To park visitors taking a summer walk in the park, June, July and August probably seem pretty interchangeable. Birds have nested, trees are green, flowers are in bloom, and butterflies are flitting about.

To park visitors taking a summer walk in the park, June, July and August probably seem pretty interchangeable. Birds have nested, trees are green, flowers are in bloom, and butterflies are flitting about.

But the circles of life for plants and wildlife are ever-advancing as the summer progresses, and behavior changes in ways big and little. Birds can be used as an example, and since Preservation Parks soon will hold its Summer Bird Walk series, they're logical ones to explore.

There was no way we could ignore the birds' mating calls in the spring; we were awakened in the morning by a true cacophony -- many birds vying for airtime in which to broadcast their messages: "I'm the best; I'm the strongest; I'm the best choice as a mate."

Then it was the twitter of baby birds begging for food. In their own little ways, they seemed just as noisy at 5 a.m. as their dads.

Things have quieted since as eggs have hatched and babies have left their nests to go off on their own. That's not to say that the nesting-hatching-fledging process is over for the year -- some birds, such as the northern cardinal, produce multiple clutches each season -- but the general hubbub has diminished some.

At Preservation Parks' June bird walk, we focused on the waning nesting season, looking for babies that were just getting ready to fledge. Lending some excitement this summer, a Cooper's hawk chose to nest along the trail at Deer Haven Park, and visitors have been delighted to see this bird flying just overhead. The babies have since fledged, but still can be seen near the junction of the Tree Swallow and Bent Tree Ridge trails.

Nature has turned up other delightful surprises as the summer has progressed. During the June walk, participants spotted an orchard oriole.

Rust-colored with a black head and throat, this bird lacks some of the flash of its bright orange cousin, the Baltimore oriole. But it was a find nonetheless, and fun to see in a park such as Emily Traphagen, which is surrounded by development. This will be one of the birds that will migrate south this winter, so we enjoy it while it is here.

There are two more Summer Bird Walks on the schedule this month and next. We'll meet at 8 a.m. July 30 at Gallant Woods Park to look for the young ones out testing their wings and searching for food on their own. In July, they can find plenty to eat. Flower seed heads and berries are -- and will be -- in abundance, as are a multitude of insects. At Gallant Woods, and at Gallant Farm across the street, nest gourds for purple martins and nest boxes for tree swallows and eastern bluebirds provide homes for mosquito-eating birds -- a great benefit to humans this time of year.

Unlike mammals, birds don't eat extra in summer to get through the winter. Among other reasons, they have to stay lightweight to fly off for migration. Instead, birds follow the food source. As long as there is plenty to eat here, they can stick around. But instinct and long history tell them that food will disappear as the days get shorter, and they begin preparing for migration, even as the food stores stay healthy up north.

Migration will be the theme of our last Summer Bird Walk, set for 8 a.m. Aug. 27. We'll meet at Blues Creek Park to look for birds as they begin to prepare for colder temperatures, and maybe a long trip south.

All of the bird walks are free, for ages 7 and older, and do not require advance registration. You can bring your own binoculars, and we will have a few sets to loan for the walk. Please join us to learn more about how birds change behavior, feathers and locales as the year goes on. The series continues into the fall, and information will be available in the Preservation Parks Autumn Program Guide, available by mid-August.

For more information about parks and programs, visit preservationparks.com.

Sue Hagan is marketing and communications manager for Preservation Parks of Delaware County.