Ice dams and squirrels share the same weak spot
In Wisconsin the eave takes a beating every year. Heat escaping through the attic melts snow on the upper roof, the water runs down to the cold overhang and refreezes, and the ridge of ice that forms backs meltwater under the shingles and into the fascia and soffit. That wood goes soft, then splits, then lifts. a squirrel is opportunistic rather than powerful. It cannot open sound, dry, well fastened trim quickly, but it can turn a lifted soffit edge into an entry in an afternoon. That is why so many entries appear at the same corners where you saw icicles hanging in February. The fix works on both problems at once. Rebuild the damaged board rather than covering it with trim coil, back it with metal, and then deal with why the ice formed: attic insulation depth and ventilation. Homeowners who do only the wildlife half find themselves repeating this in two winters, because the eave keeps producing the same soft edge.
A month by month picture for Wisconsin homeowners
October is the month that saves you money. Mast is dropping, animals are caching rather than denning, and the roof edge is dry and accessible. Repairs made now happen with nothing living behind the wood. November through March is the busy stretch. Cold at the 13F median winter low in our Wisconsin city data drives flying squirrels and red squirrels indoors in groups, and Penn State Extension dates the first breeding period to mid December or early January. From February onward, treat every attic as potentially holding young until someone has looked. Late April through May is the clean window: first litters are mobile, the second breeding cycle has not begun, and the eave is finally free of snow. June restarts the calendar, so July and August work needs the same pup check that February work does. If you can schedule around the weather, do carpentry in spring or fall and let removal happen whenever the animals force the issue.
Milwaukee duplexes and shared soffit runs
Dense older housing changes the geometry of the job. In Milwaukee, Racine, and Kenosha neighborhoods, duplexes and closely spaced houses often carry one continuous soffit run along the whole side of the building, and mature street trees put branches within easy jumping distance of the roof. That means squirrels do not really enter a unit. They enter a building and then drop into whichever ceiling bay is open. Patching the hole above the upstairs bedroom frequently just moves the noise to the other side of the wall, which is how owners end up paying three times for a job that should have been done once. The approach that works is to treat the roofline as a single system. Inspect the full perimeter, list every opening, close them all in metal in one pass, and clear the tree branches feeding the roof. For a two unit building, coordinate access to both attics before the work starts, because the crew will need to see both sides to know whether the space is empty.
How to tell what is living up there
Start with the hour on the clock. Activity that peaks around sunrise and again in late afternoon means gray or fox squirrels, the daytime animals, usually one adult holding a den. Heavy footfalls that sound like something rolling belong in this group. Strictly nocturnal noise, lighter and more scattered, points at flying squirrels. They arrive as a group and huddle together when temperatures drop, which in Green Bay or Madison in January is most nights. Because they are quiet by day, homeowners often live with them for a season before identifying them correctly. Red squirrels sit in between. They are small, extremely loud for their size, and they do the most obvious insulation damage, tearing batts apart for nesting and stuffing cavities with cone scales. They also use openings too small for a fox squirrel, so an inspection that checks only the obvious gaps can miss them. Tell the operator what you hear and when, and the species question is usually settled before anyone climbs a ladder.
What happens to the attic after they leave
Removal is the middle of the project. The wiring comes first afterward, because gnawing strips cable insulation and the damage sits where nobody looks. If a nest was active near a wiring run, have an electrician check it before the attic gets closed up again. Insulation is next and it has a direct dollar value in this climate. Soaked and soiled batts do not recover their rating, and losing R value in a state with winter lows near 13F shows up on every heating bill until it is fixed. Get the square footage and the target R value written into the quote instead of accepting a line that just says cleanup. The last piece is odor. A used den smells like a den, and that scent tells the next squirrel working the block that the space was suitable. Disinfection reduces the signal, and metal on the roof edge makes the message moot, since nothing can act on it.
Comparing quotes without getting talked into anything
Set the two documents down and compare entry counts before prices. A company that lists one opening on an older duplex either got lucky or never walked the roof. Ask each to point out the specific spots from the ground, and the gap usually explains itself. Read the material descriptions next. You want steel mesh, aluminum flashing, or replacement wood with metal behind it. Foam, sealant, plastic vent screen, and paint will not survive a freeze and thaw cycle, let alone a determined animal. Third, ask about the calendar. An operator who mentions checking for young without being asked has done this in February. Fourth, confirm whether the quote assumes one animal or a group, since a nocturnal colony changes the number of visits. Finally, ask whether attic cleanup and insulation replacement are included or extra, because that is usually where two prices that looked comparable turn out to be describing very different jobs.