Waiting For Waxwings

Day 291: Many plants and animals and undergoing phenologic shifts due to the changing climate, and because some are drifting toward earlier seasons and others to later ones, this can be critical. We are seeing wildflower blooms before the arrival of species-specific pollinators, with the consequence that the wildflower species do not set seed and the pollinators go hungry if they cannot adapt to other food sources (and many are not biologically equipped to do so). Another glaring example of radical phenologic divergence is taking place right in my own yard. For the last several years, the fruits on my Sitka Mountain-ash (Sorbus sitchensis) have been ripening earlier and earlier. Now almost a month ahead of its original period, the fruit is colouring while the Cedar Waxwings (Bombycilla cedrorum) are still far to the north where food is plentiful. At the same time, the Waxwings have been arriving here later and later, and last year, the berries had already begun to fall from the Mountain-ash before they showed up in late October. This native tree is one of their primary food sources during the autumn migration. If the berries are gone when the Waxwings arrive, many will not survive their southward journey. In the long term, this may lead to a change in the Waxwings' range, extending it northward and reducing it to the south. However, the operative word in the last sentence is "may." If the Waxwings and Sitka Mountain-ash fail to perform in parallel, one or both may not survive as species.