Nest Tree Longevity Study
In October and November 2015 an inventory was conducted of red-headed woodpecker nesting trees at Cedar Creek Ecosystems Science Reserve (CCESR) that were confirmed to have active nests in them during the years 2008 to 2014. The nesting trees after the 2018 nesting season were again inventoried. Basically, trees that were reported to contain an active nest were sought and if found were noted whether they were still standing or had fallen. Trees that had a snag of at least 8 feet were considered to be still standing. During this period aluminum tree tags with the nest designation had been attached to the trees. An attempt was made to find these tags and it was noted when they were found. Dr. Jim Howitz’s notes on nesting trees had noted which trees were down. This was accepted as confirmation the tree was down.
The total number of nesting trees during the 2008 – 2014 nesting periods was 146. Of these, two trees’ data was unclear if they were indeed nesting trees. If these two trees (assumed down) are included, the number of trees that contained nests that were still standing as of November 30, 2015 was 71 or 49%. The number of trees confirmed down by locating the aluminum tree tag (or Dr. Jim Howitz had noted it was down) was 32 or 22%. Trees that were not located and assumed down was 40 or 27%. One tree was leaning against another tree at a 45o angle. This tree and the two trees, whose data was unclear, was 2% of the total.
In comparing the number of trees still standing for the nest year, there is a steady increase in the percentage standing (33%, 38%, 48%, 54%, 59%, 33%, 66%) from 2008 through 2014, except for 2013 when the number plummeted to 33%. The increase is readily expected because of the shorter time to be blown over, but there is no explanation for the sudden decrease in standing trees from the 2013 nesting year. Five trees broke off mid-height, but were considered to be still standing because a RHWO could still use the tree to nest in.
A final comment – no inventory after the 2018 inventory has been done. Also, the designation of the location of a few trees was unclear from the data and the tree tags. An attempt was made to clear up
any confusion, but a few errors could have been made. It is conceivable that some of the trees, assumed to be down, were still standing but the tree tag came off and couldn’t be found. One tree tag was found on the ground between two trees, so it was unclear which was the nest tree. However, they were both standing so it was counted as a standing tree. It is also possible in some cases that the gps coordinates were in error due to operator error in recording the numbers. This was found in a couple of trees, so fortunately the error could be corrected.
This data on the number of trees that have fallen since the start of the nesting studies is important in understanding the continued presence of RHWO’s in an area. The natural loss of dead trees can have a devastating effect upon a population, if the number of dead trees falls below an unknown density in an area. If this density falls below that threshold, the RHWO’s likely will move to an area that has the needed density of dead trees. This is the reasoning why the retention of dead trees or snags is considered to be one of the reasons that explain the woodpecker’s decline during the last 60 years. This is obviously exacerbated by the removal of dead trees by landowners who consider them unattractive or fear their falling will cause personal injury or property damage. Our data indicates that about half of the dead trees will naturally fall in 5 – 8 years after nests have been established in the tree. This fact shows the need to not remove these trees prematurely, it can potentially have an effect upon the future survival of red-headed woodpeckers.
Jerry Bahls