Fig 1.
Proportion of diets composed of arthropods and other invertebrates (grey), ‘plants’ (orange, includes plants, fungi, and molds), and vertebrate tissue (blue).
The table is divided into two sections; free flying individuals (adults and juveniles; A) and nestlings (B). We further divide our observations according to the method used to characterize diet composition (direct observation, stable isotope, and stomach contents) and present the estimated proportion of each of the three food groups in the overall diet. Additional information on identified diet items from each food type are available in S1 Table.
Fig 2.
Characterization of food items as “likely cached” (light red), “either possible” (light purple), or “likely fresh” (light blue) for (A) adult Canada jay winter diet (n = 87 total observations) and (B) nestling diets using direct observations, stomach contents, and metabarcoding (n = 125 total observations). Allocation to the three categories was based on life history characteristics of food items and environmental conditions at time of observation or sample collection. The total number of food items in each of the three “cached” vs “fresh” categories are displayed under “All Food” and designations for the three major food groups (arthropods, plants, and vertebrate tissue) individually are also displayed.
Table 1.
Pros and cons of different diet analysis techniques compared in our analysis.
Our table outlines potential benefits and drawbacks of using each diet analysis technique we compared in our manuscript. Each diet analysis technique has clear advantages and potential disadvantages that should dictate when a specific approach would be most beneficial to use and when it should be potentially avoided. Study design and the purpose of the study should be considered carefully before a particular approach is used.
Fig 3.
Direct observations made of Canada jays foraging on a wide range of food items.
A) Canada jay (boreal morphotype) in Algonquin Provincial Park, Ontario feeding on Amanita muscaria (Photo by Langis Sirois, November 5, 2018), B) Canada jay (Pacific morphotype) with yellow residue around bill from recent consumption of the slime mould (Fuligo septica) on Vancouver Island, British Columbia (Photo by Dan Strickland, August 1, 2020), C) Canada jay (boreal morphotype) in Algonquin Provincial Park, Ontario regurgitating Choke Cherry (Prunus virginiana) seeds on a date (January 20, 2020) when cherries would only be available as cached items (Photo by Michael Runtz), D) Canada jay in Algonquin Provincial Park, Ontario dismembering a recently caught shrew (Sorex sp.) (Photo by Ann Brokelman, August 27, 2016), E) Canada jay (Rocky Mountain morphotype) in Grand Teton National Park, Wyoming consuming a Saskatoon berry (Amelanchier alnifolia; fide DFB; Photo by Susan Elliot and used with permission from the Macaulay Library at the Cornell Lab of Ornithology (ML478606261), August 26, 2022). F) Canada jay stomach casting apparently consisting of arthropod exoskeletal fragments (Strathcona Provincial Park, Vancouver Island, British Columbia; Photo by Dan Strickland, June 26, 2021).