous birds may arrive too early, or conversely, too late, and find their regular diet of insects, plankton or fish either lacking or absent. Some birds are specialized feeders and must time their arrival just right to harvest their favourite food.  
There are advantages, of course, to migrating early. If the weather cooperates, then the early birds have the first choice when it comes to breeding habitat, and if the weather continues to favour them, they have the ability to increase their brood size or be able to squeeze in another brood beyond their usual one, two, or three.  
It seems that we are in the early stages of global warming, or climate change if you prefer. Call it what you may, but we are to blame. Bird species are already demonstrating the effects of some of these changes in regions ranging from the Arctic and Antarctica to the tropics. These changes can be tracked from the level of individual species all the way up through entire communities, and the evidence that is available so far shows that global warming is already affecting some birds and, ultimately, biodiversity. There is a general scientific consensus that global warming has already had a profound effect on biodiversity and will continue to be a primary cause of the loss of biodiversity. Habitat destruction and fragmentation are currently still the greatest threats; however, we will have to wait before we can understand fully the implications of global warming and what species, especially birds, are able to adapt.  
For more information on birding and nature, check out the NatureStuff website at www.naturestuff.net. Terry Sprague lives in Prince Edward County and is self-employed as a professional interpretive naturalist.