Siberian Jays and Climate Change

Already in 1964 Arne Blomgren speculated that the perceived range shift of the Siberian jays could be connected to recent changes in climate. However, in spite of the Siberian jays being a well-studied species, the topic of how it will be affected by climate change has not been researched in detail, and a search on the Web of Science (8 January) using the the search terms "Siberian jays" and "climate change" only came up with four papers. One of these papers report fossil evidence of a southward shift during glacial expansions in Scandinavia (Holm and Svenning 2014).

Two papers concern the ability of species to evolve in response to climate change. Gienapp and Merilä (2014) studied changes in body mass over time in a population of Siberian jays, and attempted to connect this to climatic factors. They detected a drastic decrease in weight over the first two decades of the study with a subsequent increase in weight over the last decade of the study. While body weight was found to be highly heritable, most of the temporal change in body weight appeared to be due to plasticity rather than evolution. They did not manage to find a clear connection between any environmental variable and the changes in body weight, and thus the effect of climate change on body weight remains to be further clarified. The paper by Merilä (2012) discusses the ability of species to evolve in response to climate change with a wider lens, and uses Siberian jays as an example of a species where body weight has changed over time, but still without a proven connection to climate change.

Two different studies (Eggers et al. 2005; Layton-Matthews 2015) found that breeding success increase with increases in spring temperature. This may be explained by reduced thermoregulatory costs (which also affects provisioning trip rate, which in turn may influence the conspicuousness of the nest to predators) and also by food sources becoming available faster (Layton-Matthews 2015). This effect of temperature has also been found to interact with forest structure, but in an equivocal manner. Eggers et al. (2005) found that the positive effect of temperature on breeding success was larger in open (often managed) forest, while Layton-Matthews (2015) found that the relationship was stronger in the natural (usually denser) forest. Eggers et al. (2005) explained their findings by colder temperatures requiring more provisioning trips to meet higher energy demands, and this frequent movement to and from the nest may attract predators, but dense forest cover may mean that these trips are better concealed and the negative effect (through increased predation) is thus expected to be larger in open forest. Layton-Matthews' (2015) results on the other hand were explained by increased thermoregulatory costs in natural forest stands (Griesser and Lagerberg 2012), in that the warmer springs may help to compensate for these thermoregulatory costs. Layton-Matthews (2015) also found that the effect of temperature was mediated by population density, so that the effect was stronger at higher densities. This was explained by warm springs reducing competition between individuals.

This indicates that climate change (which will probably bring warmer springs to this area) will benefit Siberian jays. However, Layton-Matthews (2015) also identified a positive relationship between snow depth and survival in the jays. As snow depth is projected to decrease, this constitutes a negative effect of climate change on Siberian jays.

These two findings may thus have opposite effects on the viability of Siberian jay populations and it is not clear what the total effect might be. In my masters reasearch I will attempt to model the effects of projected decreased snow depth and increased spring temperature on a population of Siberian jays in Arvidsjaur, Sweden, to get a better grip on how climate change may affect this species. You can read more about my project work here.

References:

Blomgren, A., 1964. Lavskrika. Bonniers.

Eggers, S., Griesser, M., Andersson, T. and Ekman J., 2005. Nest predation and habitat change interact to influence Siberian jay numbers. Oikos 111: 150-158.

Gienapp, P. and Merilä, J., 2014. Disentangling plastic and genetic changes in body mass of Siberian jays. Journal of Evolutionary Biology 27: 1849-1858.

Holm, S.R. and Svenning, J.-C., 2014. 180,000 Years of Climate Change in Europe: Avifaunal Responses and Vegetation Implications. PLoS ONE 9: e94021.

Layton-Matthews, K., 2015. Environmental drivers of life-history traits and metapopulation dynamics. A model of the Siberian jay Perisoreus infaustus. MSc thesis, Universität Zürich.