For many birders, the next two weeks will offer the most exciting birding of the year as spring migration proceeds. The migration has been going on since late February when the first turkey vultures, red-winged blackbirds and common grackles arrived in the state after a winter’s sojourn to the south.

The pace of migration has been building in the past couple of weeks with the arrival of northern flickers, hermit thrushes, yellow-rumped warblers, palm warblers, and white-throated sparrows. The floodgates are opening now. A good morning of birding may produce a score of warbler species, several species of vireos, scarlet tanagers and many flycatchers among others.

The birds are arriving with urgency. Hormones are increasing and reproduction is on every bird’s mind. Males are dressed in their best finery and singing loudly and frequently, making it easy for a birder to document their presence. Our trees will not leaf out fully for a couple of weeks, so viewing opportunities of birds are excellent.

Not all the migrating birds we see in Maine will stay to breed. Some are just passing through, passage migrants in ornithology-speak. Some like white-crowned sparrow and many of the shorebirds are all bound for more northerly breeding grounds. But many  migrants belong to species whose breeding range includes Maine and more northern regions. There is no way to know if the magnolia warbler you see this week will stick around in Maine to nest or head for Quebec.

Have you ever wondered when is the best time to look for a particular species during spring migration? Perhaps, you want to find your first Philadelphia vireo. When should you be out in the field?

That information is available thanks to the participation of over 400 Maine citizen-scientists. Between 1994 and 2017, I coordinated a spring arrival-date project in which volunteers were asked to send in their first sighting of 105 common migratory breeding birds along with their location. I created a web tool that allows you to see the reported arrival dates of a species of interest. Check it out at: hobbes.colby.edu/arrival/

The data collected provided a way to look at the timing of migration through the state. The analysis is constrained because most of the records come from coastal areas or the I-95 corridor from Portland to Bangor. I had too few records to include the northern half of Maine or the western mountains.

Nevertheless, 42 of 98 species did show some variation in arrival over these areas. Sixteen species arrived latest in Washington County (e.g., turkey vulture, american kestrel, eastern kingbird, northern waterthrush, american redstart). Seven species arrived earliest in the Hancock/Waldo/Knox county region (e.g., gray catbird and Canada warbler). Three species arrived latest in the Augusta to Bangor area compared to coastal areas (e.g., ruby-throated hummingbird). The other variable species had more complex patterns but the general trend was for latest arrival in Washington County.

INSECT DECLINES

In the last column, I discussed two recent scientific articles that presented depressing and convincing evidence of broad declines in the birds of North America. This week, I want to discuss a couple of recent articles on insect declines.

The fate of birds and insects are tightly linked. Some birds like flycatchers, swifts and swallows capture insects on the wing. Others like cuckoos, warblers and vireos glean larval insects from leaves. Nectar-feeders like hummingbirds and seed-eaters like sparrows capture insects as a great source of protein for their nestlings. Many insects are critical components of food webs on which hawks and owls depend.

A review by David Wagner showed that flying, ground and aquatic insects are declining worldwide and some extinctions have been documented. A paper by Van Klink and colleagues compiled data from 166 long-term surveys. They found that terrestrial insects are declining by 9% per decade. That is frightening!

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

whwilson@colby.edu

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