Where did the summer go? The departure of most of our swallows and flycatchers indicates the fall migration has begun. The floodgates will soon be open as warblers, vireos and hummingbirds will leave us, followed by sparrows and hawks. Today’s column is a potpourri of short items based on the theme of migration.

We delight in the spring arrival of migrating birds and claim them for our own. But when you think about it, the many species of birds that migrate from the tropics to nest in temperate North America spend only a minority of their time on our continent.

A ruby-throated hummingbird nesting in Maine is here for only about three months. Migration to and from Costa Rica might require another two months or so. These hummingbirds are really Central American birds that grace us with their presence for a short time each year. The same can be said for bobolinks in Argentina and Bolivia, cliff swallows throughout South America, Baltimore orioles throughout Central America and numerous other migratory species.

Birding for songbirds during fall migration requires more effort than is needed during the spring migration. Fall migrants do not sing and have molted into their less conspicuous basic plumage. The phrase “confusing fall warblers” is so true.

Although most passerines do not migrate as a flock, migrants in a particular patch tend to gather in mixed-species flocks as they forage to fatten up for the next migratory leg. Fall birding in a forest is therefore hit-or-miss with often long periods of misses. A good trick is to find the chickadees. Migrant warblers and vireos often forage with the chickadees.

As an example, I was recently at Quoddy Head State Park in Lubec with a couple of friends. We had walked over a mile with scarcely any birds. At the margin of the bog, I heard a couple of chickadees. I began “pishing” (saying the word pish quickly – if you don’t know the technique of pishing, do a YouTube search for it). As expected, the chickadees approached to investigate the source – but so did about 25 warblers. We were surrounded by black-and-white warblers, black-throated green warblers, yellow-rumped warblers, a common yellowthroat and a red-eyed vireo for good measure.

We know that population numbers of many of these migratory songbirds are declining, notably due to the cutting of tropical forests. A particular problem is the cutting of timber on protected conservation land. These parks and preserves are difficult to police with limited staff and resources.

The monitoring of illegal timbering is done mainly with aerial or satellite images. Environmental managers may not get the photos for several days, and by then the timber thieves have moved on.

Rainforest Connection, a start-up company in California, has developed a way to repurpose old smartphones to detect illegal timber activities quickly. A smartphone is covered in a water-proof case, powered with a solar battery and mounted high on a tree with a sensitive microphone attached. The phone then detects chain saw noises and gunshots. Every five minutes, the phone sends a packet of data to a central server. If the server detects the sound of saws, local enforcement officers are alerted. Similarly, recordings of gunshots can aid in the capture of poachers.

Each phone can monitor an area of about one square mile, and cellphone coverage has penetrated deeply into equatorial forests throughout the world. The service plan costs are modest – only a few dollars a month in most tropical countries. Indeed, the expense is a bargain in exchange for preventing the loss of trees and endangered animals.

I expect we will be seeing more widespread use of this technology.

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