I finally reserved a calm, semi-sunny day to do some birding and exploring around my new home in northwest Montana. The plan was to circumnavigate Flathead Lake and stop at a few of the 6 state parks, 9 fishing accesses, and a National Wildlife Refuge that ring this largest natural freshwater lake west of the Mississippi. My first stop was the Big Arm Unit of Flathead Lake State Park, on the west-central shore of the lake. This 217-acre park sits at 3,000 ft. elevation and offers a stunning view of Flathead Lake and the towering Mission Mountains to the east.
Big Arm supports a mixed ponderosa pine and Rocky Mountain juniper forest. This dry conifer forest type is common in lower elevations of the Rocky Mountains. Understory vegetation is perennial grasses with patches of western snowberry and wild rose.
As soon as I started my hike, I heard the distinctive high-pitched, single-note call of a Townsend’s Solitaire, a locally common thrush during fall and winter. I located the solitaire perched atop a juniper, but immediately noted several others calling and flitting about in my peripheral vision. I then heard a soft, sweet, warbling song from another juniper, eventually matched to an American Robin. I stopped to simply observe the hive of thrush activity around me. I was surrounded by a massive feeding congregation of solitaires, robins, and Cedar Waxwings — literally hundreds — gorging on the fall crop of ripe juniper berries.
I observed an obvious traffic pattern among the thrushes and waxwings. After a period of feeding, individual birds made short flights to the shoreline to drink and bathe, then returned to the junipers to resume feeding.
After an hour of watching thrushes and waxwings, I followed a path along the shoreline and entered a still, quiet patch of forest. From the northeast I heard some distant chickadee calls. Within moments, half a dozen bird species appeared around me, flitting among tree branches, scaling tree trunks, and hanging upside-down from twigs. I was in the middle of a mixed-species feeding flock of Black-capped Chickadees, nuthatches (Pygmy, Red-breasted, and White-breasted), Brown Creepers, and Downy and Hairy Woodpeckers!
Mixed-species feeding flocks are one of winter’s special gifts to birders. They can occur practically anywhere in North America – even in your own backyard. The advantages of this flocking behavior are thought to be twofold. One theory suggests that flocking increases the number of eyes and ears available to detect predators. In fact, available data suggest that flocking birds suffer relatively low predation risk because of the increased probability that an approaching predator will be detected.
A second theory suggests that feeding efficiency drives the formation of mixed-species flocks. Unlike individuals in single-species flocks, where all members are competing for the same food, birds in mixed flocks have different food preferences and foraging techniques, thus each individual faces less competition than it would in a flock of conspecifics. Flocks may also function to overwhelm territorial defenses, allowing them to feed through an area from which single birds would be ejected by the “owner” of the territory. In addition, having more individuals searching for food increases the likelihood that a rich feeding patch will be encountered.
Interestingly, mixed flocks are not communal organizations where responsibilities are fairly shared. Studies in North America show that mixed flocks are typically led by members of the Paridae family (tits, chickadees, and titmice). The parids serve as “nuclear” members of these flocks and do virtually all the communicating. Other “attendant” or “satellite” species — nuthatches, creepers, titmice, woodpeckers, kinglets, warblers — trail along, clued in to the highly vocal and social Paridae leaders, ready to respond to their predator alarms. By exploiting a free “lookout system” in the nuclear species, the sentinels are able to devote some of their energy normally expended on predator defense to foraging instead.
Observing mixed-species feeding flocks has been compared to “chasing tornadoes.” You don’t know when to expect them or where they’re headed, but when they do come through, you have to be ready to go! After spending my entire morning chasing the mixed-species flock at Big Arm State Park, I couldn’t agree more with this analogy. But it was one of the most exciting and enjoyable days of birding I’ve had in along time.
I’ll leave you with a few more photos from Big Arm and a Christmas wish that a mixed-species feeding flock graces your path this winter.
Happy Winter Solstice and a joyful Christmas and New Years to all!
What the flock is happening bird-wise in your world?