Latitudinal gradients in the productivity of European migrant warblers have not shifted northwards during a period of climate change

Abstract

Aim As global temperatures have increased, many species distributions have exhibited polewards shifts, a trend that is predicted to continue in future decades. However, the mechanisms underlying such shifts are not well understood. Here we quantify the impact of large-scale variation in temperature on reproductive output within a group of migratory birds to assess the potential for future range changes. Location Western Europe.Methods We use data from captures of 350,000 individual birds, collected under constant effort ringing protocols from 1994-2006, to estimate productivity (percentage of juveniles caught) for seven species of migrant warblers (family Sylviidae) breeding in Europe in relation to spring temperature and latitude by fitting generalized linear mixed models. ResultsProductivity was highest at mid-latitudes for six of our seven study species and did not change significantly over the study period. Only one species (reed warbler, Acrocephalus scirpaceus) showed increased productivity at northern sites as expected. Six of the seven species also showed evidence for local adaptation, with productivity decreasing as temperatures diverged from the local mean. However, for three of these species the 'optimum' temperature was greater than the local mean temperature at the majority of sites. Main conclusionsThese results indicate that latitudinal gradients in productivity are likely to influence large-scale abundance patterns, but that adaptation to local climate conditions has the potential to constrain the rate of northward range shifts in many species.

Attributing changes in the distribution of species abundance to weather variables using the example of British breeding birds

“…Variation in these populations may be partly influenced by conditions on migration (Hewson, Thorup, Pearce‐Higgins, & Atkinson, ) or on their African wintering grounds (Johnston et al., ). However, we found strong spatial trends in abundance, which suggests there was likely also a strong impact of breeding season environmental variables for these species, including summer temperature, which is quadratically associated with spatial variation in willow warbler productivity (Eglington et al., ), and rainfall. Positive effects of temporal variation in breeding season temperature B time and negative effects of spatial variation B space —as shown for willow warbler—add weight to previous suggestions for poleward shift in distribution and negative impacts of warming on the breeding grounds in the south.…”

Rapid adaptive phenotypic change following colonization of a newly restored habitat

“…Smaller-bodied individuals are able to retain water at higher temperatures than large-bodied individuals30. Other ecological factors linked to climatic variation, such as resource availability, may also affect body size31. However, rising temperatures have previously been shown to correlate with a decrease in body mass1932, which strongly point towards a thermoregulation hypothesis.…”

“…However, rising temperatures have previously been shown to correlate with a decrease in body mass1932, which strongly point towards a thermoregulation hypothesis. The reed warbler has been singled out as a species that is very sensitive to global warming, which has resulted in a recent range shift northwards31. Malta is the southernmost location within the European reed warbler distribution33, and it has a dry subtropical Mediterranean climate, which is likely to have imposed a strong selective pressure on colonizers.…”

Disentangling the effects of spring anomalies in climate and net primary production on body size of temperate songbirds

“…A1), each site being monitored during 5.1 ( 3.9 SD) years (Dehorter and CRBPO 2015). Mist-netting of birds is most efficient in habitats with a low canopy (3-to-4 m high), so most CES sites are settled in shrublands, woodlands with dense understory, or reedbeds (Eglington et al 2015). A2), and there was no bias in site-specific average temperature or latitude (Supplementary material Table A1).…”