Springtime out of tune

This column was published in the Cranbrook Daily Townsman Friday May 14, 2010.

Yellow bird, yellow moon
You've arrived while the spring is out of tune
- Justin Rutledge, from "Jack of Diamonds"
 

The un-spring like view of our driveway

I confess I've never heard Justin Rutledge's music, but a review of one of his concerts included this lyric. Though out of context for a late-season snowfall, it seemed fitting for recent East Kootenay weather. A week ago our spring was badly out of tune.

Quite a difference a week can make. Last Friday we awoke to a winter wonderland with Christmas carols the most appropriate lyrics. Pretty enough, I suppose, but winter weather occurring during winter (where was this snow in February?) seems a better idea.

So what happens to the yellow birds and when they arrive from their tropical winter paradise only to find that spring is "out of tune"? We don't find piles of dead birds under trees, so how are they able to cope with such weather anomalies?

The unfortunate answer is that some don't. Late cold snaps (or early autumn ones like last year's Thanksgiving weekend's -15°C) take their toll on wildlife, particularly pint-sized songbirds. However, most adults are able to withstand brief periods of unseasonable cold.

That the cold and snow occurred before most species had young in their nests is very helpful in avoiding widespread mortality. There may have been some egg failure among early nesting species such as robins, but snow at the end of May it is far more damaging.
 

Most songbird nests are highly exposed to the elements and baby birds, often still featherless, are very susceptible to cold, snow and heavy rain. Cool springs or one freak storm can wipe out a large percentage of a year's songbird production across many species. Some may lay a second clutch of eggs, but many pack it in and wait for another year.
 

Hummingbirds, having returned for the summer nesting season, instead met with a big white surprise. But the physiological adaptations of these tiny marvels are astounding. Their small body size and highly active lifestyle means they have incredible energy demands which would otherwise leave them vulnerable to cold temperatures. However, the advantage of small body size is that warming up and cooling down are easy and efficient. Even most nights in summer, they slip into a torpor of slowed metabolism and lowered body temperature. Normal temperature for most birds, including hummingbirds, is in the 40ºC range. But in torpor, that can drop close to below 15ºC. The advantage is that their metabolic energy demands drop by 50%.

In fact, the greatest danger to endotherms (animals which can regulate their internal temperature - birds and mammals) is overheating. Normal body temperature is very close to the point of irreversible cellular damage. Living on the edge like this may seem dangerous, but speeds metabolism and movement of nutrients across membranes as well as optimizing nerve transmissions. Maintaining a high brain temperature may also assist in learning and memory.
 

Many so-called cold-blooded animals (more properly termed ectotherms) rely on behavioural adaptations to survive the cold and snow. Snakes just emerging from their underground winter hibernation sites will quickly retreat to their subterranean warmth. Frogs either stay submerged in water or seek refuge under forest floor leaf litter and rely on their ability to withstand some freezing.
 

So while spring may occasionally be "out of tune", it's certainly not entirely out of character. And as for the older song that waxes poetic about "Springtime in the Rockies", I doubt the author ever spent many springs in the mountains. It can be the cruelest of seasons.