If you are prone to looking up as you walk (or pedal or drive) among trees, you may have noticed a bumper crop of cones clinging to the highest branches
If you feed the birds during the winter, you may notice some differences in the species visiting the feeders from year to year. Some species, such as chickadees, are consistent visitors. But other species, such as siskins, seem to vary considerably and during some years they seem to show up en masse, indicating some sort of invasion or "irruption" meaning a sudden change in the population density.