April is testing time, as decreed by Mother Nature. Within this month everything must run the gauntlet of a few days of winter, a few days of spring, a day or two of summer, a few days of winter again, and then, maybe, a few days of spring.
To us humans, this fickle pattern of switching to snow boots, rubber boots or hiking boots is a mere annoyance. (Although, admittedly, I am so tired of putting on layers of clothing just to go outside to check the mailbox!) We are prepared to adapt, like it or not, and with long-range forecasts to buoy our spirits we soldier on into the next calendar week.
However, it isn’t so easy if you are a non-human critter trying to get a new year started. Especially if that critter is migratory in nature. Those longish sunny days of false spring tickled the pituitary gland and the call to head north was given. And then it snows again ... surprise!
I have no doubt that many of you have felt the same pang of anxiety as I when observing a tree swallow or robin sitting on a snow-covered branch. “That’s not fair! Poor birds! They are all going to die!” But, maybe not.
Resilience is a trait of Nature that has ensured the eons-long survival of many species. To be resilient is to be knocked down or back and then rally to return as good as new (or almost so) to carry on. April is the month of resilience testing. This is where the phrase, “Whatever doesn’t kill you makes you stronger” probably originated.
To be resilient is not the same as to be resistant. Resistance means that you just shrug off the adversity and carry on. Must be nice, eh? While being resistant may sound like a good thing, in the long run it’s not, evolutionarily speaking. If nothing changes you, you don’t change; however if you are constantly re-evaluating the way you do things due to a series of set-backs, you are growing and adapting.
When we speak of species adaptations, what we are looking at is the current end result of many challenges from which that species has survived. The larger-bodied ones survived. The furriest ones survived. The odd-coloured ones survived. The ones that leave for the winter, survive. They survive because they are resilient and keep getting up again after a series of setbacks.
Outside my window is seen a lovely mature sumac shrub, filled with last fall’s fuzzy fruit clusters, each adorned with several inches of wet snow; sitting beside each fruit cluster is a robin. These robins arrived in our yard about two weeks ago, when the sun was shining and I wore only a light jacket.
These birds of the brick red breasts had been merrily bob-bob-bobbing along across the lawn picking up all sorts of juicy bug larvae that had overwintered under the unraked leaves. But that source of food is now cut off, thanks to this winter blast from the past.
The robins will not starve to death, they will survive by switching to their lesser favourite food of frozen and mushy crab apples, or sumac seeds. And, being migratory, they have the option of turning around and flitting back south for a few days to perhaps Hamilton or Windsor.
Even the hardy ducks and geese will do a reverse flight if the waters began to freeze over again. While they seek vegetation and aquatic bugs in open shallow waters, they can adapt to the conditions by moving around, rather than staying put and hoping things will get better (this second option was tried by some earlier ancestors of these ducks ... and those genetic lines are no longer with us).
What I do worry about are the tree swallows and killdeer. These birds are notorious for returning in the first bit of sun and warmth only to be caught by a snowfall. The swallows eat insects, flying insects. These flying insects emerge when the sun’s warmth has triggered a metamorphic change within their bodies, but the warmth has to be sustained over a number of days.
When that first wave of swallows sweep in there may well be a few flying insects to be had. But once the snow hits, gone is the food source for these aerial feeding birds.
So they have options: sit on the ground and starve; do an about face and fly back south to where the insects are indeed abundant (that would be Tennessee or South Carolina); or find a hollow tree or nesting box and hide out inside with a few fellow travellers and just conserve energy and stay warm and dry for a few days.
The killdeer are ground nesters, depositing their eggs in a gravel depression; no insulating feathers or cattail fluff to line the nest, just pebbles. Cold pebbles. So one hopes that either the cold snap happens prior to egg laying, or is a short one- or two-day event.
The resiliency of a species depends on the toughness of its individuals. If enough of them can stay and wait for that flush of food that will appear, eventually, then those survivors get to pick the best nesting territory. While a few may indeed die, the tough (lucky?) individuals will carry that trait onwards in their DNA.
The resiliency of an ecosystem depends on the biodiversity of its inhabitants. By example, a wetland swamp has thousands of different species of plants, birds, mammals, invertebrates, reptiles, amphibians, lichens, mosses, and so forth. If one of those species had a bad start to the year (lack of warmth, lack of sun, lack of food, etc.), the others will survive and the ecosystem keeps functioning.
But if that particular swamp is in overall decline (due to being degraded of its biodiversity) and has a diminished occupancy of species, then bad times will descend upon that site.
All of this talk of resilience ties in with the larger topic of climate change ... can the native species adapt fast enough to keep pace with these human-influenced changes?
For each of the last 12,000 years, when the Wisconsin glacier began melting, all species have been pushing their limits of survival to be the first back, the first to nest, the first to bloom.
What doesn’t kill them may just make them stronger.
