Migratory vertebrates shift migration timing and distributions in a warming Arctic

Abstract

Climate warming in the Arctic has led to warmer and earlier springs, and as a result, many food resources for migratory animals become available earlier in the season, as well as become distributed further northwards. To optimally profit from these resources, migratory animals are expected to arrive earlier in the Arctic, as well as shift their own spatial distributions northwards. Here, we review literature to assess whether Arctic migratory birds and mammals already show shifts in migration timing or distribution in response to the warming climate. Distribution shifts were most prominent in marine mammals, as expected from observed northward shifts of their resources. At least for many bird species, the ability to shift distributions is likely constrained by available habitat further north. Shifts in timing have been shown in many species of terrestrial birds and ungulates, as well as for polar bears. Within species, we found strong variation in shifts in timing and distributions between populations. Ou r review thus shows that many migratory animals display shifts in migration timing and spatial distribution in reaction to a warming Arctic. Importantly, we identify large knowledge gaps especially concerning distribution shifts and timing of autumn migration, especially for marine mammals. Our understanding of how migratory animals respond to climate change appears to be mostly limited by the lack of long-term monitoring studies.

Decadal migration phenology of a long-lived Arctic icon keeps pace with climate change

“…Climate-driven prey switching, however, has been associated with detrimental population effects in other pelagic predators ( 64 ). Differing rates and directions of phenology shifts in response to climate change are likely across a food web as a result of variation in motility (e.g., planktonic and benthic vs. nektonic organisms), phenological sensitivity, and life history ( 15 , 18 , 44 ). As a result, interactions among trophic levels may also change, limiting the ability for alternative community-level interactions (e.g., prey switching) to buffer the negative effects of temporally mismatched but preferred interactions, as was previously documented in parasitoid interactions for insects ( 65 ).…”

“…Meta-analyses suggest that few studies have examined phenological shifts in cetaceans and other marine mammals, presenting a major knowledge gap in the ability to predict responses to future climate scenarios ( 15 , 16 ). Even in well-studied regions, like the Gulf of Maine, very few studies have directly assessed long-term shifts ( 17 ) and have instead focused on establishing baselines in phenology ( 18 ).…”

Foraging habits of Northwest Atlantic hooded seals over the past 30 years: Future habitat suitability under global warming

“…It is difficult to predict whether hooded seals possess enough behavioural plasticity to meet climate‐induced challenges. However, even if hooded seals are sufficiently adaptable, a reduction in suitable foraging habitats will likely increase both intra‐ and inter‐specific competition for marine resources, as well as the risk of predation (Kovacs et al., 2011; Lameris et al., 2021). Accessibility to foraging areas might also be reduced if breeding or moulting areas do not also shift northwards (Shuert et al., 2022), although such a shift is likely for hooded seals.…”

Global temperature homogenization can obliterate temporal isolation in migratory animals with potential loss of population structure

“…Here we suggest another potential effect of the ‘homogenization of the world’: the loss of population structure in migratory animals. We reason that the phenological timing of these animals, moving between non‐breeding and reproduction sites annually, will become more synchronous because (i) populations of migratory species match the timing of migration with the phenology of resources in the reproduction, stopover or wintering areas (e.g., Alerstam et al., 2003; Rakhimberdiev et al., 2018) and (ii) migratory animals tend to adjust the timing of migration and reproduction with changing resource phenology (e.g., Charmantier et al., 2008; Gill et al., 2014; Gordo, 2007; Lameris et al., 2021). Migratory species often contain multiple populations or subspecies with different populations having spatially overlapping (sympatric) wintering, stopover, or reproductive areas (e.g., Alves et al., 2010; Bearhop et al., 2005; Briedis et al., 2016).…”