Variety is the spice of desert bird life: foundation plant species provide habitat heterogeneity for bird communities in the Mojave Desert.

Plants provide habitat and resources to the desert animal community. However, these interactions are species specific and can depend on season. I tested the hypothesis that birds use different foundation species in deserts as microhabitat, and birds shift associations by flowering and fruiting life-stages. I used line transects to record habitat associations of birds at a protected site in the Mojave Desert. I found that the bird biodiversity and behaviour were not equally represented across all microhabitats or season. Diversity of birds and territorial behaviors were significantly greater at shrubs microhabitats in spring. Shrubs likely primarily provided structural heterogeneity for the avian community to use as perches, nests, and other non-trophic services because foraging and consumption were observed less often. Bird biodiversity was greater at cacti than at open summer microhabitats, which supported the least bird biodiversity. Non-trophic interactions with plants are important for maintaining local bird diversity in deserts.

Transcript

1. Variety is the spice of desert bird life: foundation plant species provide habitat heterogeneity for bird communities in the Mojave Desert A Master’s Thesis Malory Owen August 2020 York University
2. Habitats are important. Microhabitat Macrohabitat
3. Microhabitats mean Heterogeneity Jorgensen 2004 Price 1978 Microhabitat is determined by a single niche dimension
4. Facilitation happens at microhabitats Stachowicz 2001
5. But foundation species are the stars of the facilitation show He et al. 2013 Callaway and Walker 1997
6. Why are bird-plant interactions worth studying?
7. Research Objectives • Hypothesis: Birds associate with different foundation species in deserts as microhabitats and temporal shifts in plant flowering and fruiting changes the frequency and nature of these associations • Prediction 1: The abundance, richness, and diversity of a desert avian community is greater near foundation plants relative to open-gap microhabitats without a foundation plant. • Prediction 2: The bird-plant associations estimated by observed bird behaviours will vary across microhabitats (cactus, shrub, or open) and by season (spring versus summer) because of changes in plant and bird reproductive timing.
8. Methods: Study Site Sweeney Granite Mountains Desert Research Center
9. Methods: Study Species Buckhorn Cholla Cylindropuntia acanthocarpa Mojave Yucca Yucca mohavensis Creosote Bush Larrea tridentata Black-throated Sparrow Amphispiza bilineata
10. • May & August observations • Two 500m transects • Record bird species, behavior, & microhabitat Methods: Experimental Design
11. Methods: Pre-Analyses • Five bird community composition metrics: • Species abundance • Species richness • Species diversity • Trophic guild abundance • Migratory class abundance • Five broad behavior classes: • Active movement • Inactivity • Cleaning • Territorial • Feeding
12. Methods: Statistical Analyses • Generalized Linear Models • Bird community metrics and bird behaviour frequencies • glm(counts~microhabitat*season + (1|survey) + (1|temp), family = quasipoisson, data = data_species) • Post-hoc comparing estimated marginal means • Exclusion analyses removing Black-throated Sparrows • Multivariate Analyses • Non-metric Multidimensional Scaling • PERMANOVA
13. Results: Bird Community Composition at Seasonal Microhabitats
14. Results: Bird Community Composition at Seasonal Microhabitats
15. Results: Species Specificity
16. Results: Behaviour Frequencies at Seasonal Microhabitats
17. Results: Multivariate Analysis
18. Why are spring shrubs important for birds and why do they support territorial behaviour? Lima 2009 Collins 1981; Beck and George 2000 Searcy et al. 2006 Wilkins et al. 2013; Cooney et al. 2018
19. What about cacti and open microhabitats? Koyama 2015; Ivey et al. 2020 Filazzola et al. 2020; Callaway 1998; Bonanomi 2011
20. Habitat Heterogeneity is Key
21. Moving forward
22. Thank you, to the Lortie Lab members Nargol Ghazian, Mario Zulianni, Jenna Braun, Steph Haus, Jacob Lucero, Calvin Cho, & Chris Lortie, to my examination committee Bridget Stutchbury, Amro Zayed, & Taly Dawn Drezner, to Jim Andre & Tasha LaDoux from SGMDRC, to the Anza Borrega Foundation & NSERC, and to my friends & family.