September — 2008

Monday 1 — Saturday 6

Alpine Avens turns the tundra red; Common Sunflowers scorch the plains with brilliant yellow.

Frost becomes a nightly affair in the high country.

First snows dust the high peaks.

Elk bugling becomes more regular.

Sunday 7 — Saturday 13

Migrating hawks bound for South America form kettles over the plains. Kettle size varies from less than 10 to several hundred hawks. Most kettles will be entirely Swainson’s Hawks, but kettles of Broad-winged Hawks occasionally pass through. Individual Northern Harriers, Cooper’s Hawks, and Red-tailed Hawks may temporarily mix with Swainson’s. Watch for gulls to work the same updrafts with the hawks.

Sabine’s Gulls begin passing through in small numbers. Some keep going; some loiter for days or even weeks.

Sunday 14 — Saturday 20

Quaking Aspens reach their finest color, peaking slightly earlier in extreme northern Colorado and a few days to a week later in extreme southern Colorado.

Snows falling at high elevation linger and do not entirely melt.

Pronghorns segregate into groups dominated by a single buck as their breeding season gets underway.

Sunday 21 — Tuesday 30

Moose begin taking each other more seriously. Listen for their low, throaty grunting.