The Garden Bug: Winter warnings

By Brenda Weaver

If you make soft, repeated "psh-psh-psh" sounds while standing near trees, this is bird-speak for "a predator is coming near". Even in winter, some birds may investigate, and may also make a few short calls of their own to help warn of danger. The black-capped chickadee is often the first to respond; they are known to vary the rate or urgency of their calls to convey the distance of the threatening predator.

Source: northernwoodlands.org