Posts Tagged ‘migration’

Winged Migration- a Wonder of the World

November 30, 2009

Witnessing part of winged migration is always a highlight of my fall and winter visits to Roswell, New Mexico.

Unit 3, Middle Tract, Bitter Lake National Wildlife Refuge, Bitter Lakes Road off US 285, Roswell, Chavez County, New Mexico, USA.   Nov 27, 6:45 am.

Bitter Lake National Wildlife refuge covers over 24 thousand acres on the edge of the Chihuahuan Desert and the southern plains of New Mexico.  It is also at the bottom of the “central flyway” for migratory birds.  It is the first major wetland the birds migrating from Northern Canada, Alaska, the Arctic and coastal Siberia encounter where the water remains open all winter.  Birds follow the central flyway along the Rocky Mountain range until they encounter warmer climes for the winter.

Straddling the Pecos River and positioned overtop the seeping Artesian water aquifer, there is water  habitat available for marsh birds, ducks, geese, gulls, terns, shorebirds as well as eagles, hawks and falcons.

The morning of November 27th promised to provide us with many great wildlife viewing opportunities.  Upon driving into the refuge it was hard to ignore the loud, rattling, “Kar-r-r-o-o-o!”.   The shallow lakes that dot the refuge are dotted by thousands of birds of all shapes and sizes including the Lesser Sandhill Crane, Grus canadensis Canadensis. “Karooo” is occasionally punctuated by the sounds of hunters as the season for cranes, geese and ducks started the end of October.

Lesser Sandhill cranes are the smallest of the three subspecies at about 3-3 ½ feet tall with a wingspan of just over 5 ft.  They are known for their grey plumage and red foreheads.  It is thought that the Sandhill crane species has been around anywhere from 2.5- 10 million years.  That is over two times longer than next closest bird species.  They are expert soarers and hold their neck straight and legs back in flight.

We found a nice overlook and pulled out cameras and binoculars.  The assortment of water habitats are surrounded by the native grasslands, sand dunes, brushy bottomlands and small plateaus.  We hear a coyote barking in the distance and wait for the dusky-red sun to rise.  Soon it is obvious that the cranes are readying in the daily movement from the wetlands out to the surrounding fields to forage for grains and invertebrates.  Their great wing beats are like a dance as they stand in a foot or two of water.

Soon, many of the individual birds circling the ponds are forming into v-shaped flocks and are flying to the south along the river.  The flocks range in size from 8 to 45+.

These birds were once breeding, feeding and growing their chicks in the far north.   Some birds will remain here for the winter while others will disperse as far south as Northern Mexico.  Another refuge in Muleshoe, Texas boasts larger numbers.  A census count on Nov 19 counted 20,050 Lesser Sandhill cranes on the refuge and 765 off-refuge.  Sandhill cranes are the most abundant crane in North America.

It is a good hour after sunrise before any major activity of the thousands of birds in front of us.  Just as we are preparing to leave, a huge area of birds takes to the air.  It is hard to tell how the flocks are forming.  At a distance it seems more like a swarm or thin, dark cloud.  As they approach it seems like there have been several large flocks forming and some arms that stretch out to nearly 100 birds.  I managed to shoot a little video of this amazing fly over.

Lesser Sandhill Crane Flight

I would like to come back here and do some more focused observations.  It is hard not to get caught-up in the bigger picture event.  It is amazing to think that this movement of birds to the outlining fields happens every morning yet there are few people here to witness it, except hunters and an occasional birder or photographer and his dog.

I wonder what the cranes do in preparation for flying.  I noticed some wing-flapping and strutting among several birds.  Is this part of the routine or non-related?  Once aloft, what are the mechanics for flock formation?  What cues are they using?  I understand the cranes migrate in family groups.   Are these groups maintained in the winter?  I also understand that the birds trade the lead position as they draft off each other.  Is this spot available to every bird or just the experienced ones who know where they are going?

Research for another time…