How to find MacGillivray’s, Mourning, Kentucky, and Connecticut Warblers

“I like these. They’re really pretty.”

I glanced away from my computer to see which birds my friend was admiring. She was leafing through a field guide and had settled on the page that showed MacGillivray’s, Mourning, Kentucky, and Connecticut Warblers – the four members of the genus Oporornis. I gave her a wistful sigh and returned to my work.

“How many of them have you seen?” she asked.

“One,” I replied. “They’re really hard to see.”

My friend was not a birder. She had never experienced the agony of staring into impossibly dense brush for a tiny, sneaky bird that refuses to show itself. She said, “But they’re bright yellow. How hard could it be?”

I turned in my chair, affronted, ready to explain the frustration, the heartbreak, and the intense triumph that the warblers inspire, but then I thought again. How hard could it be, really? Is it truly so difficult to find MacGillivray’s, Mourning, Kentucky, and Connecticut Warblers?

To find out, I sought out two of America’s foremost experts on Oporornis warblers: ornithologists Jay Pitocchelli, chair of the biology department at Saint Anselm College in New Hampshire, and Vickie McDonald, research associate at the Migratory Bird Center of the National Zoo in Washington, D.C., and associate professor of biology at the University of Central Arkansas. Each has written about the warblers extensively. This article is based upon their advice.

Search where they breed
“The main reason people have trouble is that they look for the birds during migration,” Pitocchelli says. “Once the warblers begin defending territories on their breeding grounds, they become much more vocal and conspicuous. If you really want to see them, you have to find them when they’re breeding.”

The biggest challenge, of course, is finding the right location. Keep in mind that the warblers occur on breeding territory in areas that are often different from those they pass through in migration. Most prefer regenerating forest, and all will be found in or near low, dense, tangled cover. All Oporornis warblers nest, feed, and remain on the ground or close to it, so keep most of your attention focused at eye level and lower.

To scout for areas, check with local groups, consult breeding bird surveys for sites within your target’s range, and read online reports and mailing lists. “Following recent reports to find territories can be extremely helpful,” notes McDonald. “Habitat that held breeders last year will likely have them this year, and getting specific locations can save hours of unproductive searching.”

Pick the right time of year
Equally important is the time of year you choose. To make the most of fleeting moments of conspicuousness, try to be in a good location while the warblers are singing and establishing territories.

All of the warblers are late migrants: The first MacGillivray’s and Mourning Warblers appear on their breeding grounds from early to mid-May. Connecticut and Kentucky Warblers trickle in from late May through June. This means that your odds of locating active, singing adults are best from early June through early July, so aim for this window when planning a trip.

Once active nesting begins, generally in late June through July, parents can become much less furtive as they try to provide for their young. Food demand reaches its peak later in the season. Adults forage actively throughout the day and often will focus more on catching insects than on avoiding detection – good news for birders. In addition, nesting pairs can be uncharacteristically bold and aggressive as they approach and scold intruders to defend their young.

In this case, as with most inconspicuous birds, knowing what you are listening for can make all the difference. Learn the song of your quarry before heading out into the field.

You could easily devote lots of energy toward finding a bird calling in the right habitat only to find a very common bird producing it, not the Connecticut you thought you were hearing.

Sit, don’t walk
I have read (and written) scores of unsuccessful trip reports that begin with, “We walked all over the place and didn’t see a single warbler!”

The problem? The word walked. Your movements are much more likely to disturb Oporornis warblers than their canopy-dwelling brethren. Each will freeze, hide, and skulk when it detects your presence.

Counter this behavior by adjusting your own. Wear drab, earth-toned clothing. Stand or sit in a likely spot for at least 10 minutes before moving on, and once you do, move as quietly and deliberately as possible.

Not only will moving slowly prevent you from alerting your target to your presence, but it will improve your chances of noticing a nearby bird. A soft call is hard to hear over the sound of debris being crunched underfoot, and a tiny movement is easy to miss if your view is constantly changing.

Look for thick tangles
OK, the simple reality is that it’s more convenient to observe warblers along their migration route than in the nearest breeding area, and most birders’ only chance to see them is when they are passing through. Finding migrants is much more difficult and less predictable than finding breeding birds, but many of the same rules apply and can be used to improve your success.

Seek out thick, dense tangles of understory brush in mature forests. Check reports to find recent locations. Dress in drab colors, and restrict your movements to a crawl. Areas with downed trees in overgrown clearings can be great; they provide both habitat and security for the birds and enough open patches for you to spot them as they move through gaps created by logs.

You may even have luck setting up a camp chair in a likely spot in the morning or afternoon and waiting for the birds to pass through. They’re migrating, after all. They will be feeding busily to prepare for the next leg of their journey.

Find indicator species
Focusing an outing on Oporornis warblers will help concentrate your energy in the most likely areas, but it can work against you if your scope is too narrow. It’s all too easy to picture the ideal habitat and pursue it exclusively even when it may not be habitat the birds prefer. If the birds aren’t singing, it’s nearly impossible to determine their presence without investigating each likely spot thoroughly. Not only is this laborious and exhausting, but it could also be a complete waste of time.

Researchers avoid this pitfall by looking for what are known as indicator species – conspicuous, common species that occupy the same or similar habitats as the bird they are searching for. If enough indicator species are in residence, then the presence of the target bird is implied, allowing the researchers to pinpoint the best areas, including ones that seemed less than ideal.

Pitocchelli uses indicator species extensively when searching for Oporornis warblers. “We focus on finding areas with two or three indicator species to make sure we’re in the right area,” he says. “It’s much more reliable and efficient than waiting for the birds themselves to show their presence.”

The key is choosing indicators that not only are conspicuous enough to be found quickly and reliably but also have fairly specific habitat preferences. A Northern Cardinal, for example, would be a poor indicator. Certainly, it is easy to detect in its range, but it inhabits a wide variety of habitats, so its presence says little about the suitability for a target species. A much better choice would be a Fox Sparrow, which is still common, familiar, and conspicuous but has habitat needs that align more exclusively with those of Oporornis warblers.

Multiple indicators are also crucial. Oporornis warblers inhabit complex, intricate habitats and will be found in areas where a number of separate micro-habitats meet. Sighting a Fox Sparrow alone doesn’t mean that a Mourning Warbler is nearby. The sparrow represents only one of the many conditions needed to support Oporornis, namely tangled brush and thickets.

Now, if you can locate a Fox Sparrow and a Rose-breasted Grosbeak (which favors edges in mature deciduous woods) in the same area, you’re getting warmer. Add a Chestnut-sided Warbler (disturbed or regenerating areas), and you’re almost certainly in a good area. Mourning Warblers prefer dense thickets in regenerating disturbed areas within larger tracts of mature woodland, and the simultaneous presence of all three indicators represents the right combination of micro-habitats to support them. Start with the indicator species listed in the accompanying species profiles. Then customize your choice of indicators for your specific location.

Do not disturb
In your pursuit of these fantastic birds, remember that they are shy for a reason. Since they are ground dwellers, they are especially vulnerable to human disturbance. Bushwhacking into thickets to flush birds degrades the habitat they depend on and may even result in the abandonment or destruction of nests. It also creates inroads for predators, even if no obvious permanent damage is caused. Many Oporornis predators are mammals, and they can easily follow your scent trail to areas with active nesting. Help keep your birds’ locations a secret to their enemies; stick to well-established roads, paths, and trails when searching.

Tape recordings should be used to learn your target’s song, not for drawing it out of the safety of its habitat. Playbacks place unfair stress on your target, and the birds can certainly be found without resorting to this questionable short-cut.

How hard it was
As I found out several months after my meeting with Pitocchelli and McDonald, your best allies in your hunt for Oporornis warblers are persistence and patience.

I stood in a patch of regenerating forest in central Washington State in June, staring into a tangle of salmonberry at the edge of a 10-year-old clear cut. From somewhere inside came a persistent chitt call, maddeningly close. A shadow flicked beneath the plant’s jagged leaves. Chitt. This was it.

All the careful site selection, all the expert advice had gotten me here. All I had to do was find the bright yellow bird in front of me. As I looked, my friend’s question recurred to me:

How hard could it be?

Minutes rolled by as the shadow picked its way through the thick brush. Fifteen came and went, then 30, then 40, and I got not so much as a glimpse. And my legs were getting stiff. Frustrated, I sighed, lowered my binoculars, and started back up the road to find a more obliging species.

But then a sudden burst of loud scolding erupted from the brush, startling me. I turned back and was surprised to see not one, but two target birds – a male and a female MacGillivray’s Warbler.

Brilliant yellow and bright olive, with a sleek, gun-metal-gray hood, the male was dazzling. His broken eye ring flashed silver-white, seeming more like war paint as he rattled his displeasure at me. The female showed more modest garb but a more fiery disposition, chattering non-stop and flitting spastically from perch to perch in front of me.

I took the hint and backed up the road. Both birds advanced a bit to see me off, then retreated into the dense tangle. I released the breath I had been holding and walked back to my car with a grin a mile wide.

That wasn’t hard at all.

10 GREAT SPOTS

1 Rice Lake NWR, Minnesota

2 Tamarac NWR, Minnesota

3 Appalachian Trail, Maryland and Virginia

4 Shenandoah National Park, Virginia

5 Holla Bend NWR, Arkansas

6 Burning Well, McKean County, Pennsylvania

7 Adirondack Park, New York

8 Sevenmile Guard Station, Klamath Basin Birding Trail, Oregon

9 Mount Hood Loop, Oregon Cascades Birding Trail, Oregon

10 Gifford Pinchot National Forest, Washington

5 TOP TIPS

1 Look for low, dense, tangled cover in regenerating forest.

2 Focus your attention at eye level and lower.

3 Search when warblers are singing and establishing territories.

4 Stand or sit. Don’t walk.

5 Look for indicator species.

KENTUCKY WARBLER
Where to watch: Dense, vine-tangled habitat in woodland in the latter stages of regeneration. To attract Kentuckys, ­undamaged understory vegetation must be intact and diverse, ideally composed of wild grape vines, spicebush, may apple, and bloodroot.

Your strategy: Focus on areas where the thick habitat is broken by trails, streams, or downed trees. Areas that have been ­naturally regenerating for about 18 years ­after complete destruction of mature woods are just about perfect. Follow trails slowly in early morning during late spring, listening for singing birds.

Indicator species: Acadian Flycatcher, Wood Thrush, American Redstart. If you encounter an Ovenbird, you’re very close. Try to find slightly moister areas in similar habitat.

CONNECTICUT WARBLER
Where to watch: Connecticut Warblers breed in boreal tamarack and spruce bogs, specifically the brushy margins where woods lead into marsh, and they will seek similar habitat while migrating. Look in soggy thickets, wet forest edges, and overgrown boggy ditches in migration.

Your strategy: Mid-May into June is best during migration. Focus your efforts in late afternoons. Bring a camp chair, and stay put for an evening, watching for movement on or near the ground. (Connecticut Warblers bob as they walk, reminiscent of Spotted Sandpiper.) Within their breeding range, listen for singing birds early and late in the day in borders of tamarack bogs.

Indicator species: On breeding grounds, Alder Flycatcher, Lincoln’s Sparrow, and especially Palm Warbler.

MOURNING WARBLER
Where to watch: Dense thickets in ­regenerating disturbed areas within larger tracts of mature woodland, ­preferably near riparian areas. Second growth from clearcuts, natural disturbance, and oil ­exploration are good starting points, as long as moderately closed woods are nearby. Generally 3-15 years following a disturbance is ideal.

Your strategy: Drive or walk up old ­logging roads and trails, pausing quietly for at least 10 minutes in likely spots. Mornings in June and early July are best to find singing adults. Focus also on mid-July, when adults will be active foraging to feed young.

Indicator species: Rose-breasted ­Grosbeak, Fox Sparrow, Chestnut-sided Warbler.

MACGILLIVRAY’S WARBLER
Where to watch: The western counterpart of Mourning Warbler, MacGillivray’s favors very similar habitats: ­regenerating ­disturbed areas. Dense understory is ­crucial, and riparian areas are more strongly favored.

Your strategy: Nearly the same as ­Mourning Warbler but to much higher elevations (up to nearly 10,000 feet). Focus on open patches in dense thickets at ground level or just above. MacGillivray’s will seldom venture much higher.

Indicator species: Black-headed ­Grosbeak, Fox Sparrow, Lazuli Bunting, Wilson’s Warbler.

Chris Duke is a nature writer based in Seattle who has worked as a wildlife biologist for the World Parrot Trust in Bolivia. He wrote about finding rails in our February 2009 issue. He thanks ornithologists Jay Pitocchelli and Vickie McDonald.

Originally Published April 24, 2009