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Blog Nature

Bears, Burls, and Butter-butts

After grazing on some winter grass, Mimi bear seemed to be headed for the culvert pipe attraction in her enclosure to slip inside for a nap. Gus bear was already engaged. With a sidelong glance at the slumbering male bear, Mimi slinked off to greener pastures.

Bear sleeping
Gus in slumber.
Two bears, one sleeping and one looking back
Mimi sends a sideways glance towards a relaxing Gus.
Two bears, one sleeping and one walking.
She moves on.

Recently, Ranger Brooke found a small piece of pine branch with a growth attached. She asked me what I thought it was. I reasoned it a gall. It was about 3” lengthwise, about the same size and shape as a blackberry knot gall (a blackberry bush’s reaction to tiny wasps laying eggs in its stems – see here – More Galls). But this object was very hard. Galls can typically be cut open with a penknife. That didn’t work here.

Human hand holding wooden
Is this a gall?

I suggested we take the gall, or whatever it was, to the Exhibits Shop and see if we could have it cut down the middle on a band saw. If it was a gall it would have insect larvae inside.

Exhibits prototyper, KJ, gleefully offered to cut open the object. Inside, it was all wood. It was a burl.

Solid wood burl being held by human hand.
Solid wood.
Solid wood burl being held by human hand.
Besides the straight lines caused by the saw, you can see circular grain growth contrary to the straight grain of the original branch.

According to Merriam-Webster online dictionary, a burl is: a hard woody often flattened hemispherical outgrowth on a tree.

Another online dictionary defines a burl as: A rounded knotty growth on a tree, giving an attractive figure when polished and used especially for handcrafted objects and veneers.

In the UK you would refer to the growth as a bur or burr.

Burls are a tree’s reaction to an injury, virus or fungal infection, or insect infestation. The burl itself is not diseased nor does it contain diseased or contagious material. It contains bud material that hasn’t grown into branches or foliage but instead has grown into itself. It’s all wood inside, gnarly, twisted wood.

Burl on the side of pine tree
Burl at the base of loblolly pine.

Because of their intricate, twisted grain, they’re valued by craftspeople for woodworking as veneers, insets, instruments, and implements.

Should you remove a burl from a living tree? Probably not. The tree is in no way harmed by the presence of a burl. However, if you cut out a burl you’re removing a living portion of the tree, exposing it to outside damage that otherwise would not occur.

Yellow-rumped warblers, a.k.a., myrtle warblers, a.k.a., butter-butts, have been ravaging the wax myrtle fruit all around campus. When the weather gets cold and insects become scarce the largely insectivorous warblers turn their attention toward wax myrtle fruit. If you stand still near one of these fruit-laden shrubs you can watch the birds gorge themselves with the waxy fruit.

Two birds in a tree
Two butter-butts attack wax myrtle fruit.
Bird eats fruit on trees
Reaching for the fruit.
Bird eats
Gulping it down.
7 yellow-bellied warblers in a grouping of trees
There are seven warblers in this picture.
Bird upside down to reach fruit
Acrobatic birds.
Bird eats
The fruit has a large hard seed inside a thin waxy coating.

If the cold, inclement weather persists, the birds make quick work of the fruit and move on in search of more. If you spot a feeding frenzy of these little parulids, fruit-eating birds, appreciate it while you can. Once the fruit is gone, so are they.

Butter-butts help propagate wax myrtle shrubs. The waxy coating on the fruit prevents water from entering the seed. In order to germinate, the wax coating must be removed. By swallowing the fruit whole the bird’s digestive system does the work of extracting the wax, and out comes a seed ready to grow into a wax myrtle shrub, or tree. Well, almost ready. The seeds need to be cold stratified for about 90 days before they’ll sprout, but most of the work is done.