Skyways to Pathways: Preserving Wildlife Habitat Along the Treeline

written by Nia Spongberg and Greg L. Hughes

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Chimney swifts (Chaetura pelagica) are medium-sized, sooty grey birds known for their tube-shaped body, long-curving wings, and stiff, shallow wingbeats. They spend the majority of their lives airborne, flying almost constantly except when roosting overnight and nesting. These remarkable birds forage across diverse landscapes, consuming one-third of their body weight daily in insects, accompanied by distinctive high-pitched chittering calls. When swifts land, they are unable to perch on horizontal surfaces, so instead they use their claws to cling to rough, vertical surfaces. The world around them has changed a lot, but Chimney swifts have demonstrated remarkable adaptability — a quality that resonates deeply with our community's own resilience.

As GivingTuesday approaches, consider helping us preserve the critical chimney habitat at 415 West Washington that supports 1,400 Chimney swifts. Read ahead to learn why protecting this unique urban wildlife sanctuary deserves your support.

Threats to Survival

Prior to the arrival of Europeans in North America, Chimney swifts primarily nested in big, hollow trees in old growth forests, as well as in caves and on cliff faces. In the early 1900’s as white settlers widely logged and deforested the land, swifts adapted away from trees and turned to chimneys (now essential for their survival and lifecycle) for their nesting needs. Today, as humans increasingly tear down, cap, or line old clay chimneys with metal, the swifts find less and less available habitat for rearing their young. Climate change and pesticide use are simultaneously disrupting their migration routes and ability to find food. Although the global population of Chimney swifts is estimated at 7.7 million, it has been in a sharp, long-term, range-wide decline of roughly 2.5% per year – or 70% cumulatively – over the past 50 years according to the North American Breeding Bird Survey. In 2010, the International. Union for the Conservation of Nature changed the bird's status from least concern to near threatened. In 2018 the IUCN intensified the Chimney swift's status from near threatened to vulnerable.

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Migration & Reproduction

Chimney swifts are a migratory bird. They spend the winter in the upper Amazon basin of Peru, Ecuador, Chile, and Brazil. In April they arrive in their North American breeding grounds, including Ann Arbor. Once they arrive, monogamous breeding pairs seek to find chimneys in which to rear their young. Only one nesting pair uses a given chimney. They use glue-like saliva from a gland under their tongues to cement their nests to the chimney walls. Nests are a half-saucer of loosely woven twigs, roughly 2–3 inches from front to back, 4 inches wide, and 1 inch deep. Swifts lay 3-5 pure white eggs which incubate 16-21 days. Hatchlings remain in the nest 14-19 days. Under the Migratory Bird Treaty Act it is illegal to harass, remove, or in any way disturb a nesting pair of swifts.

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The Swifts & Chimney at 415 West Washington 

In late summer and fall, swifts gather in large roost chimneys in preparation for their migration back to South America. The prominent chimney located at the historic industrial complex at 415 West Washington is a favorite roost with the swifts. In August 2018, 1,400 swifts were counted using the chimney at this site, which is the highest population of swifts recorded anywhere in the city of Ann Arbor. At dusk one can often witness the dramatic spectacle of the swifts funneling into the chimney in tornado-like flocks.

^{Video of Swifts at 415 West Washington (courtesy of CTN)}

_{Support Habitat Preservation by Supporting the Treeline}

This GivingTuesday, the Treeline Conservancy invites you to be more than an observer. Each donation helps us continue our critical work of creating a connected, vibrant urban trail that preserves habitats like the one our Chimney swifts call home. Your contribution will support preservation of this habitat and the continued development of the Treeline urban trail.

Every contribution, no matter its size, makes a difference. Whether you're inspired by the remarkable journey of these aerial acrobats or passionate about non-motorized infrastructure in our city, your support can help turn the Treeline from a vision into a living, breathing corridor of urban biodiversity.

Please consider making a donation in support of the Treeline.

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