Woodpeckers save trees?! (With study)

"Inadvertently introduced into North America in the 1990s, the invasive emerald ash borer has been spreading across the Great Lakes Region resulting in widespread ash tree death. Native woodpeckers and other bark-foraging insectivores represent one of the few potential natural predators of EAB in the U.S. This study combines observational and destructive tree harvesting approaches to assess bark-foraging bird predation on EAB larvae in a deciduous forest of central Ohio. Results of the observational study show that in an EAB impacted forest, bark-foraging birds forage more heavily on ash trees than non-ash trees, and that they forage preferentially on ash trees that exhibit canopy decline symptoms relative those with healthy canopies. These patterns were further supported by the destructive sampling of 46 ash trees wherein predation by bark-foragers significantly reduced tree-level EAB densities by upwards of 85%. Bark-foraging predation intensity increased with increased EAB infestation levels, with bark-foragers harvesting 45% of EAB in trees with thinning canopies compared to 22% in ash trees with healthy canopies. Woodpeckers harvest EAB in a density-dependent pattern that could contribute to population control. Despite bark-forager predation, EAB had a high likelihood of successfully emerging from the heavily infested ash trees (30% or 35 EAB per m2)"
"Bark-foragers respond to EAB infestation and may thus potentially help regulate EAB populations and their spread in a mixed deciduous forest. We suggest that maintaining snags and nesting sites during and after forest pest outbreaks may enhance populations of bark-foraging bird species and, thus, their biological control of pest insects in temperate deciduous forests."

What woodpeckers like: standing deadwood trees (nesting + food), nesting boxes, food during the winter months (woodpeckers dine mostly on insects, but will also eat acorns, nuts, fruit, sap, berries and pine seeds). There isn't much you can do beyond renovating your property into a food forest/permaculture landscape.

https://www.fs.fed.us/nrs/pubs/jrnl/2014/nrs_2014_flower_001.pdf .... "Native bark-foraging birds preferentially forage in infected ash (Fraxinus spp.) and prove effective predators of the invasive emerald ash borer (Agrilus planipennis Fairmaire)"
DON'T USE SUET; causes cardiovascular disease.

I wonder if crickets, or cricket meal, as part of an ethically sourced suet block, would help. I mean, they are insectivores, after all.

As to the study, I take it that the title of the thread means trees in general; I have usually noticed that once woodpeckers are drawn to a tree, the infestation and subsequent search by peckers for tasty insects kills the individual. I like the idea, though, that perhaps an infestation in one tree could foster a new generation of peckers that would keep the population of borers down in the whole forest, perhaps even limiting their spread.

-CK

That's really cool! I'm aware of a couple borer insects really having an impact on certain tree populations like the pine bark borer and the ash borer as you mentioned. I like it when I see examples of nature finding a balance when something like an invasive species starts getting out of control. I love woodpeckers, I think they're really entertaining to watch and if I hear one in the woods I'll stop and listen for a few minutes. It's relatively easy to identify what kind of woodpecker activity is going on by the size and shape of the hole in a tree. Very large holes are generally nesting holes, and the size varies based on the species making the hole, but they are easy to differentiate from foraging holes and drumming holes. Here's a couple images of nesting holes.








Foraging holes often go in a row, sideways or vertically or anywhere in between, as the woodpecker bores into a tunnel made by an insect or grub to find the tasty meal. Drumming holes look like foraging holes, and can be a single hole or a cluster, but generally aren't found in little rows like foraging holes. Here's a few images of foraging holes.

Chris Kott wrote:

As to the study, I take it that the title of the thread means trees in general; I have usually noticed that once woodpeckers are drawn to a tree, the infestation and subsequent search by peckers for tasty insects kills the individual. I like the idea, though, that perhaps an infestation in one tree could foster a new generation of peckers that would keep the population of borers down in the whole forest, perhaps even limiting their spread.

-CK

I know what you mean. I could see how excessive foraging activity by woodpeckers on a tree could have a sort of girdling effect in the cambium layer beneath the bark and a tree dying from it. I like to think that woodpecker activity on an infested individual tree and the death of that tree due to foraging activity is better than a trees demise from borer activity, with the next generation of borers going on to compromise the health of and kill more trees, which is what is being reported by dendrologists who are studying the borers affect. I also hope that with more food (borers and borer grubs) the woodpecker population will increase until a natural balance is found, thus protecting tree populations as a whole.

I think you're onto something here about the balance of the ecology, James.  Even native borers could play a role, killing a few trees until it replenishes the soil, they become too numerous,  and the healthy trees survive.  They should provide tide over food for animals such as woodpeckers.  When a few trees are felled, the soil is replenished, the excess borers are eaten by other animals, and the healthy trees remain because the unhealthy ones were culled.

John S
PDX OR