Southbound Warbler Migration in Michigan’s Eastern Upper Peninsula


Northern Parula and Black-throated Green Warblers in a flock of warblers

On some late summer days warblers congregate at Michigan’s Eastern Upper Peninsula (EUP) peninsulas, driven by north winds. Especially when they happen to head toward inclement weather over Lake Huron while migrating south at night.

August 21, 2022 was one of those days, and it reminded me that this article has been long overdue. During the early morning dark hours after midnight, a fog developed over Lake Huron. The migrating flocks, which contain many species of warblers, flew without much risk over land, but ran out of land when they approached peninsula tips. They saw nothing but fog to the south, and they could not see land on the other side of the lake. So, they dropped to the peninsula forests, with the majority of birds committed to waiting for another north wind night without fog over the lake in order to move onward. Rain (and especially thunderstorms) over the lake can produce the same result.

Blackpoll Warbler in mid-September

The period between mid-August and mid-September is the best time to witness the southbound migration of warblers in this area. That is the traditional time when the majority pass through and any night with north winds could drop migrant warblers on a peninsula, such as the one where I live. But, on many north wind nights during this period the warblers do not migrate because they are not in a hurry to get to nesting territory and claim and defend it, as in spring. They are going south for the winter because they are too small to survive the cold temperatures, and the majority of them need live insects to sustain them. Spring migration during the ideal warbler migration time for this area (May 19-31) is different. Any night with south winds will bring many warblers to the area. This is one of the reasons why I run a photography workshop for warblers in the spring, but not during late summer. In late summer the presence of warblers is too unpredictable.

Magnolia Warbler in late August

On the morning of August 21 I awoke to thousands of warblers of at least 17 species, everywhere on our peninsula. A fallout of this magnitude hadn’t happened in late summer for many years, and this time I was prepared with the perch locations in place from the spring warbler workshops. And I had very light winds and cloudy conditions – the perfect conditions for warbler photography. I could point the camera in any direction without concern for harsh shadows and I could photograph most of the day, without concern for harsh light. If the winds were strong the rustling of the trees would have spooked the warblers, making photography impossible.

Another factor was migrating hawks. I did not need to worry about them. In mid-to-late August they are too busy with the final stage of getting their young independent and are not migrating through the region. That changes in early September, when two species, Merlin and Sharp-shinned Hawk, move into the peninsula and hunt the migrating flocks for a few days before moving on. When either or both of these two hawks are around it can be almost impossible to get good images of the warblers because they stay on alert and hidden within the trees. For an article touching upon this see: The Hunters and the Hunted | paulrossibirds.

Northern Parula in mid-September

I have photographed the warbler flocks of late summer since 2007, an incredible year when there were 4 days in a row similar to August 21, 2022. The flocks showed me how they like the safety of the cedars of our peninsula and prompted the creation of my prepared perch locations within select cedars. Those trees are at forest edges in good light, and I simply trim a few tips of branches periodically, near eye level up to about 9 feet, so the natural perches have an unobstructed view from photographers, and I add a perch or two.

Female Golden-winged Warbler just before mid-August; the only individual of this species which I have found during southbound migration. It migrated early, and stayed for a few days. It joined the local family groups of American Redstarts, Black-throated Green Warblers, Black and White Warblers, Northern Parulas, Yellow Warblers, and sometimes Blackburnian Warblers, which all flock together before heading south.

It took me years to learn the typical plumages of the 22 species of warblers that regularly show up in the flocks roaming our peninsula during the southbound migration season. And this was sometimes just to identify what species I photographed, and which species I would eventually target because they rarely were present in the flocks. There are adult males and females, and hatch year males and females (born in early summer), and all 4 have a different look for all of the 22 species. There are also differences based on the progression of molting of individual birds. It gets very complicated. I have simplified things here by omitting molting birds in this article – all of the birds pictured have finished molting or are very close to finishing. For in-depth information on all of this see this reference.

Sometimes determining the age or sex of a bird (including a warbler) is not possible, even if experts have the bird in hand. With some species, such as the Black-throated Blue Warbler below, the difference between males and females is obvious.

Male Black-throated Blue Warbler in mid-September; this species can show up from August to October, but very few are present in the local flocks; note that the male looks nearly identical to its striking plumage in late May, even though it has replaced its feathers. A little gray under its beak is the only difference.

Female adult Black-throated Blue Warbler from August 21, 2022; females of this species have a very different look than males but look very similar to their breeding plumage. The female above can be identified as an adult because it has a white patch on its wing.

Hatch year female Black-throated Blue Warbler; the lack of a white spot on its wing identifies it as a hatch year bird. Note that this bird has more of a blue plumage compared to the bird above – this reflects natural variation amongst all females of this species.

Adult male Cape May Warbler from August 21, 2022; this species passes through our area in late August and early September and is very rarely present after that.

Most individuals of the 22 species have a look somewhat similar to their breeding plumage, as seen with the Cape May Warbler above. With this particular species the adult male has a distinctly different look than females or hatch year birds. For many warbler species, females and hatch years birds, whether male or female, often look very similar.

Blackburnian Warbler in late August – with a look similar to its breeding plumage; this is another species that passes through our area in late August and early September and is very rarely present after that.

Canada Warbler in mid-August; very few individuals of this species join the flocks, and they pass through in mid-to-late August (and rarely the beginning of September), but most are easily identified because they look so similar to breeding plumage birds.

Ovenbird in late August; a very similar look to its breeding plumage; very few individuals of this species join the flocks, but one can show up in August, September, or October.

Wilson’s Warbler in late August; a very similar look to its breeding plumage; a few individuals of this species join the flocks. It is often easier to photograph this species in August or September very close to my home, as compared to the rarely found breeding individuals inland in May or June.

Northern Waterthrush in Mid-August; this species rarely shows up in the flocks but often will approach with a distinct metallic-sounding chip call before it appears. Its look is identical to breeding plumage. During southbound migration I have only found this species in August.

Adult male Black-throated Green Warbler in early September; Adults of this species are distinctive and adult males look similar to breeding plumage and have remnants of their black throat patch. This species is very common in the flocks.

Black and White Warbler in late August; very similar to breeding plumage and very common until late September. This bird was either cleaning its bill after feeding or rubbing off remaining molting feathers close to its beak.

Yellow Warbler in Tamarack in mid-August; there is a wide variety of looks to individuals of this species during their passage in August and September. Only a few of them join the flocks.

Tennessee Warbler from August 21, 2022; this species generally looks quite similar to its breeding plumage and very few individuals join the flocks; it passes through our area in mid-to-late August and early September.

Nashville Warbler in mid-September, most adults of this species look very similar to breeding plumage; this species is sometimes in the flocks; it passes through our area in late August and early September.

Blackpoll warbler in mid-September. This species looks much different than its breeding plumage and passes through our area during September (rarely into October), but on some days a few of them can be found. At this time, depending on sex, age, and stage of plumage, an individual often has a very similar look to a Bay-breasted Warbler, but its yellow feet distinguish it from a Bay-breasted, which has black feet. The streaking on its breast helps distinguish it but that streaking is not always present.

Chestnut-sided Warbler in mid-September; this species passes through in late August to late September and looks very different than its breeding plumage, but all individuals look similar, once molted. They are not present in every flock but occur regularly.

Magnolia Warbler in mid-September; this species looks quite different than its breeding plumage and is more common in the flocks at this time than it is on breeding territory in May and June. It passes through from late August to the end of September.

Mourning Warbler in late August; I have detected only 3 or 4 of these by hearing their distinctive chip calls, but only this individual provided images. It has a very similar look to a Connecticut warbler at this time.

Male American Redstart in late August; males look very similar to their breeding plumage; most common warbler of this area. This species is second to only the Yellow-rumped Warbler in number of days spent in our area. Individuals start arriving in mid-May and the last ones leave in mid-October.

Female American Redstart in mid-September: females look very similar to their breeding plumage; a much different look than the male.

Northern Parula in mid-September; this locally abundant species looks somewhat similar to breeding plumage and very often family groups still stay close together at this time. Some individuals can hang around until October if it remains warm.

Male Common Yellowthroat in early September; the distinctive remnants of its black cheek (from breeding plumage) identify this individual as a male. My perch location near our marsh is where I can photograph this species at this time. This species often hangs around until mid-October.

Palm Warbler in early September; very few join the flocks around here; most are found in the more open habitats inland while migrating south. This species also often hangs around until mid-October.

Yellow-rumped Warbler in early October; this common species stays around typically until mid-to-late October but not many individuals participate as members of flocks.

Orange-crowned Warbler in late September; this species only migrates through our area during the last week of September and first week of October; the large warbler flocks have passed us by then; very few individuals of this species can usually be detected within the kinglet flocks (composed of Golden-crowned and Ruby-crowned kinglets).

Our local warbler flocks are sometimes joined by one or more of three vireo species: Red-eyed, Blue-headed, and Philadelphia. Warbling Vireo nests in small numbers in the EUP, and while I have found one individual in a spring warbler flock, I have not found one in a southbound flock yet.

Red-eyed Vireo in late August; its red eye becomes a brownish color at this time, but its plumage is very similar to breeding plumage; it is common but very few remain into September.

Blue-headed vireo in developing cedar cones in early September; an almost identical look to breeding plumage; few of these birds show up in the warbler flocks, and almost always only in September.

Philadelphia Vireo in late September; an almost identical look to breeding plumage; very few of these birds show up in the warbler flocks, but one can show up between late August and the beginning of October.

In the majority of images above a bird has landed on a branch that is oriented close to horizontal. The branch is thick enough that it is stable for the bird to land on and balance itself, and the bird can grab onto it with its claws, which also helps it stabilize. On such a perch the bird can push off and jump into flight quicker than it could on a flimsy branch. Small birds have shown me that they prefer these types of branches, probably because it’s safer for them to escape a hawk attack, if necessary – its instinct. But they can land in unexpected places, which often yield nice images. The only problem – those places are often flimsy and unstable, and the birds stay there very briefly. So, the ability to center the lens on the bird very quickly is necessary. For a video on this click here.

Below are some examples of images where locally photographed southbound warblers landed very briefly on an unexpected/unseen perch – a few images where the same can be said are also further above.

Blackburnian Warbler in Poplar in early September

Black and White Warbler on a fallen birch in August

Blackpoll Warbler in Tamarack in early September

Chestnut-sided Warbler in late August

Magnolia Warbler in late August

Blackburnian Warbler in late August

Tennessee Warbler in early September

In this article I cover 24 species of warblers (if you count) but mention that 22 are regularly occurring at my location during southbound migration. Golden-winged and Mourning are so rare I do not count them. 27 species could potentially show up. This leaves Kirtland, Pine, and Connecticut as the 3 species I have not photographed near the north shore of Lake Huron at that time.

I have never found southbound Kirtland warblers locally, but the northern most nesting individuals of this species (which are not many) are not far northwest of here. This species has regularly been documented as migrating south through southern Ontario but not southern Michigan. The straight line from their nesting grounds to our northwest and southern Ontario passes very close to here. So, they may pass right overhead but I believe they are not likely to stop here. Assuming they do pass overhead, and do not wander too far from their nesting grounds while raising their young to independence, I think we are located too close for them to stop during the 1st night of their journey. But theoretically some could stop near here if bad weather over Lake Huron stops them. They may subvert this area entirely by crossing the St. Mary’s River well north of here. This way they would avoid crossing Lake Huron and could continue their southbound journey to the east of Lake Huron. I believe that is likely.

Pine Warblers stay as family groups within their white pine habitat not far inland and seem to never join the flocks passing through our area. I have found 2 Connecticut warblers with different southbound warbler flocks but did not have a chance to photograph either well.

Pine Warbler in mid-September in an apple orchard located a few miles inland from Lake Huron; this individual was part of a family group that may have nested in one of the large white pines very close to this tree. The similarities between this individual and the Tennessee above gives a hint at the difficulty of identifying many of the “confusing fall warblers” in-the-field.

When I began to live in Michigan’s EUP full time in 2007 I learned quickly to never go out of my way to photograph southbound warblers. It’s too much of a crap shoot. Only if I have had the time and the birds were actually here after a north wind night, and there were good weather conditions, did I take the time to try. On the good days I would take one look out my windows after sunrise, where I sit writing this, to know if it was a good day – warblers were very visible feeding in the nearby cedars. Over the years, I eventually targeted warblers within the local flocks which had plumages I never saw before, if they were cooperative. Those images are not in this article but are part of a large gallery illustrating a wide variety of plumages: GALLERY OF SOUTHBOUND WARBLERS AND VIREOS OF MICHIGAN’S EASTERN UPPER PENINSULA

Did you notice how many images above had cedar trees? For a photo-documented article explaining the importace of cedars to the tremendous numbers of warblers of our area see: Cedarville – Warbler Capital of North America? | paulrossibirds