The Effects of Global Warming on the Migratory Behaviors of Birds
All the living beings in the world, including birds, perform analysis and scanning of the environmental conditions of a place where they are opting to stay or making home at that place. However, the rotation of the Earth and the change in the altitude of the sun’s position result constant changes in seasons and environmental conditions. If the animals want to reproduce and even survive, they should adapt to the changing conditions of environment. The most common response to this phenomenon is migration. Many animals practice migration, but this practice has been especially studied in birds. However this paper will mainly discuss the changes in these migrations patterns as a result of global warming. Global warming has not only changed the climatic conditions of many places of the Earth, but also affected the availability of food and water for these animals. Mainly, the changes in the migratory behaviors of birds will be discussed in this paper.
Phenomenon of Bird Migration
Birds can fly long distances, which makes them the most mobile group of living beings. Therefore it is not very surprising to observe the phenomenon of migration in birds. Migration is one of the most important parts of the life of birds and a very difficult journey. When the living conditions of a region become unstable for these birds, they migrate to another region of the world, even if it is very distant and is relatively habitable. This mechanism of birds allow them to breed in more stable regions of the world, provide them with food and overcome the climatic barriers such as snowfalls and heavy rain falls (Berthold, Control of bird migration, 1996).
Global Warming – Change in Earth’s Environment
Global Warming is the phenomenon of the change in climate of the regions of the world as a result of increase in air pollution. This increase in air pollution is solely the result of increased human activity and burning of the fossil fuels. The amount of the greenhouse gases has been increased in the environment which has caused the greenhouse effect. The changes in the environment due to global warming may accelerate the current patterns of migration in birds which has already been observed in some of the species (Berthold, 2001). With the change in environment and the living conditions for birds, migration from that geographical location to another is the only way for the birds to survive.
Variable Shifts in spring and autumn Migration
The recent studies have revealed that in the last decade there have been advancements in the timing of bird migration in spring season. These results are especially valid for the continent of Europe. This is because the rate of change of climate warming has been higher in Europe than in America and other continents. However, the results of bird migration for autumn have not been consistent. The spring migrations in the 46 year period research revealed earlier departures of the birds. These changes were significant in this research period for spring but this was not the case for autumn (Buskrik, Mulvihill, & Leberman, 2009).
According to a recent research performed by Buskirk et al, the migratory period for the birds have lengthened because of global warming and because the late phases of migration were not changed. The research results also showed that the early phases of the migration in birds became earlier which caused significant changes in the time between migrations. The biggest revelations of the study were that the changes in migration timings each year showed positive correlations with the temperature recorded in the local regions. Hence, the study proves that as the temperature across the regions increase, the migration trends in birds also change. However, it was difficult to draw any conclusion as the migration trends varied among the different species of birds over the dataset (Buskrik, Mulvihill, & Leberman, 2009).
Breeding Distributions of North American Birds
Since the late nineteenth century, the mean surface air temperature has increased, on a global basis, between 0.4 and 0.8 degrees Celsius. The greatest rise in the level of warming has been noted in the seasons of winter and spring in the continental regions of the northern hemisphere. According to the research conducted by Hughes in 2000, there have been evidences that changes in climate cause changes in adaptation, physiology and distribution of the living beings (Hitch & Leberg, 2007).
Recently, these have been rumors that due to the recent changes in the climate, because of global warming, there have been geographic changes in species distributions to the regions which are cooler. This hypothesis was tested through a research conducted by Hitch and Leberg which revealed that out of the total 27 bird species examined nine showed a significant migration trends toward northern regions. The northward shifts of the bird’s distributions were proved by the collection of data of almost 26 years. Only two of the total species shifted southwards even though they were in the northern margins. The area shifted towards the north of all the southern birds was calculated as 2.35 km/year (Hitch & Leberg, 2007).
These results have been in consistency with the results of observation of Thomas and Lennon which showed that the breeding grounds of the southern birds have been shifted towards northwards over the last several decades. The cause of these shifts has been cited as the climatic warming or global warming. No other factors have been expected to cause the changes in distribution of breeding grounds of the birds towards the north. These northward shifts are not expected to be a result of population expansions, changes in land use or improvements in species detection. If this was the case, the species with northern distributions would have shown southward shifts. Birds are extremely mobile and this is the reason that they move quickly in response to changes in climatic conditions. Therefore in response to greater levels of global warming, most of the birds adjust their locations (Hitch & Leberg, 2007)
Staying Longer in Canada
In Canada, the birds can be observed to stay inlands much longer in 2010 than they used to stay in the earlier decades. According to a documentary by Worldnews, the climate change might delay migration of these birds and throwafter the natural timings. A bird enthusiast in the documentary recites his observations which tell us that some species of birds are staying longer in Canada and the scientists are noticing new phenomenons. The scientists are still confused whether this phenomenon is the result of climate change or something else. However, all the scientists do agree that this change in migration behavior could be the third level effect of global warming. Canadian naturists have also explained that the birds who are staying longer will be faced with more predators, food shortages and even new competitors (Gillich & Christianson, 2010).
The head curator of life sciences at the Royal Saskatchewan Museum refers to the climatic requirements of the birds as an “environmental envelope” for which they are searching in different regions. This is their primary requirement for staying alive and finding their food. Thse conditions in their environmental envelope are ideal for them, hoever, if they are not able to find these conditions, the lives of the birds will be in danger (Gillich & Christianson, 2010). Ornithologists have long been studying the changes in individual species and the changes in migratory arrival times that have been quite consistent with the climatic warnings. However, the ornithologists have still not been able to make generalizations about the changes in the migration patterns and the global warming (Jones, 2007)
North to South and Staying Behind
The easiest migratory pattern for us humans to understand is perhaps the long distance migration southwards from north. For example, Barn Swallows can live in most of the Eurasia and North America in the summer time and feed on the seasonal flying insects in living in the crops. However, the winter weather is so severe, over most of their breeding range, that the chances of the birds surviving are almost zero. This forces these birds to move out to the southern areas where they can continue to feed on insects. With the changes in climate due to global warming, these birds are staying longer in North American and Eurasian territories (Elphick, 2007).
Birds have no reason to move out if they have food supplies available all year round and the climate matches their requirements all year long. To overcome the harsh climates, these bird species have to fly to the extreme south. However, the Barn Spallows in the Southern states a do not require to move at all as they do not experience severe winters and hence they stay in their breeding range (Elphick, 2007). The southern states of the United States are sensitive to the effects of global warming and hence the people in these states are observing drying-up of land, lower productivity of the land and depletion of forests. These changes in the environment because of the change in climate are causing the birds to migrate at different times and to different desrinations (Pew Center, 2010).
The Dead Sea and Migration Trends
The major route of bird’s migration between Europe, Asia and Africa is through the Dead Sea. Millions of birds make twice a year journey across the Dead Sea today. The habits of these birds have not changed but yet something else has. The migrant birds’ calendar has been threatened to disrupt by the global warming. The main issue is that the birds are correct on their part, when they feel the time has come to migrate from one place to another, they do so. The birds observe the time of migration, however, the weather conditions are not very predictable as they used to be earlier. This has been a direct result of change in the climate. The birds used to tackle the problems of migration in the earlier times which was a tough job. In the current scenario, the birds have to come across additional problems as well such as droughts, changes in food supply, habitat and unseasonable storms. However, it is still too early to comment whether this change in bird’s migrating behavior will prove to be permanent or will they risk their extinction (Moss, 2003).
The Movement Patterns and Weather
According to a research, the weather or climate is a prime factor in the movement and migration patterns of birds. Wind speed, pressure, temperature and cloud cover influence the avian movement patterns. As we have witnessed a drastic change in the climate, the changes in wind speed, pressure, temperatures and cloud covers have also changed and hence the migration patterns of the birds too are changed. On the clear nights, larger flocks of birds were observed and the windy days also detected larger passages. In order to secure a prime a prime breeding ground, the birds have to complete their journey in a specific time period, after which their efforts would result to be futile (Thomas, 2008).
Perish or Adapt?
Birds are now forced to either adapt to the changing climate or get extinct in the new evolving scenario. Some of the species of birds have already selected and tried out new breeding grounds. Instead of breeding in Mediterranean Coast, a Blackcap Warblers subpopulation has started to winter in England (Alembath, 2009). In Britain, some birds even have changed their breeding seasons. Earlier, never would a bird take risk of starting its family in midwinter (Gienapp, 2008), but now there are cases of songbirds having their breeding seasons before the spring season. This behavior is becoming very common new because of the change in climate and the gradual increase of world temperature (Owen, 2003). The main reason behind this is that the temperatures rise earlier because of which the food supplies increased earlier for the chicks and the temperatures became favorable for birds (BirdWatch Ireland, 2004).
In order to adapt to the changing environment, some of the birds perform partial migrations because of the disruptions in weather. These partial migrations also have increased and are observed at a greater rate than before (Berthold & Terrill, 1991). The reproduction and survival risks of the migrating birds are associated with the timing of migration. Hence, the change in climatic conditions around the world might have significant consequences of life history for these migrating birds (Forchhammer, Post, & Stenseth, 2002).
The Final Consequences
Predictions of widespread extinctions have been anticipated by the scientists as the final ecological consequence of the change in climate. According to a research performed in the United States, it was revealed that as the distribution size decreased, extinction vulnerability increases. The results also showed that there will be high predictions of extinctions among the narrowly distributed species (Mark, Louis, Anantha, N., & Raymond, 2006).
The changes in migratory patterns in birds have been proved to be resulting from the change in climatic temperatures. Birds are flying late to their migration destination as compared to the earlier years of the century. The past researches have shown that birds’ breeding season have also shifted. However, this is not the case in all of the birds. Some birds did not show a change in migration pattern at all while others have shown a significant change. May be new researches can reveal better results in the next decade about the migration patterns as climate changes.
Alembath, M. (2009, April 15). Global Warming and its Impact on Bird Migration. Retrieved May 12, 2010, from Suite101.com: http://wildlife-conservation.suite101.com/article.cfm/global_warming_and_its_impact_on_bird_migration
Berthold, P. (2001). Bird migration: a general survey (Second Edition ed.). New York: Oxford University Press.
Berthold, P. (1996). Control of bird migration (First ed.). London: Chapman and Hall.
Berthold, P., & Terrill, S. (1991). Recent Advances in Studies of Bird Migration. Annual Review of Ecology and Systematics , 22, pp. 357-378.
BirdWatch Ireland. (2004, January 20). Recent changes. Retrieved May 12, 2010, from Migration Watch: http://www.bto.org/migwatch/text/info/changes.htm
Buskrik, J., Mulvihill, R., & Leberman, R. (2009). Variable shifts in spring and autumn migration phenology in North American songbirds associated with climate change. Global Change Biology , 15, 760-771.
Elphick, J. (2007). The Atlas of Bird Migration: Tracing the Great Journeys of the World’s Birds. London: Marshall Editions.
Forchhammer, M., Post, E., ; Stenseth, N. (2002). North Atlantic Oscillation Timing of Long- and Short-Distance Migration. Journal of Animal Ecology , 71 (6), 1002-1014.
Gienapp, P. (2008, September 15). Climate Change Impacts: Birds. Encyclopidia of Life Sciences .
Gillich, J., ; Christianson, A. (2010, April 4). Global Warming in Changing Bird Migration. Retrieved May 12, 2010, from Worldnews Network: http://article.wn.com/view/2010/04/21/Global_Warming_is_Changing_Bird_Migration/
Hitch, A., ; Leberg, L. (2007). Breeding Distributions of North American Bird Species Moving North as a Result of Climate Change. Conservation Biology , 21 (2), 534-539.
Hughes, L. (2000). Biological consequences of global warming: is the signal already apparent? Trends in Ecology ; Evolution , 15, 56-61.
Jones, J. (2007, May). Review: Canaries in a Global Coal Mine? Ecology , 88 (5), pp. 1337-1338.
Mark, W., Louis, R., Anantha, M., N., S., ; Raymond, J. (2006, July). Predicting Extinctions as a Result of Climate Change. Ecology , 87 (7), pp. 1611-1615.
Moss, S. (2003, Movember 3). Weatherwatch. The Guardian , p. 22.
Owen, J. (2003, January 3). Early Birds: Is Warming Changing U.K. Breeding Season? Retrieved May 12, 2010, from National Geographic News: http://news.nationalgeographic.com/news/2003/06/0603_030603_christmasowls.html
Pew Center. (2010). Forests ; Global Climate Change: Potential Impacts on U.S. Forest Resources. Arlington: Pew Center.
Thomas, P. (2008, December). Factors Influencing Avian Movement Patterns Around Proposed Ridgeline Wind Farm Sites In British Columbia. The University of Northern British Columbia . Ottawa, Canada: Heritage Branch.