Wood Thrush

The wood thrush, found in forest interior habitat, is a charismatic and captivating forest bird. Mornings met with a wood thrush’s cheery and mystical song make any birder feel familiar in that forested environment. With an impressive vocal repertoire, from its unforgettable “ee-o-lay” to its more obscure pit volleys, which are a sharp series of notes—when a wood thrush is in a  woods and it’s singing, it’s unmistakable.

Over the past 50 years wood thrushes have experienced significant declines of at least 60% of their population. Some research shows that wood thrushes overwintering in drier Mexican forest fared worse on breeding grounds, due to the droughty conditions and apparent lack of food availability. When those birds returned to North America to breed, they were in rough shape and laid fewer eggs or couldn’t care for the eggs they did lay. While destruction and fragmentation of forests in Central America certainly doesn’t help wood thrushes, it’s been found recently that fragmentation in North America might be the leading cause of population declines. Wood thrushes need large mature forest in order to breed, while constant disturbance in these forests may not benefit wood thrushes.

The oak and hickory woods at Faville Grove Sanctuary. Photo by Madison Audubon.

At Faville Grove, wood thrushes are uncommon in our mostly grassland landscape. However, nearby oak woodlands, lowland forests along the Crawfish River, and certain Tamarack swamps may hold a few birds. We’ve been hearing them more frequently with the interns in the past couple of weeks. Research shows that post-fledgling birds prefer to hang out in dense shrub thickets on the edge of forested habitat, likely for protection from predators and increasing availability of fruits and invertebrates. That post-fledgling movement may explain why we’ve been hearing them more recently around some grassland and shrubland areas. You should look and listen for this bird near larger forested tracks at Faville Grove.

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Kelly Colgan Azar / Flickr Creative Commons

Breeding Bird Distributions

Bird distributions are not random. Across the state, one notices that loons are a distinctly northern Wisconsin species, or that yellow-bellied sapsuckers occur over the northern half of the state, while also extending into western Wisconsin’s Driftless Area. Perhaps even locally, one notices an abundance of Canada Geese breeding around urban ponds, where park lawns and predator-free expanses make happy geese. 

Color codes for breeding status.

Of peculiar interest to me, at Faville Grove Sanctuary, is the presence and absence of certain bird species. Today, we will observe the biogeography of certain bird species in Wisconsin, based on maps pulled from eBird data on the second Wisconsin Breeding Bird Atlas. To the right, you’ll see the different categories of breeding, based on quantitative observations gathered during Wisconsin’s recently completed five year long Breeding Bird Atlas.

The striking feature of many of the maps that follow is the absence of breeding birds in the Faville Grove Area. From roughly Lake Koshkonong to south, Madison to the west, Horicon Marsh to the north, and the Kettle Moraine to the east, one notices distinct range gaps in many of these bird species. The absence of certain species in this region speaks to the necessity of a landscape-scale habitat project, and the presence of many of these birds at Faville Grove is a testament to the habitat restoration conducted here. 

A fun game is to try and guess the species based on the map.

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First, we will analyze the upland sandpiper. Formerly abundant at Faville Grove, the bird used to nest with up to one pair every 1.5 acres, though the birds have not been seen in decades. Art Hawkins, one of Aldo Leopold’s graduate students, published an important paper on the ecology of the Upland Sandpiper at Faville Grove. 

The bird occurs south, west, east, and north of Faville Grove, though in very small numbers. South of Baraboo you can see a block of confirmations from the Sauk Prairie Recreation Area, which includes large acres of new prairie restorations. With new land acquisitions at Faville Grove forming large contiguous blocks of prairie, we eagerly await a possible return of the upland sandpiper.

Upland sandpiper, photo by Vitalii Khustochka, FCC

Upland Sandpiper breeding range in southern Wisconsin, conspicuously absent from the circled area. Star indicates Faville Grove Sanctuary

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The short-eared owl was a common breeding species at Faville Grove up until Aldo Leopold’s time in the 1930’s and 40’s. The bird has returned with increasing grassland acreage, overwintering on a diet of meadow voles from the prairie. There is potential for breeding pairs with expanded contiguous habitat.

Short-eared owl, photo by Mick Thompson

The light purple block west of the I-94 marker is the atlas block that contains Faville Grove Sanctuary

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A charismatic and bold bird, the red-headed woodpecker is a relatively common breeder in southern Wisconsin, though remains uncommon in the Faville Grove region. Oak trees and dead snags are critical to keep this species over summer, and a breeding pair has occupied this exact habitat at Hope Lake Bog (an outlying Madison Audubon property) for a number of years. Consistent sightings in the savanna of the Lake Mills Ledge indicate that the canopy thinning has improved habitat for this species.

Red-headed woodpeckers, photo by Kelly Colgan Azar

Red-headed woodpecker breeding locations.

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A unique warbler with a warm buzzy song, the blue-winged warbler has been expanding northward in Wisconsin since the turn of the twentieth century. Between the first and second Breeding Bird Atlas, breeding pairs have moved even further north into the northwestern and northeastern parts of the state. Yet, the bird is strikingly absent from the Faville Grove Area. One pair was confirmed during the Atlas at the Waterloo Wildlife Area, to the north, where I have seen and heard dozens of the birds during migration. Nesting in shrubby areas and along forest edge, why the birds remain absent from Faville Grove remains a mystery.

Blue-winged warbler, photo by Kelly Colgan Azar

Breeding map for blue-winged warblers in southeastern Wisconsin.

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A declining forest bird, the ovenbird lacks necessary habitat at Faville Grove. A ground nester, the ovenbird needs extensive forest tracts.  From the map, we can almost identify the entire Kettle Moraine from southwest to northeast. It seems that outside of the Kettle Moraine, little suitable habitat exists. This is a common plight of many forest birds—the southeast glacial plains ecological landscape is about 4.9 million acres, with almost 3 million acres in agriculture. A mere 392,000 acres of the entire landscape is upland forest, and the only large blocks of forest are located in the Kettle Moraine, where you can also find ovenbirds.

Ovenbird, photo by Kelly Colgan Azar

Breeding map for ovenbirds in southeastern Wisconsin.

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Found in young forests and shrublands, the mourning warbler occurs for the most part north of Faville Grove, but does breed in the Southern Kettle Moraine State Forest. Savanna restorations may be important breeding areas for this bird, though the overall extensive forest cover of northern Wisconsin is preferred.

Mourning warbler, photo by Tom Benson

Breeding map for mourning warblers in southeastern Wisconsin.

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Here, we see a grassland species with an affinity for forb-rich prairies and high diversity. Faville Grove’s high diversity prairie restorations should provide excellent habitat for the grasshopper sparrow, and one singing bird this past summer could be an indication of a bright future at Faville Grove. Breeding pairs in this area would be an important population boost for the region.

Grasshopper sparrow, photo by Kelly Colgan Azar

Breeding map for grasshopper sparrows in southeastern Wisconsin.

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Finally, we can locate Faville Grove’s block precisely on this map, where a black square west of the I-94 marker confirms the breeding of Henslow’s sparrows at Faville Grove. Unburned prairie seems a necessity for the Henslow’s sparrow, and a shifting patchwork of burns has provided excellent habitat for an increasing population of this state-threatened bird at Faville Grove.

Henslow’s sparrow, photo by JanetandPhil, FCC

Breeding map for Henslow’s sparrow in southeastern Wisconsin.

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It could be that the geographic gap in species’ ranges is an artifact of the sampling—located between high population centers in Madison and Milwaukee, the gap apparent in many ranges could just lack sufficient birding. However, the map below shows many areas between Madison and Milwaukee with over 100 checklists, and an overall good coverage of the entirety of southeast Wisconsin.

Map of sampling effort in southeastern Wisconsin.

A confluence of factors merges to produce these range gaps in many species. As stated earlier, only 8% of the southeast glacial plains is upland forest. Of the entire landscape, only 4% is publicly owned. Small slivers of habitat tend to hold fewer birds than large blocks. Thus, on a landscape wanting for many bird species, a landscape-scale habitat restoration project like Faville Grove can fill the gap.

Written by Drew Harry, Faville Grove Sanctuary land steward

Ruffed Grouse

Wisconsin hosts many of the finest capitals of the world. Waunaukee is the only Wanaukee in the world. Mercer is the loon capital of the world. Racine is the kringle capital of the word. Milwaukee is the beer capital of the world. Boulder Junction, Stockbridge, and Presque Isle? The musky, sturgeon, and walleye capitals of the world. Bonus points if you can guess what Park Falls, Wisconsin claims as its capital of the world.

Ruffed grouse would be the answer. And if you're looking for reasons why Park Falls might hold so many grouse, look no further than the elegant aspen tree. Characteristic of the ruffed grouse is its iconic drumming, where breeding males display for nearby females. Males choose to drum in young and regenerating stands of aspen. They especially love trees aged 6-15 years, with an open understory, likely better for displaying purposes. Aspen, when cut, readily resprouts, often sending off thousands of shoots from its complex root system. Grouse prefer areas with about 10,000 woody stems per acre, a  massive clone of aspen! It may seem, then, that grouse need clearcut areas of regenerating aspen, but they prefer a more complicated arrangement than a simple clearcut.

A ruffed grouse perches in an aspen tree. Photo by Michael Klotz

As a non-migratory bird, grouse need enough resources to overwinter in a cold climate. Unlike blue jays which cache acorns, or woodpeckers which dine on bug buffets in rotting trees, grouse rely on a largely vegetarian diet of twigs, leaves, fruits, acorns, and buds. Thus, in order to overwinter successfully, grouse need access to mature trees which provide male flower buds. Small tree harvests of about five acres within a forest matrix yield excellent grouse habitat, according to research conducted in Wisconsin. Approximately three mature trees per acre in a clearcut can provide enough food resources for overwintering grouse.

The population dynamics of ruffed grouse obviously depend upon their habitat and food source, but there are higher effects concerning the grouse. Aspen is a short-lived species and cannot reproduce in its own shade, thus becoming quickly replaced by other tree species. The forest then shifts from early successional and young aspen sprouts to a less dense forest filled with larger diameter trees. While this situation may benefit many forest species like black-throated green warblers or pine martens, it is detrimental to the ruffed grouse because they need the dense cover of thousands of aspen sprouts to hide from predators. This forest succession has been occurring in northern Wisconsin for many decades, and grouse habitat and populations have decreased as Wisconsin forests have aged.

Ruffed grouse drums in the woods. Photo by Claudine Lamothe

Predators also influence population numbers. Goshawks and great horned owls will prey on ruffed grouse in lean snowshoe hare years, and these predators contribute to a cyclical decline in the grouse population. That cyclic nature of ruffed grouse populations is an interesting phenomenon. Due to DNR surveys conducted by wildlife professionals and volunteers, Wisconsin has grouse survey numbers for every year since 1964. You can find that information and the Wisconsin Department of Natural Resource's most recent report here. According to these drumming surveys, populations spike every ten years or so, almost always in a year ending in 9, 0, or 1.

According to statewide numbers from this survey, 2017 saw an increasing population, setting the stage for a climb to a peak in 2019, 2020, or 2021. However, 2018's survey found a rather sharp decline on these drumming routes. As of yet, it's unclear what caused this decline.

A ruffed grouse struts through a woodland with oak leaves and moss covering the ground. Photo by Tim Lenz

Today, ruffed grouse can be found in most of Wisconsin with the exception of the southeastern portion of the state. Faville Grove Sanctuary lacks ruffed grouse but they did historically occur here. Art Hawkins, a graduate student of Aldo Leopold, published “A Wildlife History of Favile Grove” in 1940 and according to his research and interviews with the previous generation, ruffed grouse were common in 1838. By the winter of 1936-37 the last “wandering” ruffed grouse was seen leaving Faville Grove, not to be seen again.

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Nicole Beaulac

Cedar Waxwing

This medium-sized marauder pillages from a variety of sources, all with one commonality: hackberries, winterberries, nannyberries, elderberries, black cherries, serviceberries, strawberries, raspberries, blackberries. Berries!

Of course, one of the most important berries in the diet of this bird is the juniper berry, from cedar trees. Cedar waxwings flock to these trees in winter. The two burly cedars in front of my house on Prairie Lane provide winter supplies to hungry waxwings and robins, but the tree also has its own interests at heart; juniper berries that have been ingested by waxwings germinate at a much higher rate than those that haven't passed through the bird, and 1.5-3.5 times as many of those seeds will germinate.

Cedar waxwing, photo by Kelly Colgan Azar

A frugivore, the diet of the cedar waxwing provides fascinating insight into seed dispersal and phenology. For instance, one study of waxwing diets analyzed their relationship with highbush cranberry, a native shrub. The red berries of this bush almost always remain on the bush through winter, and researchers supposed the waxwings consumed these fruits in April and May the next year because of higher sugar concentrations. However, when captive waxwings were given a choice between the fresher winter berries and next year's sugar-concentrated berries, the birds almost always chose the winter berries.

From this same research, observations in the field indicated that waxwings that consumed highbush cranberry in April or May complemented this meal with catkin pollen from cottonwood trees. In the lab, diets of cranberry or catkin alone caused the waxwings to lose mass, while a combination diet saw a gain in body mass. While the cranberry presents a rich source of carbohydrates, the cottonwood pollen offers high protein.

Highbush cranberry, photo by Barbara Gail Lewis, FCC

With a diet of only cranberry, waxwings saw nitrogen losses in their diets; secondary compounds in the cranberry make it very acidic, and in order to process this acidity waxwings had to catabolize protein to produce a bicarbonate buffer, according to researchers. The protein from the pollen offset these losses.

All of this is to say that the waxwings eat a well-balanced diet. While their dietary choices may seem like the whims of the flock, the menu of a cedar waxwing has important ecological implications for seed dispersal and for the bird's overall health.

In addition, berries amount to a sort of social currency in cedar waxwings. These birds exhibit delayed plumage maturation, where the tips of their secondaries turn a waxy red color. The length and vibrancy of this color is diet-related—waxwings consuming the invasive honeysuckle (with an orange berry) will develop orange tips. In a study of the reproductive success of waxwings, it was discovered that males and females with similar tips would mate. Those pairs with longer tips nested earlier and had larger broods and fledged more young than those pairs that were younger, with shorter waxy tips.

This is a bird that revolves around berries. From overall health to seed dispersal throughout the ecosystem to social status, berries make the bird, and the birds certainly help disperse the trees and shrubs that make the berries. You can find these interesting flocks at Faville Grove around any fruiting trees and shrubs.

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Kelly Colgan Azar

Hooded Warbler

Searching for this bird for the better part of the summer, I had more or less given up hope of seeing it this year. A denizen of the forest interior, the bird is on the far northwestern edge of its range in Wisconsin, and has never been recorded in Faville Grove Sanctuary, but manages to find breeding habitat in a few extensive southeastern Wisconsin woodlands. Glorious in its breeding plumage, the colors might light up the forest understory brush habitat where it occurs; but I wouldn't know as I haven't seen the species.

That is, until a few weeks ago when I stumbled upon a hooded warbler on a field trip with our summer interns. As a part of the 12-week internship, we take educational field trips to State Natural Areas and other sites where they learn from land managers about ecological restoration. This particular morning found us in a bog in the Kettle Moraine surrounded by oak forest, a spot where hooded warblers had been documented earlier in the year. However, I wasn't hopeful we'd find one as it was early August and the birds were likely to be quiet, especially given that it was already 9am on a hot day. We stumbled through the forest, eventually finding the bog and only hearing an eastern wood pewee, blue jay, eastern towhees, and robins. It was a quiet morning.  

On our walk back to the truck, the interns started to run down the hills along the trail, which ran perpendicular to the moraines so characteristic of the area.  As I neared the truck I stopped and listened for a moment and my ears perked up to hear the song of what I presumed to be a hooded warbler. Binoculars from a dozen different vantage points did not yield any conclusive evidence, and soon the bird stopped singing. About 75% sure that this was a hooded warbler, I was unsatisfied. On my phone, I clicked my volume as low as it could go and played an audio recording of a hooded warbler. Okay, now I was about 90% sure this was indeed a hooded warbler. One second later, I was 100% certain this was a hooded warbler as the bird flashed in front of my face and landed on a nearby shrub, tilting its head curiously at me. The bird stayed for a good few minutes, and I got excellent views of its brilliant black hood, yellow face, and olive upper parts.

Photo by Gary Leavens

As the bird lost interest in this man in a blue t-shirt curiously speaking hooded warbler, it entertained us as it flared its tail and hunted for insects. Just as soon was it gone, but what a wonderful few minutes of birding.

The habitat of the bird we found is typical of where one might find the species in southern Wisconsin. As part of the extensive forests of the Kettle Moraine, this bird was occupying a mostly contiguous block of forest about 280 acres in size. Research in Wisconsin has shown that forest blocks of 250-1,400 acres are necessary for hooded warblers to successfully breed.

Hooded warbler nest, photo by Richard Bonnett

Within that forested area, hooded warblers actually seek out opening in the forest canopy; areas filled with dense shrubs like wild plum, blackberry, raspberry, and grapevine provide excellent cover. Nest placement occurs within these shrubs usually from knee to waist height on a human.

Thus, some stand thinning and management can stimulate the more open sites where this species breeds. Indeed, where I found this recent hooded warbler, there were dead oak trees with an understory of brambles, grapevine, buckthorn, and honeysuckle.

It's unlikely that these birds might breed at Faville Grove Sanctuary, but some areas in Faville Woods have the structural characteristics that hooded warblers look for. Nearby areas would likely need to gain forest cover in order for that to happen. It's possible to see these birds in migration, and they should be on the move at about this time, continuing through the middle of September. They tend to migrate through dense forest patches with openings, much like their breeding preference.

Another treasure this bird left me with was an appreciation for the beauty of many of the common birds around the sanctuary. The hooded warbler looks similar to another warbler—the common yellowthroat—but the brilliant colors of the yellowthroat are taken for granted due to its abundance. What beautiful birds, each in their own right.

Hooded warbler, photo by Andy Reago & Chrissy McClarren

Common yellowthroat, photo by Kelly Colgan Azar

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Dave Inman