The Congress Avenue Bridge is home to the largest urban bat colony in North America.

If you happen to be in Austin in late spring, summer or early fall, don't miss the nightly spectacle of some 1.5 million migratory free-tail bats heading out in search of supper from their daytime refuge beneath the Congress Avenue Bridge.

July and August are generally the best months for bat-viewing in Austin, but these insectivorous creatures typically arrive from their winter home in Mexico around late March and stay through the end of October.

The Austin American-Statesman at 305 S. Congress Ave. offers a public viewing area and free parking for bat-watchers after 6 p.m., as well as a telephone hotline for updates on expected flight times (call 512-416-5700, ext. 3636). The bats also may be viewed from pedestrian walkways on the bridge, from the Town Lake Hike and Bike Trail and from public patios at various lakeside restaurants and hotels.

For an even closer vantage point, nightly bat-watching excursions are offered in season by Capital Cruises (www.capitalcruises.com) and the Lone Star Riverboat (www.lonestarriverboat.com), both departing about half an hour before sunset from docks on the south shore between the Congress Avenue Bridge and the First Street Bridge.