I always look forward to autumn with its crisp, cool days, brilliant foliage, and absence of bugs. But these changes bring about something I don’t especially look forward to, although I am always fascinated by it – bird migration.

Now the late summer silence broods over meadow and forest. American goldfinches admirably fill the vacuum left by songbirds that are now busy fattening up for their marathon trips south. In fact, it seems as if I’ve never heard their sweet, whimsical songs before – during the neotropical songbird rush and excitement, they were easily overlooked.

However, long after neotropical songbirds have finished nesting, goldfinches are practically just starting their breeding cycles.

Goldfinches breed late in the season, timing their nesting efforts to coincide with the flowering of thistles, an important food source, according to their “Birds of North America” species account. In addition, researchers think their whole-body molt in spring (during which they turn from drab olive to bright yellow) places too much stress on their systems, making early nesting impossible.

The “Sibley Guide to Bird Life and Behavior,” provided me with an additional explanation for this deviation: unlike other songbirds that become heavily “insectivorian” during the spring and summer, goldfinches (and other members of their family) remain almost completely vegetarian during the summer months, scarfing up seeds and buds of grasses, shrubs, and flowers.

Seasonal signs are all around us. Our neotropical songbirds are undergoing plumage changes now. As if it weren’t enough of a challenge to identify them without their signature songs! Not only are they silent, these “confusing fall warblers,” sometimes look nothing like what they did during the breeding season (and forget about the young birds in their juvenile plumage, who sometimes don’t resemble their parents in the least bit). I consider myself lucky to simply see them – and when I do, they are always quietly flitting about the tree canopy catching insects.

A little more visible and comparably – notice I said comparably – easier to identify are the shorebirds. They have been gathering around the low-water level of ponds and lakes, and on the beach flats of low tide. Look for them as they probe their long bills into the soft ooze of mud and sand for delectable and fattening tidbits.

Large flocks of migrating common nighthawks have been spotted throughout the past few weeks, and starlings, red-winged blackbirds, and grackles are congregating in noisy groups. Swallows – those that returned and bred successfully – are now largely absent; only an occasional barn swallow or chimney swift have I seen wing its lonely way across the changing skies.

Soon the main push of neotropical migrants will be under way, followed by their main predators – the raptors. Then you truly will be witness to the grand spectacle of migration.

Chris Corio, a volunteer at Fields Pond Audubon Center in Holden, can be reached at fieldspond@juno.com