Bird Migration

Bird Migration is an Amazing Phenomenon

Birds migrate to move to and from areas of abundant food and nesting sites and back to areas with milder winter weather and suitable habitat and food sources.  That means that in the spring and fall there are millions of birds moving north and south through our skies and landscapes.  These are critical times for the birds, exposing them to the dangers of navigating the huge land areas of human development, the exposure to predators, pollution, collisions, starvation, exhaustion, severe weather, and other dangers.

Cattle Egret

Migration periods bring strange birds to our province.  These birds have somehow been misled or driven off their normal flight paths to arrive here.  Just to mention a few of what has occurred in New Brunswick this year, we have a Cattle Egret (shown above) and a Western Meadowlark in Grand Manan this week (see photo below).  There has been a Burrowing Owl also on Grand Manan for about two months.  There has been a Crested Caracara in the Shepody/Alma area for a month.  There is a Fork-tailed Flycatcher on Miscou now and there was a Scissors-tailed Flycatcher at Cape Enrage recently.  There was a Swainson's Hawk and two Yellow-throated Warblers on Miscou last week.  All these species are well away from their normal areas.  

Incredibly just this week there was a bird found in Forteau, NL (on the Labrador coast of the Gulf of St. Lawrence) which is normally found from Finland east to Siberia and south to southern China.  This bird is a Yellow-breasted Bunting and has never been seen in eastern North America before.  There have been a few sightings of it over the years on the Aleutian Islands in the far western part of Alaska.

The Cattle Egret shown above should be in Georgia, Florida or Texas now, not in New Brunswick.  The   Burrowing Owl shown below should be in Florida, southwestern US or Mexico now, not here.  

Burrowing Owl

Why do birds make mistakes?  Why do they appear in places that are obviously way off their normal migration paths?  That is a difficult question and the answers are diverse.  Bad weather and severe wind storms play a big part.  Other reasons include disruption in their navigation systems by manmade structures and communication waves/towers, confusion within the bird itself related to its navigation system and many other reasons some of which are unknown.  There are other reasons related to the species population or circumstances which promote a behaviour called 'dispersal' which causes some of the birds to fly away from their normal flight paths.  This is an evolutionary strategy for the potential success or dispersal of the species.  

Western Meadowlark [Jennifer Pierce Photo]

In recent years great strides have been made in the research on bird migration.  In the 1940s the best technique for studying bird migration was to use telescopes to watch the birds as they passed in front of the moon.  Bird banding has been used for hundreds of years but since the recapture rate is only 1.3%, it reveals relatively little data.  In the 1950s they began to use radar to study the movement of bird masses during migration.  Since the 1970s scientists have been using geolocators and satellite transmitters.  Geolocators are small and can be used to track the movement of birds.  A Swainson's Thrush, for example, was tracked in its migration flight from Alaska to the southern Amazon region.  Satelite transmitters are heavy and can be used on birds no smaller than Mourning Doves.  

Scientists are now using nano tags which emit VHF radio waves and can be received by the Motus Network of towers.  They are very small and can be used on creatures as small as insects, making them very useful for birds.  To date 10,000 birds, bats and insects have been tagged.  This method has been much more successful than anything in the past.

But science is not done yet!  High Resolution Genetic Markers are also recently being used.  These measure DNA from feathers and by isotope analysis they can determine where the bird was hatched and where it has been.  It will be interesting to see what data can be gathered from this new technique.

These latter techniques have gathered a lot of data on bird migration.  We know a lot more about it now than they did in 1960 or 1970.  However, we have done little to help the birds and improve their migration success.  We need to preserve key stopover sites, to clear the night skies for them to successfully migrate.  We need to turn off our night lights on large buildings and other prime collision sites.  We need to protect flocks that are forced down during weather fallouts.  The key is education and action.  We must get the general population and cities and municipalities involved.  Four percent decline per year is way too much!!