warbler

Tennessee Warbler

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The Tennessee Warbler flies through a Midwestern spring, making itself known with its surprisingly loud “tip tip tip tip tip sippp sippp sippppp ti ti ti ti ti” song. A flock of dozens of these warblers will soon make a birder search for other species, and the full helping of the Tennessee Warbler is soon forgotten. On these dazzling spring mornings, the Tennessee Warbler is often but a overabundant appetizer, say cheese and crackers, to the buffet of warblers to be had. However, as May wanes, so does this warbler, and soon it is gone, and often unseen, until spring returns.

Tennessee warbler, photo by Jeff Bryant

Tennessee warbler, photo by Jeff Bryant

However, right now marks an excellent time to catch that Tennessee Warbler once more before it makes its way south to its namesake Volunteer State (where it only migrates through) and even further south to South America.

Once in South America, this warbler will often reside in shade-grown coffee plantations, where abundant flowering trees provide plentiful insects and nectar. This habit led ornithologist Alexander Skutch to suggest “coffee warbler” as an alternative to the misnomer of Tenessee Warbler.

Shade-grown coffee plantation, photo by Marshal Hedin

Shade-grown coffee plantation, photo by Marshal Hedin

In reality, these are birds of the high northern latitudes, breeding in openings of the boreal forest. Nests are constructed in hummocks of sphagnum and sedges, and because the spruce tree is a characteristic boreal tree, a favorite menu item of the Tennessee Warbler is the spruce budworm, which can break out and defoliate forests of spruce.

Some forestry operations in Canada will spray entire forests with insecticide in order to inhibit the spruce budworm, and more recent advances have led to lepidoptera-specific insecticides. Researchers in Canada have sought to understand whether this spraying affects the Tennessee Warbler, and have discovered that the females will alter feeding behavior in sprayed areas, and as a result will spend less time tending to their brood. However, no negative effects were found on the brood survival. Whether the long-term effects of this spraying will reduce populations of Tennessee Warblers remains to be seen, but their population is stable for now.

Tennessee warbler, photo by Russ Wigh

Tennessee warbler, photo by Russ Wigh

Again, it’s very rare for the bird to breed in Wisconsin; in the second Breeding Bird Atlas, birders only coded two Tennessee Warblers as “probable” for the entire state of Wisconsin. But these warblers are abundant for the moment, and you might find them in woodlands throughout the state as they make their way south, hopefully to a nice sustainable coffee plantation.

Written by Drew Harry, Faville Grove Sanctuary land steward

Hooded Warbler

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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

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

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

Hooded warbler, photo by Andy Reago & Chrissy McClarren

Common yellowthroat, photo by Kelly Colgan Azar

Common yellowthroat, photo by Kelly Colgan Azar

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Dave Inman