Nature is full of finely twined inter-relationships and dependencies – wolves and moose, figs and fig wasps, middle-aged men and Tim Horton’s coffee. No one living thing can stand alone. I was reminded of this when I came upon a Ruffed Grouse feeding high in an Aspen Tree near West Branch, Michigan. The rotund bird was plucking the emerging flower catkins off the twigs as if they were berries. One cannot cite a better example of interdepency than that between the Ruffed Grouse and the Quaking Aspen. The two populations perform a sort of dance.
Ruffed Grouse, or partridge as they are known in these parts, are primarily ground dwelling fowl. They are, after all, camouflaged in order to blend into the forest floor. As chicks, they feed heavily on protein-rich insects but soon lock into a regimen of plant food ranging from hazelnut, birch, and willow catkins to acorns. Aspens, however, are the single most important year round food for Ruffed Grouse. They feed on the winter buds, spring flowers, and even the leaves.
This Aspen affinity necessitates regular flights up to lofty twiggy perches. Admittedly grouse look rather awkward when so engaged – especially during winter and early spring – and are exposed to attacks by large birds of prey such as Goshawks. It is a benefit to their overall health to eat quickly and researchers have determined that a prompt partridge can fill its crop in as little as 15 minutes. Once filled, the birds glide back down into dense cover and digest their meal in cryptically-colored peace.
Not all Aspen trees are equal in the eyes of a springtime Ruffed Grouse. Only staminate trees, or male trees, are patronized by Ruffed Grouse. Like other members of the popular family, individual trees are either male or female. April is flowering time for Quaking Aspen and the fuzzy masculine flowers are called Catkins (just thought you’d like to know that for some reason).
Add to this the fact that not all male Aspens are grouse-equal either. Not only do the grouse prefer older trees but, for some reason, only certain individual trees are considered worthy of their patronage. They will consistently feed at one tree while totally ignoring the one next to it. According to those same researchers who determined the crop-filling time mentioned earlier one mature male Aspen can provide enough food to satisfy a single grouse for 8-9 days. So, why ignore a perfectly good Aspen? The answer, my friend, is chemistry (isn’t it always!).
Let’s be brief about this thing. Buds and flowers from grouse feeding trees have more protein content than those ignored by the birds. They also contain lower levels of a nasty sounding chemical called coniferal benzoate. In short, the grouse know a good flower when they taste it. Good taste translates into high nutrition value. If you are going to expose yourself to danger you might as well eat the good stuff. None out of ten Goshawks also agree that the best tasting grouse come from the best quality Aspens.
The mystery – the dance element, if you were – is that grouse populations fluctuate on a regular basis. They are on a short 10 year cycle within a longer 20 year cycle. Although amusing sounding, it is serious scientific geek-speak to say that there are low-low years, high-high years, low-high years, and high-low years! The cycle within a cycle phenomenon has absolutely nothing to do with Al Gore or bad human planet-bashing humans. It seems that the Aspens are partly responsible for this, because in some years they are in-edible and shift their chemical allegiances. There are good and bad (as well as bad-bad, good-bad etc.) years for aspens and good and bad years for Grouse. This up and down grouse also translates to the grouse predators as well.
As a way to fully involve myself in this discussion, I decided to try a taste test. What’s good for the grouse is good for the naturalist, I sez to me-self. So, I selected a male flower from a fine-looking male specimen of Quaking Aspen, bit into it, chewed it, and the result was a bad-bad grouse face (see reaction shot here). Apparently my sample was one of those high coniferal benzoate types which tasted like a pine cone cooked in turpentine – in other words fit for a Martini drinker. I will need to develop my grouse senses further if I am to pursue this line of foraging.