Birding at this time of year can be slow at times, but at other times it just hopping. An interesting phenomenon that occurs in the post-breeding season is the formation of loose feeding flocks of various species. Most of these are migratory birds that will be leaving soon, but some of the residents get involved too. These flocks occur most commonly in the last week or two of August and sometimes into early September. It seem that they may also be at least partially weather dependent. This year I saw only small groups, but in the past I have seen some remarkable flocks. A couple of years ago, while standing on my back deck for 20 minutes, I noted a flock of 30-35 birds that included16 different species.
The most common species in that group was the Yellow-rumped Warbler. There were at least 10, including a couple of young birds still being fed by parents. This species commonly flocks together prior to, and during migration. All other species were represented by just one or two birds. Other warblers in the group were Townsend’s Warbler, Yellow Warbler, Wilson’s Warbler, American Redstart and Orange-crowned Warbler. Townsend’s and Wilson’s Warblers do not breed in the valley bottom so these birds have already left the breeding grounds. They may have moved in from the north or perhaps just dropped down from higher elevations.
There were three species of vireos in the group: Cassin’s, Red-eyed and Warbling. All three of these breed in the area so they may have been birds that were around all summer. Warblers and vireos find most of their food in the foliage of deciduous trees. As I watched the flock, these two groups were seen repeatedly taking insects or larvae from the birch leaves. Warblers are a little more agile and they could be seen fluttering beside the leaves as they picked off the food items. Vireos would generally stay perched on the branch as they retrieved their food items.
The group contained two different flycatchers; Hammond’s Flycatcher and Western Wood Pewee. These species also eat insects, but they catch theirs in mid-air. They perch on a branch that gives them a good view of their surroundings and wait for something to fly by. When it does, they give chase and catch it in the air, often with an audible snap to the beak.
Other species in the group included Western Tanager, American Robin, Black-capped Chickadee, Red-breasted Nuthatch and Cedar Waxwing. If you should notice bird activity in your yard, have a close look. You may be pleasantly surprised to find that there are more birds than you initially thought, and you may be surprised at the species diversity.