The pace of the fall migration is diminishing but late October and early November can produce some remarkable bird sightings. One such sighting is a report of a Tropical Kingbird in East Machias by Wendy Sawyer on October 29. Two more were seen at the same time, one in Cambridge Narrows, New Brunswick and one in Massachusetts. If confirmed by the Maine Bird Records Committee, the Machias bird will be the second Maine record. The first was a specimen collected on Halloween in 1915 in Scarborough.
Tropical Kingbird is a resident from central Mexico south to most of South America. There is a migratory population that moves into southeastern Arizona to nest every year. We do not know the provenance of the recent records. All we do know is that they are a long way from home!
These sightings add to a remarkable list of vagrant flycatchers in Maine in the late fall. We have four accepted records of late-fall Ash-throated Flycatcher (two from Monhegan Island, one from Seal Island in Knox County, and one from Saco). A Gray Kingbird appeared in Ogunquit between October 31 and November 6, 2010. We have several reports of Say’s Phoebe in the late fall from Monhegan Island and Bar Harbor. Most astounding of all is a record of Variegated Flycatcher (a South American species) in Biddeford between November 5 and 11, 1977.
I think the most reasonable explanation for the appearance of these southern and western flycatchers in Maine in the late fall is navigational error. All of these species capture flying insects for most of their dietary needs. Flying insects are in pretty short supply in Maine now so the flycatchers must switch to other sources of food.
Swallows are aerial insectivores as well. We have five records of Cave Swallows in Maine in November (Kittery, Ogunquit, Cape Elizabeth and Scarborough). These birds must have been challenged to find food while they were here.
We have records of two vagrant hummingbirds in Maine in the late fall. A Calliope Hummingbird was in Blue Hill October 23 to November 1, 2008. A Rufous Hummingbird was present in Phillips until Halloween, 2006 and another was present in mid-November, 2001. All of these birds must have been assisted by provision of hummingbird feeders.
It would be great to know what ultimately happens to these extra-limital birds that end up in climates that tax their ability to find preferred food. Perhaps some are able to correct their errors and move back south or west. I suspect that most of these birds succumb to starvation.
In the last column, I wrote about the increase of multi-disciplinary approaches in ornithological research. Such a study, related to migration, just appeared in the most recent edition of The Auk, the leading ornithological journal in North America. In this case, techniques in cell biology and biochemistry help us understand the costs of migration.
The DNA in our cells is organized into chromosomes, long chains of genes. In humans, we have 23 pairs of chromosomes, housing 40,000 genes. At the tip of each chromosome, a structure called a telomere acts as a cap, protecting the DNA on the chromosomes.
Our telomeres shorten as we age, increasing our chances of dying. Telomeres can also shorten in response to cellular stress.Carolyn Bauer and colleagues studied first-year Dark-eyed Juncos wintering in Virginia. Some of those juncos were born in that area and do not migrate. Others were born to the north, perhaps in Maine, and migrated to Virginia to spend the winter.
All the birds analyzed were of the same age, differing only in whether they had a migration under their wings. As predicted, the migratory juncos had shorter telomeres than the resident birds. The results indicate one of the costs of a migratory life style is an increase in the rate of shortening of the protective telomeres.