According to an article by the British Broadcasting Corporation (BBC), climate change refers to the shift in average weather conditions. The increase in climate change is chiefly caused by human-led activities: operation of factories and transport as well as the burning of fossil fuels. The world is 1.1°C warmer when compared to the 1900s and atmospheric CO2 has increased by 50%, states the report. These kind of changes could have devastating effects on life as we know it.
Birds are of immense ecological importance; they aid, in various ways, in maintaining the balance of the ecosystem and contributing to the propagation of life on earth: pest-control, pollination, seed dispersal, nutrient, scavenging, nests (serve as a shelter for other organisms), participating in nutrient cycle; reports a team of researchers from Midewin National Tallgrass Prairie, USA, and University of Missouri-St. Louis, USA, in their paper, published in Annals of the New York Academy of Sciences.
A recent study by a team of more than 100 researchers spanning across various countries, published in Proceedings of the National Academy of Science (PNAS), highlights the fact that though significant research has been done on investigating the effects of climate change on the timing and migration of bird breeding, there isn’t enough work, with consistent, reliable results, regarding its effect on laying dates and offspring production.
Hence, this diverse team set out to investigate changes in offspring production in different bird populations around the world using meta-analysis: an approach that involves statistical analysis and combines the results of previous studies. The duration of their study is 50 years (1970-2019): during which there has been a 1°C increase in global temperatures,
The paper refers to offspring production as the number of offsprings (fledglings) produced by a breeding female in one year when monitored during the breeding season. Their research involved studying 201 populations of 104 species of birds belonging to the categories of land birds, freshwater species, and seabirds, in protected (with >50% of the area under legal protection) and non-protected areas. Their minimum study period was that of 15 years where they could gather data for at least 10 breeding seasons.
The study’s results show a decline in the overall offspring production of birds from around the world over the past 50 years. The authors mention that even though the decline seems to be small, its effect is significant as it can lead to a bigger reduction if we think in terms of decades. In addition, the results revealed that 56.7% of the populations showed a decline in offspring production, whereas the rest showed an increase in the same.
The researchers pointed out that the birds whose offspring production declined were relatively larger and migratory, whereas those with increased production were small and nonmigratory (sedentary). Larger birds might respond slower to climate change owing to their lower fecundity (ability to produce many offsprings), extended maturation, and longer generation time; and a smaller body size is favored by natural selection in warming conditions, state the authors.
The results also suggest that nonmigratory, especially smaller, birds are capable of adjusting to local climate change and may benefit from temperature increase; and migratory birds (excluding the smallest) on the other hand may suffer.
The authors further believe that offspring production and climate change is governed by complex interactions with ecological as well as history traits of species. They think that future research should focus on deciphering the cause of nest failures to have a better understanding of offspring population decrease.
