Winter 2006

Table of Contents

Black-capped chickadee.

Winter feeding station visitors change

The chickadee at your winter feeder today is not necessarily the same one you enjoyed watching when you started filling the feeder last fall.

There are often large change-overs in individual birds at winter feeders, with immigrants far outnumbering year-round residents. Short stays at any one feeder are more common than not, with few birds coming back week after week.

Some birds you see now may be year-round residents that choose to stick around, but many more are likely migrants from areas farther north or higher altitudes that are moving as food sources become scarce.

Some species have “partial migration,” where some individuals migrate but others do not. Age and sex sometimes make the difference. Juveniles often migrate while adults stay. Many winter immigrants to our area are younger birds. Sometimes females migrate and males remain.

Periodic migrations or “irruptions” also occur. All of a sudden a mass of birds shows up in our area when normally they would have remained in Alaska or Canada. Evening grosbeaks, purple finches, pine siskins, snowy owls and rough-legged hawks are among the species that “irrupt” here. These mass southward movements are largely food based, sometimes combined with high population numbers.

For example, there may be a higher-than-normal population of evening grosbeaks in the north, combined with a failure of spruce and pine seed crops. Evenings grosbeaks must move south to find the necessary food available from our conifers, or bird feeders.