A crested caracara is shown during an exhibition in Cota, Colombia, in 2018. Three appeared in Maine from May 23-25 in Fryeburg, Cape Elizabeth and Round Pond. Fernando Vergara/Associated Press

The glorious spring migration is nearly over. The arrival of the last black-billed cuckoos and Nelson’s sparrows signal the end of the spectacle. Now we can tune our ears to the various songs our nesting birds are making.

The spring arrival of our migratory breeding birds, in their colorful breeding plumage, stands alone as an awesome phenomenon. But this period of movement is made even more exciting by the appearance of vagrant species, species that generally do not nest in Maine. This spring has been one of the most exciting ones in my memory for vagrants.

How do these birds end up out of place in Maine? The answer is complicated, and we have much to learn about the reasons vagrants show up in unexpected places.

Some vagrants arrive because of overshooting. Such birds breed to our south. Either because of navigational error or strong winds, these birds appear briefly in our state, realize their error, and presumably head back south to seek a mate.

Three good examples are a yellow-throated warbler in Sanford on May 2, a worm-eating warbler on Monhegan Island on May 17, and a hooded warbler at Fort Foster in Kittery on May 10. The northern limit of nesting is Massachusetts for the first two species and Pennsylvania for the hooded warbler.

A summer tanager is seen during a birding tour near Kingsville, Texas, in 2009. The species breeds as far north as Pennsylvania; one was seen on May 3 in Pembroke in eastern Washington County. Eric Gay/Associated Press

Other examples include yellow-crowned night herons that appeared at Dyer Point in Cape Elizabeth and Stratton Island, east of Old Orchard Beach. They breed regularly as far north as Connecticut. Summer tanagers breed as far north as Pennsylvania; one was seen on May 3 in Pembroke in eastern Washington County.

Several white-eyed vireos appeared in Maine; they do not nest north of Connecticut.

Multiple black vultures appeared in Maine. Their current northern nesting limit is Massachusetts.

We had at least two records of chuck-will’s-widow this spring in Hancock County. Their nesting limit is Long Island in New York.

We need to keep an eye on these vagrants that breed relatively close to Maine. Vagrants may decide that Maine would be a fine place to breed, particularly with global warming effects. The gradual movement of vagrants into Maine in the past 40 years has led to the establishment of turkey vultures, red-bellied woodpeckers, tufted titmice, Carolina wrens and house finches as regular breeders. Who will be next?

We had other vagrants from the eastern United States that nest well to our south. These birds overshot spectacularly. A Mississippi kite at Cape Neddick in York on May 13 was more than a thousand miles north of its breeding range.

A white pelican was spotted in Portland on May 15. This species mostly breeds on freshwater lakes in western North America, although some non-breeders occur along the Gulf coast.

Perhaps the most exciting vagrant this spring was the crested caracara, a ground-foraging falcon. They nest in central Florida and Texas. We had one prior record of the species in Maine in August and September of 2014. Three appeared in Maine this spring from May 23-25 in Fryeburg, Cape Elizabeth and Round Pond.

Maine had several vagrants from the western part of North America this spring. I expect that navigational errors explain these remarkable records, including a rufous hummingbird in Frankfort on May 1, a Harris’s sparrow in late April in Turner, and white-winged doves in Farmington and Pemaquid on May 24.

Coastal birds often show high levels of vagrancy. This spring saw several records of Caspian terns along the coast, as far north as Washington County. There also was a brown pelican in Kittery, a black-necked stilt in Scarborough, and several white-eyed ibises in southern coastal Maine.

Finally, there are head-scratchers. What was an arctic-breeding king eider doing in Maine at Fortunes Rocks in Biddeford in late May? How about a Eurasian golden plover in Scarborough on May 21? A Pacific loon at Ferry Beach in York County on May 2?

We may not understand why these vagrants arrived in Maine, but it is surely a thrill to see them.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu