Fecal DNA metabarcoding helps characterize the Canada jay's diet and confirms its reliance on stored food for winter survival and breeding

Abstract

Accurately determining the diet of wild animals can be challenging if food items are small, visible only briefly, or rendered visually unidentifiable in the digestive system. In some food caching species, an additional challenge is determining whether consumed diet items have been previously stored or are fresh. The Canada jay (Perisoreus canadensis) is a generalist resident of North American boreal and subalpine forests with anatomical and behavioural adaptations allowing it to make thousands of arboreal food caches in summer and fall that are presumably responsible for its high winter survival and late winter/early spring breeding. We used DNA fecal metabarcoding to obtain novel information on nestling diets and compiled a dataset of 662 published and unpublished direct observations or stomach contents identifications of natural foods consumed by Canada jays throughout the year. We then used detailed natural history information to make informed decisions on whether each item identified to species in the diets of winter adults and nestlings was best characterized as 'likely cached', 'likely fresh' (i.e., was available as a non-cached item when it appeared in a jay's feces or stomach), or 'either possible'. Of the 87 food items consumed by adults in the winter, 39% were classified as 'likely cached' and 6% were deemed to be 'likely fresh'. For nestlings, 29% of 125 food items identified to species were 'likely cached' and 38% were 'likely fresh'. Our results support both the indispensability of cached food for Canada jay winter survival and previous suggestions that cached food is important for late winter/early spring breeding. Our work highlights the value of combining metabarcoding, stomach contents analysis, and direct observations to determine the cached vs. non-cached origins of consumed food items and the identity of food caches, some of which could be especially vulnerable to degradation through climate change.

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.

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).