Saturday, May 16, 2015

Red Headed Woodpeckers



One of my coffee-drinking buddies laments the decline of the Red Headed Woodpecker.  He is in his eighties and he remembers the Red Headed Woodpecker as being a rather common bird.  Now, he says they are quite rare.

As the "kid" I am the designated "computer" guy.  The internet supports what my buddy says.  Populations of the Red Headed Woodpecker have declined to 10% of pre-1960 levels.

Peak populations of Red Headed Woodpecker peaks in fairly dry areas with large populations of cattle.
One of the interesting factors about RHWs is that 2/3s of its food is plant based.  That is unusually high for a woodpecker.  RHWs collect and cache "hard mast", that is, acorns, hazelnuts, and other nuts and seeds.  There is little information regarding max/min sizes of mast.  Nor is there information regarding how tough of a shell RHW can deal with.  But all sources are clear, RHW like acorns and beechnuts.  The fact that RHW can access a greater diversity of foods, and because they can store them, suggests that the primary reason for their rarity is NOT food related.

A second interesting factor is that RHW seem to prefer open forest floors.  This may relate to the ability to forage for hard mast without losing the ability to scan for predators.  It is now considered bad practice to graze livestock in woodlots.  It is devastating to the wildflower populations.  However, it was optimal for RHW.  They could noodle through manure patties for worms and beetles.  The open forest floors also made it safer for them to forage for hard mast.

A happy medium may be for small "ranchers" to use woodlots as drought buffers.  I know that I was able to feed a flock of 12 ewes + lambs for a week when a Weeping Willow disintegrated and the sheep were able to browse on the tops.

Snags


The biggest factor in the decline of Red Headed Woodpeckers is probably the lack of suitable nesting sites.

Red Headed Woodpeckers typically excavate a new nest cavity each year.  They are not very capable excavators so they pick trees that are punky to the point of being almost completely rotten.  Take a punky, standing tree and then chisel a cavity into it.  That double-whammy to the structural integrity of the tree does not bode well for the longevity of the snag.  The practical implication is that a viable RHW habitat must have a constant recruitment of new snags.  

Not all snags are created equal.

In most of lower Michigan, that implies a 10%-to-20% canopy of multi-aged soft maples (Acer saccharinum) and/or Cottonwood (Populus deltoides).  In urban areas, Weeping Willow can be added to this list.  These species rapidly produce large diameter trunks and limbs.  Little birds can nest in small cavities.  Medium and larger birds need bigger cavities....and girthy trees to contain those larger cavities.  Both soft maple and Cottonwood quickly become "girthy". 

Of the two species, soft maples are more likely to have a range of ages.  Cottonwood is the classic pioneer species.  It is far more likely to exist as a stand of a single age class within a given habitat.  Cottonwoods offer famine-feast-famine for woodpecker nesting sites.



Another option involves lightening damaged Northern Red Oak and/or White Pines at higher elevation or decrepit Sugar Maple in "sugar bushes".  One common factor in these species is that they do not have durable heartwood.  White Oak may be wonderful mast producing trees but they are unlikely hosts for Red Headed Woodpecker nests because the heartwood is extremely hard and rot resistant.

An advantage of lightening damaged trees is that they remain standing for  a long time.  Dead elm and ash trees, on the other hand, tend to rot at the base and fall over before the tops have become punky enough to be desirable to Red Headed Woodpeckers.

Fashion


The current fashion on woodlot management recommends the removal of trees that are approaching senility.  Any wood that rots is considered a waste.  Part of this trend is due to energy prices.  Many people started heating with wood when the price for a gallon of heating oil was more than 1/3 the minimum hourly wage.

Another trend that made snags rarer was the increased use of wood chips for landscaping mulch. Combine increasing property taxes, increasing property assessments and more avenues for converting snags (waste-wood) into folding money and you have a train-wreck for species that depend on benign neglect of woodlots.   Even the smallest stick of waste-wood can be chipped for fuel or mulch.  This is rough on cavity nesters and birds that eat grubs, beetles, worms and such that live in rotting wood.  Red Headed Woodpeckers are both.

An overgrown pothole with mature Black Willow and Cottonwood trees.
Another factor is that organizations like Pheasants Forever recommend clear-cutting "pot-holes" to eliminate predator loafing spots.   That not only disadvantages hawks.  It also eliminates snags that are useful to cavity nesters.

Clearcutting potholes increases grain yield as the grain, both east and west of the pothole, is not shaded by the trees.  Further, during times of high crop prices, farmers find it economically compelling to drain the potholes so they can be plowed and planted to grain.  Then the potholes are gone.

Additional reading HERE.

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