DIY Project
DIY Window Feeder
A window feeder puts a chickadee 18 inches from your face. The build is easy; the parts people get wrong are the suction cups and the distance from the glass.
The short answer
- Assume no more than about 2 pounds (0.9 kg) of real holding power per good 2 inch (50 mm) suction cup outdoors, and use four cups on a feeder that weighs 2 pounds (0.9 kg) loaded.
- Add a backup: a screw hook in the window frame and a short wire lanyard to the feeder, so a failed cup means a hanging feeder rather than a broken one.
- Mount it within 3 feet (1 m) of the glass. At that distance a startled bird cannot build up enough speed to be badly hurt if it hits.
- Drill acrylic with a slow speed, backed by scrap wood, and drill every mounting hole oversize so the sheet can expand without cracking.
- Expect 3 to 6 years from a 1/4 inch (6 mm) acrylic tray. The cups fail long before the acrylic does, usually in the first cold snap.
This is a five-piece acrylic tray, 12 inches (30 cm) wide and 5 inches (13 cm) deep, with an 8 inch (20 cm) back panel carrying four suction cups. It holds about 2 cups of seed, drains through six drilled holes, and comes off the glass in one piece for cleaning.
Build time is about 90 minutes if you are cementing the joints, plus overnight for the cement to reach full strength.
Two things below matter more than the woodwork-equivalent details: how much a suction cup will really hold once it is cold and dirty, and why the feeder has to be right against the glass rather than a few feet out.
Cut list#
| Part | Qty | Material | Finished size |
|---|---|---|---|
| Back panel | 1 | Clear acrylic, 1/4 in (6 mm) | 12 x 8 in (305 x 203 mm) |
| Floor | 1 | Clear acrylic, 1/8 in (3 mm) | 12 x 5 in (305 x 127 mm) |
| Front lip | 1 | Clear acrylic, 1/8 in (3 mm) | 12 x 1-1/2 in (305 x 38 mm) |
| Side wall | 2 | Clear acrylic, 1/8 in (3 mm) | 5 x 3 in (127 x 76 mm) |
| Suction cups | 4 | Rubber, with a threaded or mushroom stud | 2 in (50 mm) face diameter |
| Backup hanger | 1 | Stainless screw hook plus coated wire | 6 in (15 cm) of wire |
Hardware: acrylic solvent cement and an applicator, plus four stainless washers and nuts if your cups use threaded studs.
The side walls are 3 inches (76 mm) tall at the back and can be cut down to 1-1/2 inches (38 mm) at the front for a sloped profile. That is cosmetic. Square walls work fine.
Tools#
- Fine-tooth saw suitable for plastics, or a scoring knife and a straightedge for the 1/8 inch (3 mm) sheet.
- Drill with 3/16 inch (5 mm) and 5/16 inch (8 mm) bits.
- Fine metal file and 220-grit sandpaper.
- Solvent cement applicator, or a small syringe.
- Masking tape, square, marker, safety glasses.
Leave the protective film on both faces of the acrylic until the last possible moment. It stops the surface from scratching while you cut and drill, and marker lines wipe off it cleanly.
Cutting and drilling acrylic without cracking it#
Acrylic breaks for predictable reasons: the bit grabs, the sheet is unsupported, or the hole is too close to an edge.
Score-and-snap the 1/8 inch (3 mm) sheet with a plastic scoring knife: eight to ten passes along a clamped straightedge, then snap it over the edge of a bench. For 1/4 inch (6 mm), saw it with the sheet supported flat and the blade running at moderate speed.
Drill on a scrap wood backer, at low speed, with light steady pressure. Back the bit out to clear chips. Keep every hole at least 1/2 inch (13 mm) from an edge.
File and sand every cut edge until it is smooth to a bare finger. Freshly cut acrylic has a fine, brittle edge that chips into slivers, and the birds using this feeder will be standing on it.
Smooth every edge before it goes up
Any cut plastic or metal edge on a feeder can cut a foot or catch a bill. Run a file along all four cut edges of each piece and finish with 220-grit until nothing catches on a fingertip pulled slowly along it. This takes ten minutes and is not optional.
Assembly#
1. Dry fit. Tape the floor, lip and side walls into position against the back panel. Check for square and for gaps. Solvent cement fills nothing.
2. Cement the tray. Hold each joint tight and run the applicator along the seam. Capillary action pulls the solvent through. Do the floor to the back panel first, then the sides, then the front lip. Leave it undisturbed for at least an hour, and overnight before loading it.
3. Drill the drain holes. Six 3/16 inch (5 mm) holes through the floor, spaced evenly, at least 1/2 inch (13 mm) from any joint. Drainage is what keeps seed from souring in a shallow tray after rain.
4. Drill the suction cup holes. Four 5/16 inch (8 mm) holes in the back panel, one near each corner, 3/4 inch (19 mm) in from the edges. Oversize holes let the acrylic move with temperature and stop the studs from stressing the sheet.
5. Fit the cups and the backup. Push the studs through and secure with a stainless washer and nut. Then drill one more hole in the top edge of the back panel for the backup wire.
Suction cups: what they really hold#
Package ratings are pull tests on clean, dry, room-temperature glass. Your window is none of those things by November.
Three things reduce holding power: cold, which stiffens the rubber and lets air seep past the rim; contamination, since pollen, dust and window film all break the seal; and age, because UV hardens rubber within a couple of seasons.
Work to about 2 pounds (0.9 kg) per 2 inch (50 mm) cup as a real-world figure and build in a wide margin. The tray described here weighs roughly 1 pound (0.45 kg) empty and about 2 pounds (0.9 kg) with a cup of seed and a couple of birds on it. Four cups gives roughly a four-to-one margin, which is the right amount for something hanging over a walkway.
The backup hanger is the part people skip
Drive a small stainless screw hook into the window frame above the feeder and run a 6 inch (15 cm) coated wire from it to a hole in the top edge of the back panel. Keep the wire short and taut with no loose loop a bird could catch a foot in. When a cup lets go at 20°F (-7°C), the feeder swings and stays put instead of hitting the ground.
Re-seat the cups monthly: peel each one off, wipe both faces with rubbing alcohol, warm the cup in your hand, wet the rim with a drop of water, and press it back with a firm push from the center outward.
Why 3 feet (1 m) from the glass is the safe distance#
Window collisions kill birds because of speed, not because of glass. A bird that strikes a window at full flight speed usually dies; a bird that bumps it after a startled hop rarely does.
A feeder mounted on the glass, or within 3 feet (1 m) of it, means every takeoff is from a standing start. There is no runway. The bird also learns the window is a solid boundary because it perches beside it many times a day.
The dangerous zone is the middle distance. A feeder 10 or 15 feet (3 to 4.6 m) out gives a fleeing bird room to accelerate straight into a reflection of sky and trees. The full explanation, including the other safe option of moving feeders beyond 30 feet (9 m), is in feeders and windows: the one foot / thirty foot rule, and the treatments that make glass visible are in preventing window strikes.
Which window matters too. North and east faces reflect less sky than a west-facing window in afternoon sun. If your window already produces strikes, add exterior markers before adding a feeder.
Filling, cleaning and who shows up#
Fill it shallow: half an inch (13 mm) of seed across the tray, no more. A small tray with a deep pile of seed goes damp underneath before it gets eaten.
Sunflower hearts are the best choice here because there are no hulls to blow onto the sill. Black oil sunflower works if you accept sweeping. Skip mixes heavy in filler seed, which get kicked out and pile up below.
Take the whole tray down weekly, tip it out, wash it in hot soapy water, rinse and dry fully before refilling. Never use an abrasive pad or ammonia-based glass cleaner on acrylic: both haze the surface permanently. The disinfecting routine is in how to clean a bird feeder.
Never clean acrylic with glass cleaner
Ammonia-based cleaners and abrasive pads craze and haze acrylic permanently, and a hazed window feeder is a window feeder you cannot see through. Hot water, dish soap and a soft cloth are all it needs. Rinse well and dry it fully before refilling.
Expect black-capped chickadees first, usually within days, then house finches, titmice and nuthatches. Cardinals will use a window tray but want the wider 5 inch (13 cm) floor and often feed at dusk. If nothing arrives after two weeks, the checklist in why are no birds coming to my feeder applies.
One thing to fix indoors: keep cats off the sill directly behind the feeder. A cat visible through the glass a foot away deters most birds even though it cannot reach them.
Lifespan and common mistakes#
Cast acrylic lasts 5 to 10 years outdoors before yellowing and surface crazing set in; the thinner tray pieces and the cemented joints usually give up around year 3 to 6 in a freeze-thaw climate. Suction cups are the true consumable and are worth replacing every two years whether or not they have failed.
- Thin back panel. A flexing panel peels cups off.
- Undersized mounting holes. Acrylic expands. Drill them oversize.
- No drain holes. A tray that holds water holds moldy seed.
- Filling it deep. Half an inch (13 mm) is plenty.
- Skipping the backup wire. One cold night is all it takes.
- Mounting it 10 feet (3 m) from the glass on a pole instead. That is the worst possible distance. Either put it on the window or move it well past 30 feet (9 m), as covered in window feeders.
Frequently asked questions#
How much weight can a window feeder suction cup hold?
Far less than the number on the package, which is measured on clean, warm, dry glass. Outdoors, plan on about 2 pounds (0.9 kg) per 2 inch (50 mm) cup and use four of them. Cold stiffens the rubber, dirt and pollen break the seal, and both effects arrive together in fall.
How far from the window should a window feeder be?
Within 3 feet (1 m) of the glass, and mounting it directly on the glass is ideal. A bird taking off from that close cannot reach a dangerous speed before it hits. The dangerous zone is the middle distance, roughly 3 to 30 feet (1 to 9 m), where birds fly fast enough to be killed.
Will a window feeder cause window strikes?
Correctly placed, it reduces them. A feeder stuck to the glass makes the window an obvious solid object rather than an invisible reflection, and any collision happens at low speed. A feeder placed 15 feet (4.6 m) from a window is the setup that causes strikes.
What thickness of acrylic should I use?
Quarter inch (6 mm) for the back panel that carries the suction cups, and 1/8 inch (3 mm) is adequate for the tray floor and walls. Thinner back panels flex, and flex peels a suction cup off the glass from one edge inward.
How do I stop suction cups from falling off in winter?
Clean both the glass and the cup faces with rubbing alcohol, warm the cups in your hands before pressing them on, and re-seat them monthly. Wet the rim of each cup with a drop of water first. Even then, expect one to let go during a hard freeze, which is why the backup hanger matters.
Can squirrels reach a window feeder?
Usually yes, if there is a sill, frame, siding seam or nearby branch to climb. Smooth glass alone stops them, but very few windows are surrounded by nothing but glass. A second-story window with clear siding below is the closest thing to squirrel-proof.