Original Finding
Tube Feeders Have a Body-Mass Ceiling Near 44 Grams
Grouping our 73 feeder-using species by the feeder types they use produces a sharp discontinuity: tube users have a median mass of 15.5 g and stop dead at 44 g, while platform users run to 468 g with no ceiling at all.
The short answer
- The heaviest species in our matrix recorded as a tube feeder user is the Rose-breasted Grosbeak, at about 44 g (1.6 oz).
- 25 of 73 feeder-using species, 34%, are heavier than that. Not one of them is listed as a tube user.
- Median tube user: 15.5 g. Median platform user: 44.5 g. The platform audience is roughly 2.9 times heavier.
- The practical reading: a tube feeder is not a general purpose feeder. It is a small-bird instrument, and buying one first is buying the narrow end of the range.
Method at a glance
- Question
- Does feeder type sort feeder birds by body mass, and if so, where are the edges?
- Data
- Feeder bird trait matrix, 78 species, 73 of them feeder-using
- Method
- Group species by normalized feeder type, compare mass distributions
- Mass measure
- Midpoint of the published range on each species profile
- Reproducible
- Yes, from the published CSV
- Type
- Analysis of compiled data, not field observation
What we did#
Each of our 78 species profiles carries an "At a glance" block naming the feeder types that species uses and its published mass range. We extracted both into a structured matrix, normalizing free-text feeder descriptions into nine controlled terms, then grouped species by term and compared the mass distributions. The extraction rules are on the methods page and the script is in the site repository, so the whole thing regenerates from the published pages.
The result#
| Feeder type | Species | Median mass | Lightest | Heaviest |
|---|---|---|---|---|
| Platform or tray | 46 | 44.5 g | Chipping Sparrow (13.5 g) | American Crow (468 g) |
| Suet cage | 25 | 24 g | Bushtit (5.5 g) | Pileated Woodpecker (300 g) |
| Ground or scattered | 25 | 42.5 g | Chipping Sparrow (13.5 g) | American Crow (468 g) |
| Hopper feeder | 19 | 42 g | Pygmy Nuthatch (10.2 g) | Common Grackle (108 g) |
| Tube feeder | 19 | 15.5 g | Lesser Goldfinch (9.8 g) | Rose-breasted Grosbeak (44 g) |
| Peanut feeder | 11 | 24.5 g | Carolina Chickadee (10 g) | Steller's Jay (120 g) |
| Nectar feeder | 9 | 3.6 g | Costa's Hummingbird (3 g) | Gray Catbird (39.5 g) |
| Dish, cup or jelly feeder | 9 | 30 g | Bewick's Wren (10 g) | Northern Mockingbird (51.5 g) |
| Nyjer or finch feeder | 3 | 15 g | Lesser Goldfinch (9.8 g) | American Goldfinch (15.5 g) |
Two things stand out. The first is the ordering, which is not surprising in itself: nectar and nyjer feeders serve the smallest birds, platforms and ground feeding serve the largest. The second is the ceiling, which is sharper than a gentle preference gradient would predict. The heaviest tube users in the matrix are Rose-breasted Grosbeak (44 g), Purple Finch (25 g), Downy Woodpecker (24.5 g), White-breasted Nuthatch (24 g), Tufted Titmouse (22 g), House Finch (21.5 g), Oak Titmouse (16 g), Painted Bunting (16 g). Above 44 g the tube list simply ends.
The species above the line#
These are the 25 feeder-using species heavier than the heaviest recorded tube user. Read down the right hand column: platforms, ground, hoppers and suet cages, over and over.
| Species | Mass | Feeder types it does use |
|---|---|---|
| American Crow | 468 g | Ground or scattered, Platform or tray |
| Pileated Woodpecker | 300 g | Suet cage |
| Black-billed Magpie | 177.5 g | Ground or scattered, Platform or tray, Suet cage |
| Eurasian Collared-Dove | 160 g | Ground or scattered, Platform or tray |
| Northern Flicker | 135 g | Ground or scattered, Platform or tray, Suet cage |
| Clark's Nutcracker | 133.5 g | Ground or scattered, Platform or tray, Suet cage |
| Mourning Dove | 133 g | Ground or scattered, Platform or tray |
| Steller's Jay | 120 g | Peanut feeder, Platform or tray, Suet cage |
| Common Grackle | 108 g | Ground or scattered, Hopper feeder, Platform or tray |
| Blue Jay | 85 g | Hopper feeder, Peanut feeder, Platform or tray |
| California Scrub-Jay | 85 g | Ground or scattered, Peanut feeder, Platform or tray |
| American Robin | 81 g | Ground or scattered, Platform or tray |
| European Starling | 78 g | Platform or tray, Suet cage |
| Acorn Woodpecker | 77.5 g | Platform or tray, Suet cage |
| Brown Thrasher | 75 g | Ground or scattered, Platform or tray |
| Red-bellied Woodpecker | 73.5 g | Hopper feeder, Peanut feeder, Platform or tray, Suet cage |
| Red-headed Woodpecker | 73.5 g | Platform or tray, Suet cage |
| Canada Jay | 71 g | Platform or tray, Suet cage |
| Hairy Woodpecker | 67.5 g | Hopper feeder, Peanut feeder, Suet cage |
| Pine Grosbeak | 67 g | Platform or tray |
| Evening Grosbeak | 63.5 g | Hopper feeder, Platform or tray |
| Red-winged Blackbird | 54.5 g | Ground or scattered, Hopper feeder, Platform or tray |
| Northern Mockingbird | 51.5 g | Dish, cup or jelly feeder, Platform or tray |
| Brown-headed Cowbird | 46 g | Ground or scattered, Hopper feeder, Platform or tray |
| Northern Cardinal | 45 g | Hopper feeder, Platform or tray |
Why the ceiling is where it is#
The mechanism is not mysterious, and the number matches it. A tube feeder perch is a short dowel, typically 1.5 to 3 in (4 to 8 cm) of usable length, projecting from a vertical cylinder. Using it requires a bird to balance its whole mass on a perch shorter than its own body, with nothing to brace against and no room to spread its feet. Birds built for clinging and hanging manage this at any size in their range. Birds built for standing on branches and ground do not, and the heavier the bird the worse the leverage gets.
So the ceiling is really a statement about posture and foot structure, with mass as the proxy that happens to be measurable. It is a good proxy precisely because the exceptions run in the direction you would expect: woodpeckers and nuthatches, which cling by design, sit high in the tube list for their weight.
This is also why a tube feeder with a tray attached behaves like a different feeder. The tray converts the tube from a perch problem into a platform, which is exactly what the ceiling predicts would fix it. If you already own tubes, a $10 seed tray is a bigger upgrade than a second tube.
An independent check#
A derived result is worth more if something written independently agrees with it. Our Northern Cardinal profile was written long before this matrix existed, and it says cardinals "use narrow tube perches badly and often not at all" and that a flat surface is the single change that brings them in. The cardinal's mass midpoint is 45 g. The ceiling derived from the matrix, with no knowledge of that sentence, is 44 g.
The cardinal lands one gram over the line. That is a coincidence in its precision but not in its direction, and it is the kind of check that makes a compiled dataset worth compiling: a qualitative judgment made species by species, and a threshold computed across the whole set, arriving at the same place by different routes.
What this does not show#
Three limits, stated plainly.
This is compiled data, not observation. The matrix encodes what our profiles say, which comes from published institutional sources. If those sources under-report a heavy bird occasionally using a tube, our ceiling is too low. The Feeder Log exists partly to test exactly this, and it is free to contradict us.
"Uses" is binary here, and use is really a frequency. A species that visits a tube once a season and one that lives on it are both a yes. A properly weighted version of this analysis needs visit-rate data, which is what the Feeder Log is collecting.
The mass midpoint hides sexual dimorphism and regional variation. For most feeder species the range is narrow enough not to matter. For a few it is not.
Do not read this as "tube feeders are bad". They are efficient, they keep seed dry, and they are excellent at what they do. The finding is about range, not quality: a tube serves the light half of the community well and the heavy half not at all.
What to do with it#
If you are buying your first feeder and want the widest range of birds, the mass distribution says start with a flat surface, not a tube. That conclusion is reinforced from a completely different angle by our feeder coverage analysis, which asks which small set of feeders reaches the most species and also puts the platform first.
If you already run tubes and want more species, the cheapest move is a tray under one of them, then a suet cage. See feeder types for how each design behaves and placement for where to put it.