Assessing the Success of Spruce Grouse Habitat Management in Adirondack Park, NY: Examining Changes in Invertebrate Prey Base

Charles Robinson

State University of New York

College of Environmental Science and Forestry

Background

Spruce grouse (Falcipennis canadensis) exist in low abundance in the Adirondack Park, and are listed as endangered in New York. Current estimates of spruce grouse populations in New York State indicate 100 or fewer individuals exist on the landscape (Ross and Johnson 2012). The New York State Department of Environmental Conservation (NYSDEC) has been monitoring this nonmigratory bird species and has recently begun a reintroduction program. Spruce grouse have been extirpated from many historic sites, and the NYSDEC are working to “achieve, protect and maintain self-sustaining populations of the spruce grouse” (Ross and Johnson 2012).

To achieve spruce grouse recovery, the NYSDEC have begun introduction efforts and habitat management to increase nesting habitat. In the Adirondack Park, NY, spruce grouse occur in lowland conifer forests dominated by spruce (Picea spp.) and tamarack (Larix laricina). Male spruce grouse tend to maintain territories in more mature stands which offer courtship display habitat, whereas females tend to brood in more dense stands (Ross and Johnson 2012). Spruce grouse have been extirpated from many historic sites, and the NYSDEC are working to “achieve, protect and maintain self‐sustaining populations of the spruce grouse” (Ross and Johnson 2012). Further information regarding spruce grouse or their status can be found in the Spruce Grouse Recovery Plan produced but the NYSDEC (http://www.dec.ny.gov/animals/89794.html)

To achieve the recover goals, the NYSDEC began habitat management to thin conifer stands cover to determine how to best replicate nesting habitat. Nesting occurs in young (44-49 year old) spruce and tamarack stands, with abundant ericaceous shrubs (Ross and Johnson 2012). Mechanical thinning was used to create experimental plots of varied stages of forest succession to determine which cut type best replicated nesting habitat.

Due to low abundance of spruce grouse it can be difficult to assess the success of management using nesting parameters. Therefore, the NYSDEC is using a variety of metrics including brood food availability to determine management success. The NYSDEC was interested in how closely invertebrate prey abundance and diversity on experimental plots match reference nesting habitat in the Adirondack Park. Invertebrates are an important prey item in the spring and summer diet (Ross and Johnson 2012).

This project was undertaken to aid the NYSDEC in its assessment of habitat management. I had three project objectives: 1) process the backlog of collected invertebrate samples from treatment sites; 2) conduct preliminary analysis on the effect of management type (cut intensity); and 3) create outreach material to be displayed at two public nature interpretive centers in the Adirondack region.

Methods

In Franklin County NY, nine (1 ha) plots of three harvest treatment types (Control, Light, and Heavy thinning) were established in 2008. The NYSDEC collected invertebrates using sweep net and pitfall methodologies over a 5-year period (2010 – 2014) that began two years post-harvest treatment. Due to missing 2014 data I used the 2013 sampling data for analysis.

Sampling occurred in all managed plots and at two reference sites, Willis and Kildare Road where spruce grouse are known to occur. Two (7 cm diameter) pitfall traps were place and left in place for 24 hours before collection. Sweep netting surveyed 9 m2 area adjacent to pitfall traps. A total of 1,300 samples were collected over the 5-year study period. I identified each invertebrate captured to the order level under a microscope and measured the total length. Biomass was assessed at the order level as individuals were not detected on the scale provided (accuracy = 0.0001 g). The common orders I identified included: Collembola, Coleoptera, Hymenoptera, Diptera, Odonata, and Hemiptera (Figure 1). Expert scientist review ensured proper identification to order.

I entered data into a master spreadsheet which has been provided to the host organization. Due to missing sample data, analysis of site level biomass by order was not possible. I used an unbalanced analysis of variance (ANOVA) to determine how biomass changes between the thinning treatments and reference sites for the two collection methodologies because there were more control plots (n = 4), then heavily (n = 2) and lightly (n = 3) thinned plots (Table 1). I used Tukey’s HSD post-hoc test to compare mean individual treatment level effects.

During the internship I kept in email and phone contact with my Sussman internship supervisor at NYSDEC as well as my graduate advisor at SUNY ESF to provide progress updates and solicit project advice.

Table 1: ANOVA sample size for each treatment and collection method (total sites = 11; 4 control plots, 3 light thinning plots, and 2 heavily thinned plots plus two reference sites at Kildare Road and Willlis).

Method Site

ControlLight Heavy Kildare Road Willis

Pitfall 12 12 8 37 40Sweep 33 28 19 37 38

Results and Discussion

I identified over 4,000 invertebrate specimens belonging to 21 orders using an Olympus compound microscope. The sweep net method collected more invertebrates (> 3,000) than pitfall traps (approximately 700). Sweep-netting collected high proportions of flies (Dipterans) and true bugs (Hemipterans), whereas pitfall methodologies resulted in collection of higher proportions of spiders and mites (Araneae) and beetles (Coleopterans) (Figure 2). Snow fleas (Collembola) were only found with pitfall traps while Hemiptera were only captured with sweep-netting. Hymenoptera (wasps, bees and ants) were found in roughly equal measure.

The ANOVA analysis of biomass between the thinning treatments was significant for both pitfall (P-value = 0.025) and for sweep net (P-value = 0.0002) methodologies (Table 1). The Tukey post-hoc test indicates that heavy thinning treatment was significantly different from the two reference sites and from the light thinning, and had higher invertebrate biomass for pitfall

traps in 2013 (Figure 3). Additionally, that heavy thinning treatment was significantly different from the Willis reference site but not from Kildare Road or the other treatments for sweep net methodologies in 2013 (Figure 4).

D

B C

E F

A

Figure 1: Common orders identified in the study sites: Collembola (A), Coleoptera (B), Araneae (C), Diptera (D), Hemiptera (E), Hymenoptera (F) and the author conducting invertebrate identification in the lab.

Figure 2: Proportion of invertebrate orders captured with two methods: pitfall traps (A) and sweep netting (B).

Figure 4: Invertebrate biomass across treatments and reference sites (Kildare Rd and Willis) collected with sweep net methodologies in the northwestern Adirondack Park, NY (2013)

Figure 3: Invertebrate biomass across treatment sites and reference sites (Kildare Rd and Willis) collected with pitfall methodologies in the northwestern Adirondack Park, NY (2013)

Cut intensity influenced invertebrate biomass for both collection methodologies. Plots that were heavily thinned had greater invertebrate prey biomass than other treatment levels and reference sites. However, the mean difference between the heavy treatment and the Willis reference site for pitfall traps was less than 1 g/m2. Likewise, for sweep-netting, the changes in biomass due to treatment effects was also less than 1 g/m2. Overall, the pitfall method resulted in higher biomass than did sweep netting, which may be a consequence of the longer time pitfall traps are active compared to sweep-netting, the size and number of invertebrate prey on the ground compared to in the air and shrub layer/understory. However, sweep-netting caught more individual invertebrates.

Different proportions of invertebrate orders were caught using the two methods. It is logical that sweep-netting would capture flying insect prey more readily than pitfalls, whereas pitfall trapping enables ground-dwelling invertebrates such as beetles to fall into the pitfall buckets. Further examination of the other metrics for successful nesting habitat management are needed to determine which, if any, thinning treatment best replicates high-quality spruce grouse nesting habitat.

During the summer spruce grouse in Alberta, Canada show an increase in invertebrate consumption (Pendergast and Boad 1970). Pendergast and Boad (1970) found Lepidoptera, Colleoptera, Hymenoptera, and Arachnida in the crops of spruce grouse. These taxa were among the most common found in our analysis (Appendix 1). This suggests that the invertebrate community composition in the Adirondacks include key prey items for spruce grouse.

I created a poster for public outreach to be displayed at the Paul Smiths Visitor Interpretive Center, Paul Smiths, NY and the Adirondack Interpretive Center in Newcomb, NY where tens of thousands of people visit annually (SUNY ESF and Paul Smiths College, unpub. data). The Edna Bailey Sussman Foundation was acknowledged in these products and will be in all resulting presentations.

Future Directions

The project supported by this internship will help provide insight on how to best improve habitat for spruce grouse nesting in the Adirondack Park. Through habitat improvement we maximize the success of reintroduction attempts, and ensure the health of the existing population.

It is unclear whether the thinning treatments increased the available biomass in a biologically meaningful way. Other metrics of successful nesting habitat management, such as vegetation assessment, may be more informative. Further analysis of invertebrate community diversity as well as the abundance of invertebrate orders is necessary. The NYSDEC will continue to monitor spruce grouse populations, and the success of both habitat management and reintroduction efforts.

Acknowledgements

I would like to thank the NYSDEC and my supervisor, Angelena Ross, for collaborating with me on this project. Additionally, I would like to thank my graduate advisor Stacy McNulty for her assistance and support. Special thanks to Dr. Glenn Johnson of SUNY Potsdam for providing identification quality control and lab support. This work would not have been possible without the support of the Edna Bailey Sussman Foundation.

References

Pendergast, B., and D. Boad. 1970. Seasonal changes in diet of spruce grouse in central Alberta. Journal of Wildlife Management 34:605–611.

Ross, A.M., and G. Johnson. 2012. Recovery plan for New York State populations of the Spruce Grouse. 86 pp.

Appendix 1: Invertebrate orders identified throughout the study period

OrderDipteraHemipteraAraneaeColeopteraHymenopteraLepidopteraPsocopteraCollembolaOrthopteraOdonataEphemeropteraOpilionesPlecopteraThysanopteraTrichopteraMecopteraMallophagaNeuropteraAcarinaIsopteraAnopluraSiphonapteraAchatinoideaMillipedeIsopodaother