The emerald ash borer (EAB) has killed 75 million ash trees in North America since 2002 (“Ville de Montreal”, 2015), causing Montreal to invest 15 million dollars over the next three years to deal with the infestation, and plant new trees (Laframboise, 2016). Predators of the EAB larvae include woodpeckers (Jennings et al., 2013). As the Island of Montreal is home to multiple species of both ashes and woodpeckers, we wanted to explore the relationship between these two organisms.
Emerald Ash Borer
The emerald ash borer is an invasive species to North America accidentally brought in from Asia (Daniel & Deborah, 2013). This green beetle feeds on the sap of ash trees and lays its eggs into the tree bark crevices. It infects all ash species (Daniel & Deborah, 2013). Damaged tree stands die within 1-4 years after infestation from this pest (“Emerald ash borer”, n.d). Since the EAB has no effective predator, forests with a high number of ash trees are likely to decrease significantly in the coming years.
Figure 1. Ash tree leaves on the left and ash tree bark on the right.
Ash trees (Fraxinus species) are large deciduous trees that grow on moist, well-drained soil in areas with direct sunlight. They have both opposite branching and leaves, and typically have 5-9 leaflets on a branch with smooth or toothed margins (Brown-Rytlewski & Thompson, 2003). They also produce wind dispersed samaras. Ash trees are easily identified by their bark; young trees have a relatively smooth, grey bark, whereas as they mature, diamond-shaped ridges develop.
Ash trees are common in many parts of the United States and Canada. On the island of Montreal ash trees are ranked the second most numerous species, with red ash being the most common (Rocha, 2015).
Figure 2. Most common species of tree in Montreal based on boroughs.
White ash trees are the predominant species of ash present in our study area, the Morgan Arboretum, a forest reserve located on the western tip of the Island of Montreal.
Woodpeckers peck at tree trunks for numerous reasons, including finding insects and building nest holes. They drum into trees to communicate, and can tap up to 8,000-12,000 times a day (Eberhardt, 1997). Woodpeckers are found in wooded areas worldwide with the exception of Australia (Helmut, 2016). They have a diversified diet with insects as their primary food source, followed by fruits, seeds, and nuts. Their bodies are designed to prevent damage to vital organs; they have powerful neck muscles and a thick skull that protects their brain and spinal cord (Spring L. W., 1965). The woodpecker’s tongue can extend, and is often covered with sticky saliva that allows them to catch more prey. They also have a strong, slightly curved bill that facilitates exposing insects in the tree bark (Zhou et al., 2009). At the Morgan Arboretum we observed damage on ash trees from the following woodpecker species: pileated, red-bellied, sapsucker, hairy and downy. Woodpecker characteristics vary, as shown in table 1.
Table 1: Characteristics of Woodpeckers Observed at the Morgan Arboretum
Factors Influencing Woodpecker Foraging Activity
Forest type, tree density and tree health each influence woodpecker activity in different respects. In fact, it has been shown that a larger diversity of woodpecker species can be found in deciduous forests than in coniferous forests (Myczko et al., 2014). Moreover, low density forests are possibly preferable for larger woodpecker species, because they lead to less hampering of movement and foraging (Myczko et al., 2014). However, the forest density also affects smaller species of woodpeckers, such as sapsuckers. According to Lawler & Edwards (2006), sapsuckers are more likely to nest in forests of low density. That study also showed that more sapsucker nests were observed in areas with a higher presence of fallen dead trees. This preference has also been shown for downy, hairy and red-bellied woodpeckers (Lindell et al., 2008). These results confirm that tree health is a factor affecting woodpecker activity. In a study by Flower et al., it was found that in EAB infested forests, bark-foraging birds, including woodpeckers, fed more often on ash trees, and preferentially fed on ash trees with canopy decline most likely linked to the EAB (Flower et al., 2014). No research addressing the relationship between woodpecker presence and ash tree bark quality has been conducted in the Arboretum.
EAB invasion is likely to reduce ash tree populations in the coming years. We wanted to understand the relationship between woodpeckers and ash trees before ash tree populations decrease significantly. Research by Myczko et al. (2014), and Lawler & Edwards (2006) shows that tree density influences woodpecker presence, hence we incorporated basal area as a measure of tree density into our research. We also decided to measure density of ash trees more specifically since they are affected by the EAB.
Research question: Does the density of ash trees and basal area affect the foraging activity of woodpeckers on ash trees at the Morgan Arboretum?
To carry out our experiment, we randomly selected six 50m2 sectors, and divided them each into four 25m2 plots. Two out of the four squares were randomly selected. In each plot, we measured the diameter of all standing trees at breast height (DBH) and also identified the specie of each tree, to be able to calculate basal area. Furthermore, for all of the ash trees we encountered, we used iNaturalist to record the position and number of each tree, as well as photograph the woodpecker damage whenever it was encountered. Finally, each ash tree was ranked on two scales; one based on their bark quality, and the other based on the severity of the woodpecker damage on the tree.
Table 2: Scale for Bark Quality
Table 3: Scale for Woodpecker Damage
Whenever possible, we noted the most probable woodpecker species, that had caused the damage observed on the tree. The data collected will be analyzed in order to see if there is any correlation between ash tree density, basal area and woodpecker damage in the Arboretum.
Here is a video describing our data collection process.
Ash tree identification guide. Retrieved October 24, 2016, from TreeRemoval.com, http://www.treeremoval.com/ash-tree-identification-guide/#.WA7RC5MrJE4
Brown-Rytlewski, D., & Thompson, R. (2003, May). Distinguishing Ash from other Common Trees. Retrieved from http://www.emeraldashborer.info/documents/E-2892Ash1.pdf. doi: 10.1146/annurev-ento-011613-162051
Bunn, B. Northern flicker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Northern_Flicker/lifehistory
Daniel, A. H., & Deborah, G. M. (2013, October). Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management. Retrieved from (1) https://www.colorado.gov/pacific/sites/default/files/atoms/files/Emerald%20Ash%20Borer%20Invasion%20of%20North%20America.pdf
Eberhardt, L. S. (1997). A test of an environmental advertisement hypothesis for the function of drumming in Yellow-Bellied Sapsuckers. The Condor, 99(3), 798–803. doi:10.2307/1370491
Emerald ash borer. Retrieved October 24, 2016, from Government of Canada, (1) https://www.nrcan.gc.ca/forests/fire-insects-disturbances/top-insects/13377
Flower, C. E., Long, L. C., Knight, K. S., Rebbeck, J., Brown, J. S., Gonzalez-Meler, M. A., & Whelan, C. J. (2014). Native bark-foraging birds preferentially forage in infected ash (Fraxinus spp.) and prove effective predators of the invasive emerald ash borer (Agrilus planipennis Fairmaire). Forest Ecology and Management, 313, 300–306. doi:http://dx.doi.org.proxy3.library.mcgill.ca/10.1016/j.foreco.2013.11.030
Jennings, D. E., Gould, J. R., Vandenberg, J. D., Duan, J. J., & Shrewsbury, P. M. (2013). Quantifying the impact of woodpecker Predation on population dynamics of the Emerald Ash borer (Agrilus planipennis). PLOS ONE, 8(12), e83491. doi:10.1371/journal.pone.0083491
Kube, R. (2014). Downy woodpecker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Downy_Woodpecker/lifehistory
Laframboise, K. (2016, April 5). Montreal pours cash into fight against emerald ash borer. Retrieved October 26, 2016, from News, http://www.cbc.ca/news/canada/montreal/montreal-emerald-ash-borer-budget-1.3521363
Lawler, J. J., & Edwards, T. C. (2006). A variance-decomposition approach to investigating multiscale habitat associations. USGS, 108(1), 47–58. doi:10.1650/0010-5422(2006)108[0047AVATIM]2.0.CO;2
Lindell, C. A., McCullough, D. G., Cappaert, D., Apostolou, N. M., & Roth, M. B. (2008). Factors influencing woodpecker Predation on Emerald Ash borer. The American Midland Naturalist, 159(2), 434–444. doi:10.1674/0003-0031(2008)159[434:fiwpoe]2.0.co;2
Mueller, H. (2016, September 19). Basic facts about Woodpeckers. Retrieved October 25, 2016, from http://www.defenders.org/woodpeckers/basic-facts
Myczko, Ł., Rosin, Z. M., Skórka, P., & Tryjanowski, P. (2014). Urbanization level and woodland size are major drivers of woodpecker species richness and abundance. PLOS ONE, 9(4), e94218. doi:10.1371/journal.pone.0094218
Ornithology, C. L. of. (2002). Cornell Lab of ornithology. Retrieved October 25, 2016, from http://www.birds.cornell.edu/wp_about/biology.html
Rocha, R. (2015, January 6). A tree grows in Montreal? Most likely a maple. Retrieved October 24, 2016, from Montreal Gazette, A tree grows in Montreal? Most likely a maple
Rognan, C. Yellow-bellied Sapsucker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Yellow-bellied_Sapsucker/lifehistory
Spring, L. W. (1965). Climbing and Pecking adaptations in some north American Woodpeckers. The Condor, 67(6), 457–488. doi:10.2307/1365612
Vierling, L. A., Vierling, K. T., Adam, P., & Hudak, A. T. (2013). Using satellite and airborne LiDAR to model woodpecker habitat occupancy at the landscape scale. PLOS ONE, 8(12), e80988. doi:10.1371/journal.pone.0080988
Ville de Montréal – borough Saint-Laurent – Emerald Ash borer. (2015, May ). Retrieved October 25, 2016, from Ville de Montreal, http://ville.montreal.qc.ca/portal/page?_pageid=8297,122605590&_dad=portal&_schema=PORTAL
Vyn, G. Pileated woodpecker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Pileated_Woodpecker/lifehistory
Wood, C. L. (2016). Hairy woodpecker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Hairy_Woodpecker/lifehistory
Wood, C. L. Red-bellied woodpecker. Retrieved October 25, 2016, from https://www.allaboutbirds.org/guide/Red-bellied_Woodpecker/id
Zhou, X. Q. Kong,C. W. Wu, Z. Chen. (2009). The Novel Mechanical Property of Tongue of a Woodpecker. Retrieved October 25, 2016, from Journal of Bionic Engineering 6 (2009) 214–218, www.sciencedirect.com/science/article/pii/S1672652908601262. doi: 10.1016/S1672-6529(08)60126-2
Belhumeur, R. (n.d.). Yellow-bellied Sapsucker Adult female [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Yellow-bellied_Sapsucker/id
Hanrahan, C. (n.d.). Hairy woodpeckers (Picoides villosus) scaling bark from trees [Digital image]. Retrieved from https://fletcherwildlifegarden.wordpress.com/2013/01/21/hairy-woodpeckers-picoides-villosus-scaling-bark-from-trees/
(n.d.). Downy Woodpecker Adult male [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Downy_Woodpecker/id
Jobes, W. (n.d.). Red-bellied Woodpecker Adult male [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Red-bellied_Woodpecker/id
(n.d.). Northern Flicker Male (Red-shafted) [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Northern_Flicker/id
Northern Flicker [Digital image]. (n.d.). Retrieved from http://www.wildbirdhabitatstore.com/index.php?option=com_content&view=article&id=79:northern-flicker-2&catid=2&Itemid=195
Oyer, B. (n.d.). Hairy Woodpecker Adult male [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Hairy_Woodpecker/id
(n.d.). Just Your Average Beautiful South Florida Day [Digital image]. Retrieved from https://palmbeachcountynaturally.wordpress.com/2012/03/23/just-your-average-beautiful-south-florida-day/
Smith, M. (n.d.). Pileated Woodpecker [Digital image]. Retrieved from http://www.audubon.org/field-guide/bird/pileated-woodpecker
Sharpe, M. (n.d.). Pileated Woodpecker Adult male [Digital image]. Retrieved from https://www.allaboutbirds.org/guide/Pileated_Woodpecker/id