How to Search for
Passerines More Effectively
in Winter:
Notes on Winter Habitat Microsites
(for pdf version click here)

David Irons and David Fix
From: Oregon Birds 16(4): 251-254

Have you ever noticed that there is one particular birder, or group of birders, who always finds the Orange-crowned Warblers on Christmas Bird Counts? What do they know about winter passerine birding that you may not?

The discussion which follows explores 2 elements of bird finding critical to a successful search for concentrations of brush-loving winter songbirds, and for the occasional rarities that linger among them:

   1. Identifying and locating good habitat, and

   2. Having located the habitat, knowing how to bird it most effectively.

An understanding of these points is guaranteed to make your winter birding more enjoyable. It will also make the search for unusual winter passerines far more fruitful.

Knowing how to identify quality habitat is the most important factor in finding winter passerines. The best sites occur almost universally at the edges of pastures, small farms, at the outskirts of residential areas, and in the brushy tideland margins about the heads of estuaries. Such unmanaged patches of land are characterized by a mixture of rank vegetation familiar to us all. Almost always present are Himalayan blackberry,grass of varying height and density, tall weeds, thickets or stringers of deciduous saplings, and teasel. Sites near slow-moving or standing water offer marsh vegetation such as bulrush, cattails, or canary grass.

Collectively, these unglamorous sites lack a short descriptive name. With increasing coverage of such places, it seems advisable to coin a label which will serve as more of a catch-all than "blackberry patch," "willow ditch," or "pasture edge thicket." Reflecting the spectrum of vegetation within these sites, and a blend of disdain and fondness, the loose conversational term "kack" has been used by the authors to describe such places. Although not a flattering handle the word does conjure up a mental image of lowland pockets of rank thickets ponds, and openings attractive to wintering sparrows, kinglets, warblers, and the like.

Call these places "winter microsites, "kack," "sparrow patches," or whatever, but recognize that they are the winter home for droves of Song, Fox, and Zonotrichia ("crowned") sparrows: Dark-eyed Juncos, Rufous-sided Towhees, and Ruby-crowned Kinglets. Lesser numbers of Bewick's Wrens, Winter Wrens, Black-capped Chickadees, Bushtits, House Finches, and Yellow-rumped Warblers use these sites. In southwestern Oregon,Hermit Thrushes and Wrentits are routinely found in such habitat. Black Phoebes also show a preference for those locations within their range in Oregon, especially in winter.

If you are an Oregon birder who encounters Lincoln's Sparrows only a few times each winter, you have not been visiting the lowland thickets which are heavily grown with teasel, scattered blackberry mounds, and clumps of grass. These situations are strongly favored by Lincoln's Sparrows. Birders working winter passerine microsites as a matter of course quickly come to appreciate the comparative abundance of these sparrows in choice habitat. The presence of numbers of Lincoln's Sparrows at a winter passerine microsite serves as a reliable index to those places offering good potential for a White-throated Sparrow and other uncommon winter birds.

The best indication of improved coverage of "kack" patches in Oregon has been the great increase in sightings of Swamp Sparrows. Although these birds inhabit extensive marshy areas as well as more closed-in places, their general habitat is the same: dense grassy, weedy, sapling-dotted boggy pockets, often with tangles of blackberry and some standing water. Swamp Sparrows are seldom encountered outside this type of habitat in Oregon.

Somewhere in Oregon each winter, a diligent birder who understands the promise of such sites discovers a Common Yellowthroat, a Nashville or Tennessee Warbler, a "westside" Loggerhead Shrike, an unusual fringillid, or some other mind-bending winter rarity. In most cases, these unseasonal or out-of-range birds owe their discovery to more than mere chance.

Why is such diversity supported by these sites?What causes them to stand apart from other habitats, to the extent they merit this discussion in Oregon Birds?

One can best examine this by looking at the factors allowing-or prohibiting- delicate passerines to overwinter in Oregon. What do the less hardy species require? As is true for any other group of birds, they need food and shelter. Good wintering habitat offers these necessities in a setting that minimizes energy expenditure and stress. A steady, varied, winter-long food supply within, or near, abundant protective cover is the best possible combination.

Thewinter microsites we have described meet these needs. They offer both seeds and insects. Their location in protected bottomlands and often near water allows for a reasonable winter insect fauna. Mounds of Himalayan blackberry create a thick, tangled, multi-stratified composite of vegetation harboring not only a seed supply, but conditions under which insects appear to remain numerous and active during the colder months. Blackberry thickets are also excellent cover for many species of passerines. If blackberry is not present, it is often replaced by teasel, or by agricultural waste such as grain stubble or rotting vegetables. The abundance of dead and living vegetation at these sites provide concentrated seed supplies and winter insect populations exceeding those in less varied, less fertile habitats.

By contrast, extensive parcels of monotypical habitat may offer either abundant food or abundant shelter, but seldom both. Consider the Douglas-fir forest (lots of cover, comparatively little food) or the corn stubble field (lots of food, no cover). A mix of food and shelter is an unbeatable combination. It supports wintering songbirds of a variety of species in high densities.

Note that the presence of composting vegetation, a manure pile, and/or water can create a particularly dynamic situation. Exceptionally temperate microsites are far more likely to prolong the survival of delicate or semi-hardy passerines than are surrounding areas of relatively low biological vigor. Many of the tropical-wintering passerines detected in Oregon in late fall and winter have been found at such sites. Driving home this point most vividly was the Blackburnian Warbler which overwintered at a composting manure pile near Nehalem from November 1987 to March 1988.

Where are such places found? They occur widely along the coast, in the Western Oregon valleys, and in lowlands east of the Cascades. One of the tricks to locating good sites is to try to think like a bird." Where would you go to find as rich a wintering area as possible within the general area? Where is the food, the shelter, the temperate microsite? Meanders of smaller waterways grown to dense thickets and grassy openings are promising locations, especially where they border small farms, community garden plots, and sewage ponds. Many of Oregon's sewage ponds offer good surrounding habitat for wintering passerines.

The second element to getting the most from these places involves birding them as efficiently as possible.

Although any active birder knows how to find birds, maximizing the promise of win ter passerine microsites demands standing where you can best see the birds. The use of "spishing" and imitations of Northern Pygmy-Owls to draw forth as many birds as possible, and simple patience.

The birds using these sites spend most of their time on or near the ground. Although a large assemblage of birds of many species may be present, only a few curious Song Sparrows may be readily seen. One of the things necessary to increase several Song Sparrows to 3 dozen birds of 10 species, is to get into a position allowing clear views of as much of the habitat as is practical. When working from the roadside, avoid peering over or through tall hedgerows. It is generally better to be in the open, a bit removed from the center of activity, rather than to attempt to view birds among dense screening vegetation.

To fully appreciate the abundance and variety of birds using these winter microsites, one must spish and "pygmy-owl" both constantly and loudly. Birders who do not spish and imitate pygmy-owls cannot hope to encounter the full effect of a mob of hysterical sparrows, kinglets, wrens, and warblers, bouncing about close at hand. The authors have found best results when one birder spishes while another does pygmy-owl imitations. Birders who have worked together will easily mix spishing with sets of pygmy-owl calls. By making attractant noises, one causes 2 important things to happen within the flock. First, birds which have been foraging in scattered fashion across the breadth of the site assemble near the observer. Second, they will take exposed perches nearby: in a sense, they want to see you as much as you want to see them.  Opinion varies on how loudly one should spish, with some birders taking the position that very loud noise causes some birds to become wary. However, there is an advantage to loud spishing; the farther the noise carries, the further away birds can hear it. A Swamp Sparrow fifty yards from the road may never be detected unless it can hear attractant noises and respond to them by flying nearer. Spishing and "pygmy-owling" are essential tools in the search for that rare winter straggler.

Patience is a virtue the birder learns through long experience.As with any concentration of birds, the longer one "pounds" a flock of passerines, the more birds one will see and hear. An extra five minutes' effort may result in only a few additional birds coming to one's attentionóbut among those latecomers may be the Orange-crowned Warbler or White-throated Sparrow hoped for upon arrival at the site.

A related point, too often disregarded, is that a single visit may not be suffcient to detect all of the birds using the site. This is especially true in the case of extremely large assemblages. The center of foraging activity may shift from hour to hour, day to day, such that only a portion of the entire scene may be obvious in a given visit. During the heyday of the great winter sparrow flock in Eugene's Alton Baker Park garden plots in the mid-1970s, it became obvious to birders working the site that perhaps 80 percent of the entire group might be viewed on a given day. For a birder determined to get the whole picture, 80 percent coverage is unsatisfactory coverage. For this reason one should expect to pay several visits to the big sparrow flocks, preferably spaced over a period of weeks.

Oregon Birds16(4): 251-254