Species on the move: Mountain Chickadee

Andrew Farnsworth The Cornell Lab Sep 25, 2020

Team BirdCast has received some reports from “friends and family in the field” about intriguing bird movements occurring in the Rockies and other portions of the western US. And this post was inspired by a brief discussion with Brandon Percival and Chris Wood, regarding exceptional numbers of Mountain Chickadees, Evening Grosbeaks, and Steller’s Jays in Pueblo, CO, as well as increasing numbers of Woodhouse’s Scrub-Jays, Pygmy Nuthatch, Williamson’s Sapsucker, and Cassin’s Finch.

At this point you have heard the stories for the west about bird mortality, but perhaps you have not heard the stories about species on the move out of the mountains. Whether there is some ultimate connection among the mortality events, migration phenology and characteristics in the region, and irrupting into lower elevation habitats, there are some interesting movements occurring now in many areas of the west. BirdCast will feature some of these evolving stories about these eruptions from higher elevations!

Mountain Chickadee

Mountain Chickadee is a common songbird of montane coniferous forests in many areas of western North America. Populations of this species occasionally stage irregular migratory movements from montane breeding areas to surrounding lower elevations (sometimes quite far from any mountains). These irruptive movements into lower elevation habitats are largely driven by resources, or a lack thereof at higher elevations. So far in 2020, observations are flowing in that suggest Mountain Chickadees are on the move. The animation below highlights eBird observations of the species over the last month. Our animation below shows reports of chickadees beginning in the last week of August 2020 (dark and medium purple dots, scaled in size by number of reported individuals). Notice that most reports are associated with mountainous areas, but even this early in the season some reports away from mountains appear. The first week in September see the species appear in similar distributions (medium blue), but notice that an increasing number of observations come from non-mountainous areas, a pattern that grows in the second week of September (light blue and teal), the third week of September (yellow-green), and finally into the fourth week of September (yellow).