Nature Watch: Birds of Different Feathers
About the author: Steve Ellis is a naturalist and Land Trust member who enjoys sharing his love of the natural world. His blog series, “Nature Watch,” will appear each month in “Habitchat,” chronicling native plants and wildlife you can expect to see during that particular time of year. We thank Steve for sharing his passion, illustrating the importance of island conservation.
You’re walking a trail through a forest seemingly devoid of animal life. Suddenly every tree seems to have birds sifting through its branches. You’ve just encountered a mixed flock.
These congregations of birds start coming together in September. Diminutive Golden-crowned Kinglets and Chestnut-backed Chickadees form the mixed flock core. Black-capped Chickadees, Red-breasted Nuthatches, Brown Creepers and Downy Woodpeckers join in. Sometimes Bushtits and Dark-eyed Juncos add their numbers to the group. It pays to observe each member of the flock; individuals from species such as Cassin’s Vireo or Townsend’s Warbler may also tag along with these roving bands.
Mixed flocks are noisy, as their members call frequently to one another. The sounds and bustle of multiple birds moving energetically about often draw out species that prefer remaining hidden in cover. Hutton’s Vireos and Bewick’s Wrens may pop into the open to see what’s creating the fuss.
Mixed flocks may include hundreds of individual birds. They band together to increase the number of eyes that are searching for food and watching out for predators.
Advantages of traveling together are many. Areas already exploited and thus barren of food are avoided. Commotion from many birds moving about drives insects and invertebrates from cover, making them easier targets. Multiple members of the flock will be casting wary eyes for predators, increasing the time individual birds spend in worry-free foraging.
Large flocks of different species can be found in other habitats, too.
Often a mix of seabirds come together on the ocean’s surface. Auklets, cormorants, gulls and mergansers gather for feeding frenzies on schools of small fish. These formations are usually temporary in nature and will dissipate when the prey flees. The seabirds don’t travel together as do the mixed flocks of the forest.
Shorebirds of several species congregate on mudflats to feed. As with the forest dwellers, they rely on early warnings of approaching avian predators such as falcons. Flocks of Black Turnstones – a small shorebird found on rocky beaches – usually include a handful of Surfbirds and sometimes a Rock Sandpiper.
Mixed flock numbers peak in November with the arrival of birds from the north and those drifting down from the mountains. By spring, the flocks begin to come apart as birds pair up and peel off for the breeding season. Until then, these roving bands are proof that birds of different feathers do indeed flock together.
Fauna: Chestnut-backed Chickadee (Poecile rufescens)
These energetic birds are a mainstay of fall and winter mixed flocks. Common year-round, the populations are augmented with winter migrants out of the lower slopes of the North Cascades mountains.
Chestnut-backed Chickadees are smaller than their Black-capped cousins, measuring 4.5 to 5 inches in length. The head and throat are dark, contrasting with the white cheeks. Their name is derived from the chestnut-brown color found on the back and flanks. A white belly and gray wings and tail round out the field marks.
You may hear their high-pitched chick-zee-zee calls or the more abrupt chek-chek as they flit from branch to branch.
Spring finds them nesting in a cavity of a snag or deciduous tree. They rely heavily on holes carved out by Downy Woodpeckers. Five to nine eggs are laid in a nest constructed of moss, plant down and feathers. (A pair we hosted in a nest box used insulation extracted from a nearby pump house.) Fledging takes about two weeks.
Chestnut-backed Chickadees glean insects from foliage and bark, often feeding at the very tips of branches. Also on the menu are the seeds of conifers, especially those of western hemlocks, Douglas-fir, and western red cedar. They will visit your birdfeeders for sunflower seeds and suet.
The habitats for this iconic species are conifer or mixed forests. They’re one of the easiest species to entice into a nest box. The box should have a 1- to 1.5-inch hole and be situated 6 to 15 feet high. Place the box where there are trees close behind it; this allows the parents a chance to land on a nearby branch and survey the scene before entering the box.
Flora: Western Hemlock (Tsuga heterophylla)
Western hemlocks, with their characteristic droopy tops, are a nearly ubiquitous feature in many of our local forests.
These stately trees can grow to a height of 180 feet. The bark is grayish to red-brown, thin in young trees, and becoming thick and furrowed with age. Hemlock needles on a twig alternate between .5 and 1 inch (the species name means different leaves).
The cones of the hemlock are also little, measuring about an inch in length. Each holds 30-40 tiny seeds that are dispersed by the wind. The seeds are so small that it takes 300,000 to weigh a pound!
Douglas-fir is the hemlock’s chief competitor for space on the forest floor. The latter grow slowly and don’t have the longevity of Douglas-fir. They do, however, have adaptations that make up for that lack. Western hemlocks produce large numbers of seeds, ensuring new generations of trees. And unlike the Doug-firs, they can take root in rotted logs or atop stumps. A straight row of hemlocks that are the same age is proof the seeds germinated on a fallen log.
There’s one more trick up the hemlock’s sleeve. Douglas-fir must grow in sun, while hemlocks can thrive in shade. Over time these adaptations favor hemlocks, making them the dominant species in many lowland forests.
Several bird species forage for insects among the foliage or on the bark of hemlocks. The tiny seeds are eaten by small birds, chipmunks and deer mice. Robins and other birds nest and roost in the drooping, sheltering branches.
Western hemlocks can be found in many local forests, doing best on moist sites.