Bats, Squirrels and Old-House Pests from Old Irving Park to the River

Is that a bat in the attic of an Old Irving Park house?

Old Irving Park, between Montrose and Addison from Pulaski to Cicero, has exactly the kind of houses bats like best: tall, wood-framed and full of small gaps. A survey by the Irving Park Historical Society counted several hundred buildings that predate 1894, many from the 1870s. Their steep roofs, turrets, dormers, clapboard siding and decorative trim have shrunk, shifted and been repainted for well over a century, opening cracks at the ridge, behind fascia boards, under the corner boards and where porches tie into walls. A bat needs a gap only about the width of a thumb.

Big brown bats are the species most often found in Chicago houses, and they are one of the few that will spend the winter inside a building rather than migrating to a cave, which is why some owners hear them in January. Little brown bats form summer colonies in attics too. Signs include small dark droppings that crumble into a glittery powder of insect parts, piled under the entry point or scattered across attic insulation, brownish rub marks around a gap in the trim and a stream of bats leaving at dusk on summer evenings. Droppings can grow a fungus that is harmful to breathe, so attic cleanup is done with protective gear.

Bats are protected, beneficial insect eaters, so the standard approach is exclusion, not killing. Timing matters. In Illinois, pups are born in late spring and cannot fly until midsummer, so a one-way exclusion device installed in June can trap flightless young inside. Wildlife specialists usually seal secondary gaps first, then install one-way devices from about August into fall and leave them in place until the colony is gone.

A railroad suburb named for Washington Irving

Major Noble bought a 160-acre farm here in 1843. In 1869 four investors from New York bought the land to create an upscale suburb and won a station on the Chicago and North Western line, which still serves the Irving Park Metra stop. Their planned name, Irvington, was already taken elsewhere in Illinois, so the town became Irving Park, after the author Washington Irving. John Gray, Cook County's first Republican sheriff, subdivided nearby Grayland around a Milwaukee Road station; his 1856 house on Grace Street is the oldest in the area. The township was annexed to Chicago in 1889, and residents formed their own park district in 1910, creating the neighborhood parks that still exist.

The Villa, between Pulaski, Addison and Avondale Avenue, followed from 1902 with Craftsman and Prairie-influenced houses, many by the firm Hatzfeld and Knox, and became a Chicago Landmark district in 1983. After World War II the Kennedy Expressway cut through the neighborhood and displaced many homes, and some large houses on Keystone, Kedvale and Keeler gave way to condominium buildings in the 1960s. Today 150-year-old frame houses, century-old bungalows and midcentury masonry often stand within a few blocks of each other, which is why pest problems here vary so much from one street to the next.

Squirrels on the eaves, raccoons in the chimneys

Irving Park's canopy is old and dense, and its squirrel population is large. Gray and fox squirrels run from parkway trees onto the eaves of Victorians and the low roofs of Villa houses, then chew through soft fascia, gable vent screens and the joints where dormers meet the main roof. They nest in attics in late winter and again in late summer. Their chewing on wiring is a real fire risk in older houses with mixed generations of electrical work, including old knob-and-tube runs that may still be live in some attics.

Raccoons are less frequent than squirrels but more destructive. They favor unused masonry chimneys on older homes and the space under large wraparound porches. Horner Park, a 54-acre park on the river at Montrose and California, had about 11 acres of riverbank restored from invasive thicket to native savanna in a project finished in 2018, with 128 native trees and 282 shrubs planted. That restored bank is good habitat, and raccoons and opossums use the river corridor to travel inland through alleys on the eastern blocks. A raccoon in a chimney in April almost always means young are present, which shapes how a specialist removes them.

Fieldstone, balloon frames and bungalow basements

Below the attic problems, the most common indoor complaint is house mice. Victorians in Old Irving Park often sit on fieldstone or soft early brick foundations that have been patched many times, and the patches pull away from the original masonry. Villa houses and the neighborhood's later bungalows have deep basements with steel windows, coal-chute openings and utility lines added over decades. Each is a fall entry point. In a balloon-framed house, where wall cavities run uninterrupted from sill to rafters, a mouse that gets into the basement can climb inside the wall all the way to the attic, which is why owners sometimes hear mice overhead before they find droppings in the kitchen.

Damp corners in those basements support house centipedes and silverfish, and older floor drains can bring up an occasional American cockroach in late summer. Carpenter ants are a concern specific to the frame houses. They excavate wet wood in porch columns, window sills and the sill plates under rear additions, and finding large black ants indoors in late winter or early spring often means a nest inside the structure rather than one outside. Fixing the moisture source matters as much as treating the colony.

Two-flats, apartment buildings and 1960s condos

Not every Irving Park building is a Victorian. Early twentieth-century apartment buildings went up north of Irving Park Road, brick two-flats line many blocks in Independence Park and near the Kennedy, and the 1960s condominium buildings on Keystone, Kedvale and Keeler are multi-unit masonry with shared basements and trash areas. These buildings see few bats but more German cockroaches, which move between kitchens through plumbing walls, and more mice traveling through common basements in fall. Garden units in the older apartment buildings north of Irving Park Road tend to report mice first, because they sit beside the boiler room and laundry where mice nest over winter.

The approach in these buildings is closer to apartment work than house work. Treating all units on a shared stack together, sealing pipe gaps under sinks and keeping garbage rooms clean matter more than roofline repairs. Condo associations usually coordinate common-area treatment, so owners should tell the board when they see roaches so neighboring units can be checked at the same time. In the industrial edges near Kilbourn Park and the rail lines, Norway rats along tracks and alley garages add another layer to the list.

Kilbourn Park, Avondale Gardens and the rail edges

South of Addison, the western part of the community area reaches down to Belmont Avenue, and its character changes. Kilbourn Park, between Milwaukee and Belmont from the Union Pacific Northwest tracks to Cicero, and Avondale Gardens, sometimes called Merchant Park or South Old Irving Park, between Addison and Belmont east of the tracks, mix brick bungalows, two-flats and frame houses with rail lines and older industrial land. These blocks feel more like Avondale than like the Victorian streets to the north.

Here the pest list shifts from the roof to the ground. Rail embankments give Norway rats long, undisturbed burrowing strips beside alleys, and detached garages along those alleys are the usual burrow sites. Raccoons and opossums travel the tracks at night. Indoors, two-flat basements carry mice in fall and shared plumbing carries German cockroaches year-round. Anchored bait stations along garages that back toward the tracks and sealed garage door bottoms are the standard first steps.

Calendar for an old-house neighborhood

Many of the problems in Irving Park are tied to animal breeding seasons, so knowing the calendar helps owners book the right work at the right time and avoid paying twice. The months are approximate, and a mild winter or late spring can move them by a few weeks. Insect activity follows temperature, while wildlife follows the breeding cycle. Booking a bat inspection in spring, before the colony settles, gives a specialist time to plan the August exclusion.

• January and February: hibernating big brown bats sometimes wake and appear indoors; squirrels pick attic nest sites.
• March and April: squirrel and raccoon litters arrive; winged carpenter ants indoors point to nests in the walls.
• May and June: bat maternity colonies form and pups are born; do not seal bat entries now.
• July: pups begin to fly; inspect and seal secondary gaps while the colony is still present.
• August to October: the main window for one-way bat exclusion; squirrels raise a second litter.
• October and November: mice enter through foundations and climb balloon-framed walls.

Prevention steps for Victorians and Villa houses

Most of these steps involve the building envelope, because that is where Irving Park's pests get in. Owners in the Villa and other designated areas should plan visible exterior repairs with materials that suit the original house and avoid quick fixes such as expanding foam on painted trim, which squirrels chew through and which looks out of place on a historic facade. Painted copper or galvanized mesh blends far better.

• Walk the house at dusk in July to see where bats exit, then note those spots for a specialist.
• Cap every chimney, including flues no longer in use.
• Replace window screen on gable vents with heavy-gauge metal mesh.
• Repair or replace soft fascia, corner boards and dormer flashing before fall.
• Trim limbs six to eight feet back from roofs, turrets and dormers.
• Repoint fieldstone and early brick foundations where mortar has failed.
• Fix gutters and porch roofs that keep columns, sills and sill plates wet.
• In condo and two-flat buildings, treat every unit on a shared stack at once.

What a wildlife or pest inspection covers here

Because so many problems start at the roof, a thorough Irving Park inspection usually involves a tall ladder or lift as well as a walk through the attic and basement. A wildlife specialist checks every potential gap, confirms the species from droppings and damage and, for bats, counts exit points and notes whether the colony is a summer maternity group. The estimate typically covers exclusion devices, sealing materials and any cleanup of droppings or soiled insulation.

The Villa is a Chicago Landmark district, so substantial visible exterior changes generally go through city review. Small exclusion work rarely raises an issue, but replacing trim or altering a roofline should be checked first. If anyone wakes to find a bat in a bedroom, keep the bat contained if it can be done safely and contact a doctor or the health department, since bats can carry rabies; that step comes before any exclusion work. Same-day response is often available for a bat or raccoon inside living space.