Saturday, June 7, 2014

Spring Migration Blitz Nets Record Numbers

How do they do it?  Millions of tiny songbirds migrate thousands of miles from their wintering grounds in Central and South America to their nesting grounds in North America each spring.  Studies show that they often take longer routes to take advantage of jet-stream patterns to save energy.

Blackburnian Warbler (photo:  Valerie Geile)

This spring brought many, many birds along the Mississippi River flyway to the mist nets at the World Bird Sanctuary (WBS).   A record number of migrating birds were banded at WBS from April 21 through May 12 this year.  Sixty different species were captured, and a total of 853 birds were encountered in all!  Last year’s total was 675 birds which was significantly more than the average of 300 birds per previous season.

Cerulean Warbler (photo: Linda Tossing)

Of the 60 different species banded, there were 23 different warbler species.   The most commonly caught were Tennessee Warblers (183) and Nashville Warblers (120), both numbers up from last year.  Special birds caught in the spring of 2014 include a Cerulean Warbler (the first ever caught at WBS), a Blackburnian Warbler, and a Wilson’s Warbler.

Wilson's Warbler (photo: Laura Bailey)

In a wooded ravine at WBS, banders opened 24 mist nets before sunrise daily for three weeks to see what birds might drop by.  These 10-foot high nets look like a combination of a badminton net and a Roman shade.  Since the nets are hard to see, birds fly into a net and drop into a pocket.  They are then carefully extracted, identified, measured, assessed, banded, and released.

The statistics collected were submitted to a database under the auspices of the Bird Banding Laboratory, part of the United States Geological Survey (USGS).  The USGS issues permits to qualifying banding organizations that place uniquely numbered bands on captured birds.  If a banded bird is recaptured, it is interesting to find out where it has been or how long it has been in our area.  The data accumulated from this study could be useful to monitor population growth or decline for various species, their life spans, migration paths, and survival rates. Changes in habitats for bird species may be reflected in capture numbers as well.  Banding is thus an important tool to further the understanding of bird populations.

Chestnut-sided Warbler (photo: Susan Eatoon)

Why would a bird leave comfortable territory to travel to parts unknown?  There is a greater chance of survival and success in finding food and shelter when there are separate breeding and wintering grounds.  In the spring a different food source becomes available in the new location and there is less competition for nesting sites.  With colder temperatures a return to warmer climes is necessary.  Change in day length, temperature, amount of food available, and genetic predispositions trigger migration.

Bird banders at WBS are dedicated to monitoring bird numbers in the St. Louis area.  They not only band daily during spring migration but they also band weekly throughout the summer and fall.  Northern Saw-whet Owls are captured during special nightly sessions in October.

If you are interested in observing or helping with the capture and banding process, public demonstrations are conducted every first and third Thursday of June, July, and August near the wildlife hospital at WBS.  The World Bird Sanctuary is located off the Highway 44 North Outer Road, accessed at the intersection of Highways 44 and 141 near Valley Park.

For more information click here

Submitted by Mary Elise Okenfuss

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