One concern I have is how much they whip around in the wind!
I have found that any sort of birdhouse is more likely to be used when it is firmly secured to something stable.
If a bird is the type to build in a tree hollow that a gourd simulates, they're NOT a branch-nest-builder. Therefore: they're accustomed to very stable and protected nests. Not ones that bounce around in the wind, like a nest at the junction of a branch might.
Also: Keep in mind the diameter of the hole, and the internal size of the gourd.
Smaller birds that will nest inside something gourd-sized likely will not need a 2-inch diameter hole. Choosing the right hole size will change what birds are attracted to the home in the first place. With a very large hole, large birds (like starlings, crows, and small falcons) can shove their head in and harass the nest.
Smaller birds can nest through larger holes, but larger birds cannot access smaller holes.
Entrance hole sizes for various birds:
1.25 inches: Wren, Woodpecker, Warbler, Nuthatches, Chickadee
1.5 inches: Tree Swallow, Bluebird
1.75 inches: House Sparrow
2 inches: House Finch
2.5 inches: Purple Martin, Flicker
3 inches: Kestrel (Sparrowhawk)
Additionally, birds will prefer different /spaces/ to build their nest in, and won't nest in a gourd that doesn't have enough room between the 'floor' and the entrance.
Wrens, Warblers, Tree Swallows, Finches, and Flickers only need about 4 inches of depth to build a nest.
While Woodpeckers, Nuthatches, House Sparrows, Chickadees, and Bluebirds need at least 6 inches.
At a glance, the holes on Matt's gourds may be too close to the 'floor' for most birds.
Purple Martins and Bluebirds prefer birdhouses in open areas: Like, something mounted on a pole to simulate a single dead tree in the middle of a field.
Most other birds prefer concealed areas that help camouflage their nesting area, with branches, roofs, or other overhangs to shield them from view.
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Too Long, Didn't Read:
Stuff that makes small birds who may nest in gourds feel unsafe:
- Too-big hole entrances
- Their house whipping around in the wind
- Their house out in the open where everyone can see them
- Not enough building room between the floor and the door.