We couldn’t resist going birding again this week at a new favorite spot, the Harrison Avenue Nature Trail in Gardiner, which we mentioned in last week’s column. Our “greed” for warblers was unrelenting but we were now in the month of June, when conventional birding wisdom often considers migration to be over and the nesting season begun. We know otherwise—many birds are still migrating into early June—and in this odd year of warm-cold-warm-cold weather, the likelihood of finding migrant warblers still flitting around seemed even greater.

We were not disappointed. Blackpoll warblers by the dozens filled the trees along the entire trail and, while numbers of other species were fewer, the list remained long: American redstart, magnolia warbler, Canada warbler, blackburnian warbler, mourning warbler, Wilson’s warbler plus loads of migrant red-eyed vireos and a smattering of flycatchers—least and alders, and eastern kingbirds.

Many of these birds were feeding in the newly leafed out ash trees along the trail, which borders and overlooks Cobbosseecontee Stream. It highlighted for us the almost miraculous way in which the cycles and seasonality of nature intertwines to make life, including our own, possible on Earth.

Even the fact that trees and other plants can take sunlight and something we can’t see out of the air called carbon dioxide and turn it in to leaves and flowers and roots and wood is mind blowing. Add to that the fact that the byproduct of that process sends out oxygen that we humans and just about everything else literally can’t live without.

Migrant birds arrive in successive ways in places like Maine in the northern hemisphere just as more sunlight is spilling onto the land and plants are able to start taking advantage of it to grow and flower. Fortunately, those plants don’t burst into green leaf and showy flower all at the same time. Newly growing plants and recently thawed rivers, streams, and lakes host newly hatching insects. But again, different insects hatch at different times through the season.

All of this means that the March arrival of tree swallows and palm warblers, the April arrival of black-and-white warblers and barn swallows, the May arrival of blackburnian warblers and Baltimore orioles, and the June migrating blackpoll warblers and olive-sided flycatchers ALL will find food along their migratory path.

While we birded along the Harrison Avenue Nature Trail we were accompanied by the persistent high shrieks of several osprey and the sounds of a few dozen herring gulls. Those birds signaled that another interwoven cycle was at work. Alewife, a silvery species of river herring, were amassing by the thousands in Cobbosseecontee Stream as they returned from the Gulf of Maine to attempt to breed upstream. We say “attempt” because today there are three dams in the span of the Nature Trail’s length that block their passage to the breeding grounds. The osprey, gulls, herons, eagles, and other birds still feast on the ones that come into the stream and a few make it upstream with human help (including through a program carried out by students at Gardiner High School that our son has participated in). A small nonprofit appropriately named Upstream is working for passage of alewife and other migratory fish species from the ocean through Cobbosseecontee Stream.

The birds catching alewives were not migrating but were getting those fish to feed their young. So while some birds were still migrating and were perhaps a thousand miles or more from their nesting grounds, other species were already feeding young. And while the willow and poplar trees had flowered and leafed out in April, the ash trees were just starting to show their young, fresh leaves.

The intermingling cycles of life are truly amazing.

Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists and author of “Birder’s Conservation Handbook”. His grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells, formerly of the Cornell Lab of Ornithology, is a senior director at the Natural Resources Council of Maine, a nonprofit membership organization working statewide to protect the nature of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds” and “Birds of Aruba, Bonaire, and Curaçao: A Site and Field Guide” from Cornell Press.