May 2007

What will global warming do to the birds around us?

by David Nowell

Everyone is beginning to talk about global warming and the effects it will have on our everyday lives such as warmer weather, less water, rising sea water levels, greater variability in weather and so on. If the weather is going to affect us this much, perhaps we should take a little time to think of the creatures that are entirely dependent upon the weather and other natural phenomena. Birds are typical. They are dependent upon weather for things such as:

* Food: their food is dependent upon the environment whether it is grain, fruits, insects or fish.
* Water: like humans, birds will die without water!
* Migration: birds have to migrate many thousands of kilometres at times to ensure they do not perish in the winter weather, and so that they will continue to have access to food.

Let’s take a closer look at just these three factors.

Humans can either buy their food at the nearest store or we can grow it for ourselves (if they are lucky enough to have access to some land). Birds are entirely dependent on food becoming available at the time when the need it. Therefore, if the environment changes, they may not have food at the critical times during their life cycle and this can affect things such as the breeding season, survival of their young or their ability to survive while migrating. People studying this phenomenon have shown that certain kinds of insects are now emerging at different times of the year (for example, earlier than normal due to the increased winter temperatures in some areas). This means that if insect eating birds do not breed earlier than normal, they may not have enough food for their young or the food could be exhausted before the young can fend for themselves. There are apparently also large changes taking place in sea bird populations. For example, in the northern Atlantic the certain birds’ food (smaller fish species) appears to be moving further north with the cooler water and the birds will now need to follow their food supply. This means they may have to abandon their traditional nesting sites and may not be able to breed in a given season.

Generally, changes in food availability and types of food, will result in changes in the occurrence and distribution of birds and some people are already convinced we are beginning to see this trend occurring in many parts of the world.

Water is essential to life as we know it and birds are no exception! Many bird species are entirely dependent upon water - not just to drink but also for their food (fish or water plants) and breeding habitat. Small changes in water availability could have large effects on bird populations - this means that species could change (some will disappear and new ones may appear). If there is a lot less water, water birds and wader populations could crash, but if there is more water (for example, rise in sea levels) then the number and variety of water birds and waders could increase. If regions are already dry and they start getting less rain or higher temperatures, then certain bird species may no longer occur in the region, while others could increase considerably. There are a small number of birds that get almost all of their moisture from the food they eat, but many of these species are not found in Europe.

Migration is dependent on many factors. Two key factors are the availability of water and food for most species - not all species migrate over long distances in a few days (some species are now known to fly continuously for more then 8,000 km without stopping long i.e. food only). Many bird species are dependent of food and water along the way to keep themselves going on their long journey. There is emerging evidence that some of the traditional migration routes may not be as favourable as they were due to reduced availability of water en route, for example, raptor migration over the Sahara region. This means that fewer birds can use such routes and/or that migrations times can change significantly and this then affects the birds’ ability to breed when they get to the normal breeding locations.

Although we do not understand all the information involved, it is well documented that many bird species time their migration to coincide with the availability of their food in the spring. Changes in temperature can change food availability patterns completely and this means birds need to adapt their migrations habits/patterns to ensure they are there when food is most abundant so that they can breed successfully?

This is just a superficial look at some of the key factors affected by climate change. Just imagine how confusing it is too many of our little feathered friends and how difficult life may become for some of them.

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