The change in trend may not, initially, sound like much, but it is significant in understanding how the climate impacts upon the natural world. What researchers have found is that birds are starting their migratory journey earlier and are reaching their breeding grounds, on average, one day earlier with each rise in temperature by one degree Celsius (this is expressed, alternatively, as an increase in the arrival time by 2.1 days per decade).
The impact of this early arrival, especially should the trend continue, is that birds may arrive to too early for key food sources to be available and this could impact upon populations. A secondary factor is that some types of birds may arrive at a breeding ground earlier than others, leading to increase competition for food resources. Most greatly affected are long-distance migrants, which are shown to be less responsive to rising temperatures. The consequence of the variations in arrival times at breeding grounds and increased competition for resources are that larger bodied species show greater advance over time compared to smaller bodied species of bird.
The Edinburgh University findings relate to species of birds across five continents. Speaking with BBC Nature, the lead researcher, Takuji Usui, explains: “Many plant and animal species are altering the timing of activities associated with the start of spring, such as flowering and breeding.”
The academic adds: “Now we have detailed insights into how the timing of migration is changing and how this change varies across species. These insights may help us predict how well migratory birds keep up with changing conditions on their breeding grounds.”
Thus the long-term aim of the research was to understand the impact of climate change on individual species and to provide a model for researchers to understand which species of bird might be under greater risk as temperatures continue to rise. The research included species that travel huge distances, such as the swallow and pied flycatcher, as well as those with shorter migrations, such as the lapwing and pied wagtail.
The research is published in the journal Animal Ecology. The research paper is titled “Temporal shifts and temperature sensitivity of avian spring migratory phenology: a phylogenetic meta-analysis.”
